Absorption of proteins, fats, carbohydrates. Glycemic load

Digestion of proteins

Proteolytic enzymes involved in the digestion of proteins and peptides are synthesized and released into the cavity digestive tract in the form of proenzymes or zymogens. Zymogens are inactive and cannot digest the cells' own proteins. Proteolytic enzymes are activated in the intestinal lumen, where they act on food proteins.

In human gastric juice there are two proteolytic enzymes - pepsin and gastrixin, which are very similar in structure, which indicates their formation from a common precursor.

Pepsin is formed in the form of a proenzyme - pepsinogen - in the main cells of the gastric mucosa. Several pepsinogens with similar structures have been isolated, from which several varieties of pepsin are formed: pepsin I, II (IIa, IIb), III. Pepsinogens are activated with the help of hydrochloric acid secreted by the parietal cells of the stomach, and autocatalytically, i.e. with the help of the resulting pepsin molecules.

Pepsinogen has a molecular weight of 40,000. Its polypeptide chain includes pepsin (molecular weight 34,000); a fragment of a polypeptide chain that is a pepsin inhibitor (molecular weight 3100), and a residual (structural) polypeptide. The pepsin inhibitor has sharply basic properties, as it consists of 8 lysine residues and 4 arginine residues. Activation consists of the cleavage of 42 amino acid residues from the N-terminus of pepsinogen; First, the residual polypeptide is cleaved off, followed by the pepsin inhibitor.

Pepsin belongs to carboxyproteinases containing dicarboxylic amino acid residues in the active site with an optimum pH of 1.5-2.5.

Pepsin substrates are proteins, either native or denatured. The latter are easier to hydrolyze. Denaturation of food proteins is ensured by cooking or the action of hydrochloric acid. The following should be noted biological functions of hydrochloric acid:

1. pepsinogen activation;
2. creating an optimum pH for the action of pepsin and gastricsin in gastric juice;
3. denaturation of food proteins;
4. antimicrobial action.

The own proteins of the stomach walls are protected from the denaturing effect of hydrochloric acid and the digestive action of pepsin by a mucous secretion containing glycoproteins.

Pepsin, being an endopeptidase, quickly cleaves internal peptide bonds in proteins formed by the carboxyl groups of aromatic amino acids - phenylalanine, tyrosine and tryptophan. The enzyme hydrolyzes peptide bonds between leucine and dicarboxylic amino acids more slowly: in the polypeptide chain.

Gastricsin close to pepsin in molecular weight (31,500). Its optimum pH is about 3.5. Gastricsin hydrolyzes peptide bonds formed by dicarboxylic amino acids. The pepsin/gastricsin ratio in gastric juice is 4:1. In case of peptic ulcer, the ratio changes in favor of gastricsin.

The presence of two proteinases in the stomach, of which pepsin acts in a strongly acidic environment, and gastrixin in a moderately acidic environment, allows the body to more easily adapt to dietary patterns. For example, vegetable-dairy nutrition partially neutralizes the acidic environment gastric juice, and the pH favors the digestive action not of pepsin, but of gastricsin. The latter breaks down the bonds in food protein.

Pepsin and gastrixin hydrolyze proteins into a mixture of polypeptides (also called albumoses and peptones). The depth of protein digestion in the stomach depends on the length of time food is in it. Usually this is a short period, so the bulk of the proteins are broken down in the intestines.

Intestinal proteolytic enzymes. Proteolytic enzymes enter the intestine from the pancreas in the form of proenzymes: trypsinogen, chymotrypsinogen, procarboxypeptidases A and B, proelastase. Activation of these enzymes occurs through partial proteolysis of their polypeptide chain, i.e., the fragment that masks the active center of proteinases. Key process activation of all proenzymes is the formation of trypsin (Fig. 1).

Trypsinogen coming from the pancreas is activated by enterokinase, or enteropeptidase, which is produced by the intestinal mucosa. Enteropeptidase is also secreted as a kinase gene precursor, which is activated by bile protease. Activated enteropeptidase quickly converts trypsinogen into trypsin, trypsin carries out slow autocatalysis and quickly activates all other inactive precursors of pancreatic juice proteases.

The mechanism of trypsinogen activation is the hydrolysis of one peptide bond, resulting in the release of an N-terminal hexapeptide called trypsin inhibitor. Next, trypsin, breaking peptide bonds in other proenzymes, causes the formation of active enzymes. In this case, three types of chymotrypsin, carboxypeptidase A and B, and elastase are formed.

Intestinal proteinases hydrolyze peptide bonds of food proteins and polypeptides formed after the action of gastric enzymes to free amino acids. Trypsin, chymotrypsins, elastase, being endopeptidases, promote the rupture of internal peptide bonds, breaking up proteins and polypeptides into smaller fragments.

• Trypsin hydrolyzes peptide bonds formed mainly by the carboxyl groups of lysine and arginine; it is less active against peptide bonds formed by isoleucine.
• Chymotrypsins are most active against peptide bonds, in the formation of which tyrosine, phenylalanine, and tryptophan take part. In terms of specificity of action, chymotrypsin is similar to pepsin.
• Elastase hydrolyzes those peptide bonds in polypeptides where proline is located.
• Carboxypeptidase A is a zinc-containing enzyme. It cleaves C-terminal aromatic and aliphatic amino acids, and carboxypeptidase B contains only C-terminal lysine and arginine residues.

Enzymes that hydrolyze peptides are also present in the intestinal mucosa, and although they can be secreted into the lumen, they function primarily intracellularly. Therefore, hydrolysis of small peptides occurs after they enter the cells. Among these enzymes are leucine aminopeptidase, which is activated by zinc or manganese, as well as cysteine, and releases N-terminal amino acids, as well as dipeptidases, which hydrolyze dipeptides into two amino acids. Dipeptidases are activated by cobalt, manganese and cysteine ​​ions.

A variety of proteolytic enzymes leads to the complete breakdown of proteins into free amino acids, even if the proteins were not previously exposed to pepsin in the stomach. Therefore, patients after partial or partial surgery complete removal The stomach retains the ability to digest food proteins.

Mechanism of digestion of complex proteins

The protein part of complex proteins is digested in the same way as simple proteins. Their prosthetic groups are hydrolyzed depending on their structure. The carbohydrate and lipid components, after they are cleaved from the protein part, are hydrolyzed by amylolytic and lipolytic enzymes. The porphyrin group of chromoproteins is not cleaved.

Of interest is the process of breakdown of nucleoproteins, which are rich in some foods. The nucleic component is separated from the protein in the acidic environment of the stomach. In the intestine, polynucleotides are hydrolyzed by intestinal and pancreatic nucleases.

RNA and DNA are hydrolyzed under the action of pancreatic enzymes - ribonuclease (RNase) and deoxyribonuclease (DNase). Pancreatic RNase has an optimum pH of about 7.5. It cleaves internal internucleotide bonds in RNA. In this case, shorter polynucleotide fragments and cyclic 2,3-nucleotides are formed. Cyclic phosphodiester bonds are hydrolyzed by the same RNase or intestinal phosphodiesterase. Pancreatic DNase hydrolyzes internucleotide bonds in DNA supplied with food.

The products of hydrolysis of polynucleotides - mononucleotides are exposed to the action of enzymes of the intestinal wall: nucleotidase and nucleosidase:

These enzymes have relative group specificity and hydrolyze both ribonucleotides and ribonucleosides and deoxyribonucleotides and deoxyribonucleosides. Nucleosides, nitrogenous bases, ribose or deoxyribose, H 3 PO 4 are absorbed.

I will say this as a doctor who specializes in food hygiene.

Depending on its quantity and composition, food stays in the stomach for 4 to 10 hours (in humans, on average, 3.5-4 hours).
The metabolism of proteins, fats, and carbohydrates in the body is a very complex process.
If you take carbohydrates, then it is necessary to break down to simple monosaccharides, then complex ones begin biochemical reactions- in the liver - conversion of glucose.
Proteins are broken down into amino acids. All this takes time.

So:
Water. When you drink water on an empty stomach, it immediately enters the intestines.
Juices. Fruit juices and vegetable juices and broths are digested in 15-20 minutes.
Semi-liquid products.
Mixed salads, as well as vegetables and fruits, are digested within 20-30 minutes.
Fruits.
Watermelon is digested in 20 minutes. Melons require 30 minutes to digest.
Oranges, grapes and grapefruits also require half an hour to digest.
Apples, pears, peaches, cherries and other semi-sweet fruits are digested in 40 minutes.
Raw vegetables.
Vegetables that go into salads raw - such as tomatoes, lettuce, cucumbers, celery, red or green peppers and other juicy vegetables,
require 30-40 minutes for processing.
If vegetable oil is added to the salad, the time increases to more than an hour.
Vegetables, steamed or boiled in water, greens are digested in 40 minutes.
Zucchini, broccoli, cauliflower, beans,
boiled corn and butter are digested in 45 minutes.
It takes at least 50 minutes for the body to process root vegetables such as turnips, carrots, beets and parsnips.
Vegetables containing starch.
Foods such as Jerusalem artichokes, acorns, pumpkins, sweet and regular potatoes, yams and chestnuts will take about an hour to digest.
Starchy foods.
Hulled rice, buckwheat, millet (it is preferable to use these cereals), corn flour, oatmeal, quinoa, Abyssinian broom, pearl barley are digested on average in 60-90 minutes.
Legumes - starches and proteins.
Lentils, lima and regular beans, chickpeas, cayanus (pigeon peas), etc. require 90 minutes to digest. Soybeans are digested in 120 minutes.
Seeds and nuts.
Sunflower, pumpkin, melon and sesame seeds take about two hours to digest. Nuts such as almonds, hazelnuts, peanuts (raw), cashews, pecans, walnuts and brazil nuts digested in 2.5-3 hours. If seeds and nuts are soaked in water overnight and then crushed, they will be absorbed faster.
Dairy products.
Low-fat homemade cheese, cottage cheese and feta cheese are processed in about 90 minutes. Cottage cheese from whole milk digested in 2 hours.
Whole milk hard cheese, such as Swiss, requires 4-5 hours to digest. Hard cheeses take longer to digest than all other foods due to the large amount of fats and proteins they contain.
Eggs:
30 minutes goes into processing egg yolk, 45 - a whole egg.
Fish:
Fish like regular and small cod, flounder, and halibut fillets can be digested in half an hour. Salmon, trout, tuna, herring (fattier fish) are processed in the stomach within 45-60 minutes.
Chicken (without skin)- in one and a half to two hours.
Turkey (without skin)- two to two hours and fifteen minutes.
Beef and lamb digested within three to four hours.
To be reworked pork, it will take 4.5-5 hours.
Proteins are included in the listed meat products.

For the first time, the idea of ​​​​working on this article arose a long time ago, after reading the “BEFORE and AFTER” posts; “about monosaccharides...”; "about starch..." ...

Then, the table was repeatedly posted on the website about product compatibility

Now here is a post that says: ...." about the emergence of the habit of combining incompatible ingredients in one dish, for example, in the Olivier salad"

But many products AT THE SAME TIME contain proteins, fats, and carbohydrates (see reference books).

Therefore, I decided that it was time to most seriously understand the essence of this “mismatch” and, in general, what is correct, quality nutrition and digestion.

Digestion

The digestion process begins in the mouth. All food products are crushed into smaller particles by chewing, and they are thoroughly saturated with saliva. Concerning chemical side digestion, then only starch digestion. starts in the mouth. Saliva in the mouth, which is usually an alkaline liquid, contains an enzyme called ptyalin, which acts on starch, breaking it down into maltose (a complex sugar), and in the intestines, it is acted upon by the enzyme maltose, converting it into simple sugar (dextrose). The action of ptyalin on starch is preparatory, since maltose cannot act on starch. It is believed that amylase (an enzyme of pancreatic secretion), capable of breaking down starch, acts on starch more powerfully than ptyalin, so that starch that has not been digested in the mouth and stomach can be broken down into maltose and achroodextrin, provided, of course, that it has not undergone fermentation before reaching the intestines.

Digestion of proteins. Stages and sequence of protein digestion

Digestion of proteins in the stomach. Pepsin is an important stomach enzyme that breaks down proteins. Pepsin only begins the process of protein digestion, usually providing only 10-20% of the complete digestion of proteins and their conversion into albumoses, peptones and small polypeptides. This breakdown of proteins occurs as a result of hydrolysis of the peptide bond between amino acids.

Protein digestion occurs predominantly in the upper regions small intestine, in the duodenum and jejunum under the influence of proteolytic enzymes secreted by the pancreas. Partially digested protein food products, entering the small intestine from the stomach, are exposed to the main proteolytic pancreatic enzymes: trypsin, chemotrypsin, carboxypolypeptidase and proelastase.

The final stage of protein digestion in the intestinal lumen is provided by small intestinal enterocytes, which are covered with villi, mainly in the duodenum and jejunum.

More than 99% of the end products of protein digestion that are absorbed are single amino acids. Absorption of peptides occurs very rarely and an entire protein molecule is extremely rarely absorbed. Even an extremely small number of absorbed whole protein molecules can sometimes cause serious allergic or immunological disorders.

Digestion of carbohydrates. The sequence of carbohydrate digestion in the gastrointestinal tract

IN human dietThere are only three main sources of carbohydrates: (1) sucrose, which is a disaccharide and is commonly known as cane sugar; (2) lactose, which is a disaccharide of milk; (3) starch is a polysaccharide present in almost all plant foods, especially in potatoes and various types of grains. Other carbohydrates that are digestible in small quantities are amylose, glycogen, alcohol, lactic acid, pyruvic acid, pectins, dextrins and, in the smallest quantities, derivatives of carbohydrates in meat.

Food also contains large amounts of cellulose, which is a carbohydrate. However, there is no enzyme in the human digestive tract that can break down cellulose, so cellulose is not considered a food product suitable for human consumption.

Digestion of carbohydrates V oral cavity and stomach. When food is chewed, it is mixed with saliva, which contains the digestive enzyme ptyalin (amylase), secreted mainly by the parotid glands. This enzyme hydrolyzes starch into the disaccharide maltose and other small glucose polymers containing 3 to 9 glucose molecules. However, food remains in the oral cavity for a short time, and probably no more than 5% of starch is hydrolyzed before swallowing.

P starch digestion continues in the body and fundus of the stomach for another 1 hour until food begins to mix with gastric secretions. The activity of salivary amylase is then blocked by the hydrochloric acid of gastric secretions. Despite this, on average, up to 30-40% of starch is hydrolyzed into maltose before food and accompanying saliva are completely mixed with gastric secretions.

Digestion of carbohydrates in the small intestine . Digestion by pancreatic amylase. Pancreatic secretion, like saliva, contains a large amount of amylase, but is several times more effective. Thus, no more than 15-30 minutes after the chyme from the stomach enters the duodenum and mixes with pancreatic juice, virtually all carbohydrates are digested.

As a result, before carbohydrates leave the duodenum or upper jejunum, they are almost completely converted to maltose and/or other very small polymers of glucose.

Disaccharides are digested immediately as soon as they come into contact with enterocytes, the protruding villi of the small intestine.

Lactose splits into a galactose molecule and a glucose molecule. Sucrose is broken down into a fructose molecule and a glucose molecule. Maltose and other small glucose polymers are broken down into numerous glucose molecules. Thus, the end products of carbohydrate digestion are monosaccharides. All of them dissolve in water and are instantly absorbed into the portal bloodstream.

In normal food, in which starch is the most abundant of all carbohydrates, more than 80% of the final product of carbohydrate digestion is glucose, and galactose and fructose rarely exceed 10%.

Digestion of fats. Stages of fat digestion in the intestine

Digestion of fats in the intestines . A small amount of triglycerides is digested in the stomach by the action of lingual lipase, which is secreted by the glands of the tongue in the mouth and swallowed along with saliva. The amount of fat digested in this way is less than 10%, and therefore not significant. The main digestion of fats occurs in the small intestine, as discussed below.

Emulsification of fats bile acids and lecithin. The first step in fat digestion is to physically break down the fat droplets into small particles, since water-soluble enzymes can only act on the surface of the droplet. This process is called fat emulsification and begins in the stomach by mixing fats with other products of digestion of gastric contents.

Next is the main stage emulsification occurs in the duodenum under the influence of bile, a liver secretion that does not contain digestive enzymes. However, bile contains a large amount of bile salts, as well as a phospholipid - lecithin. These components, especially lecithin, are extremely important for the emulsification of fats. The polar species (the place where water ionizes) of bile salts and lecithin molecules are highly soluble in water, while most of the remaining molecules are highly soluble in fat.

Thus, fat soluble portions liver secretions dissolve in the surface layer of fat droplets along with the protruding polar part. In turn, the protruding polar part is soluble in the surrounding aqueous phase, which significantly reduces the surface tension of the fats and makes them also soluble.

When surface tension drops of insoluble liquid low, water-insoluble liquid during movement is much more easily broken into many small particles than with a higher surface tension. Therefore, the main function of bile salts and lecithin is to make fat droplets easily crushable when mixed with water in the small intestine. This action is similar to the action of synthetic detergents widely used in households to remove grease.

Relationship between glycemic and insulin indices.

When compiling a nutrition menu, it is very important to understand one more indicator associated with this index. We are talking about the so-called “glycemic load” (GlycemicLoad- G.L.). This indicator allows us to judge the actual level of “glycemic load” when consuming a specific amount of carbohydrates in a serving of a particular dish and in the entire daily diet as a whole.

Let us explain the meaning of the glycemic load index (G.L.) and its calculation with the following example. Let's assume that to prepare a dish (porridge) we want to use 30 g white rice. What will be the actual carbohydrate load of this dish? Following simple arithmetic rules we expect that if glycemic index 100 g of white rice is equal to 70, then the carbohydrate load (G.L.) when using 30 g will be 21 (30x70: 100 = 21). Similarly, the carbohydrate load of any other carbohydrate product is calculated. That is, we multiply the specific carbohydrate content in a serving intended for use by the glycemic index value of this product and divide the result of the multiplication by 100.

Persons with overweight bodies, sick diabetes mellitus as well as some other diseases and conditions that require dietary food while limiting the amount of carbohydrates consumed, you should formulate your daily diet so that its total glycemic index does not exceed 80 - 100.

Here are the comparative values ​​of glycemic and insulin (in parentheses) indices of some food products and products: oatmeal - 60 (40), white flour pasta - 46 (40), white rice - 110 (79), brown rice - 104 (79 ), rye bread - 60 (56), white bread - 100 (100), potatoes - 141 (121), eggs - 42 (31), beef - 21 (51), fish - 28 (59), apples - 50 ( 59), oranges - 39(60), bananas - 79(81), grapes - 74(82), ice cream - 70(89), Mars bars - 79(112), yogurt - 62(115), milk - 30 (90), muesli - 60 (40), corn flakes - 76 (75).

From the above data it is clear that although between insulin and glycemic e In most cases, according to the Chinese indices of food products, there is a proportional relationship (higher the glycemic index, higher the insulin index, and vice versa); such a dependence is not obligatory for all products. It has been found that foods rich in protein and carbohydrates containing fat have an insulin index (response) that is disproportionately higher than the glycemic index of these foods.

Interpretation of such a response is difficult. On the one hand, the positive thing is that increasing insulin levels contributes to more low level postprandial glycemia. However, the negative is that to achieve such an effect, the body will contribute to the depletion of beta cells of the pancreas and the development of type 2 diabetes.

The disproportionate increase in AI has its own explanations. According to S. Holt and her co-authors, this is due to the fact that insulin helps digest food not only in terms of carbohydrate absorption. It is needed for amino acids in muscle cells involved in the process of carbohydrate absorption. Increased insulin It is also necessary because when consuming protein foods, glucagon is released from the liver, which increases blood sugar levels. For healthy people this is not a problem. The picture is different in diabetes, when the physiological mechanism compensation and it is much more difficult for the body to compensate for glycemia, because he is also forced to cope with an additional carbohydrate load caused by the release of glucagon from the liver under the influence of protein products

According to the level of AI, food products are divided into three groups.

First. Having high AI. These include bread, milk, yogurt, confectionery, potatoes, breakfast cereals

Second. Products with a moderately high (average) level of I.I. - beef, fish

Third. Low AI products. - eggs, buckwheat, oatmeal, muesli.

From the above, an important conclusion for nutrition follows:

When consuming certain low-glycemic index protein foods (such as beef), insulin release may be disproportionately higher to achieve a relatively low glycemic level than when consuming most carbohydrate foods.

It is necessary to take into account not only the content of carbohydrates in food, but their energy value. With the same carbohydrate content, energy value products due to proteins and fats is higher and this in turn determines the need for higher insulinemia.

It follows from this that only the glycemic index of foods does not always characterize the need for insulin necessary for their absorption and the load on its secretion by the beta cells of the pancreas. This observation is very important practical significance, because allows you to more correctly regulate insulin therapy for diabetes.
Additionally, equal portions of carbohydrate foods do not necessarily stimulate insulin secretion to the same extent. For example, the isoenergetic servings of pasta and potatoes both contained ~50g carbohydrates, but the IS for potatoes was three times greater than for pasta.

In dietetics, the following scale of glycemic load levels of individual portions (meals, dishes) of food is accepted: low is consideredG.L.up to 10, medium - from 11 to 19, high - more than 20.

Knowing what the GI of the original products is and the glycemic load index of the actual diet, you can evaluate and adjust the overall level and tolerance of the glycemic load per day. The usual total daily food load on the glycemic index varies widely, on average between 60 and 180. The level of total glycemic load is considered low (G.L.) not exceeding 80, average - from 81 to 119, high - 120 or more.

Reactive hypoglycemia occurs when simultaneous use large amounts of carbohydrates. The increased level of insulin signals the liver to simultaneously receive a large amount of sugar. To protect the brain (excess glucose is dangerous for it), the liver begins to convert sugar into fat. The supply of sugar decreases, and the brain, not receiving enough energy, sends a signal to the adrenal glands, demanding increased production of adrenaline. Under the influence of adrenaline, sugar reserves from the liver enter the bloodstream to maintain a constant supply of sugar to the brain. At this time, the brain begins to demand that you eat something else containing carbohydrates. After you obey the brain's demand, insulin levels rise, the liver again converts almost all of the incoming sugar into fat - the circle is closed.

Carbohydrates, insulin and glucagon

Carbohydrates are sugar

Carbohydrates are divided into simple and complex. Simple carbohydrate molecules consist of one or two sugar molecules, complex carbohydrate molecules are a chain of three or more sugar molecules connected to each other. Carbohydrates are found in many foods, real and artificial: cereals and cereals, starchy vegetables, fruits, most dairy products, bread, pasta and sweets. In the digestive tract, simple (fruits, candies) and complex (vegetables, cereals) carbohydrates are broken down into single sugar molecules (monosaccharides). Therefore, all carbohydrates are sugar.

Insulin and glucagon

The body's ability to use carbohydrates from food depends on the ratio of insulin and glucagon levels, the two main pancreatic hormones that regulate the distribution of nutrients in the body.

Glucagon is a hormone that causes the liver to release sugar (glucose), which increases the level of glucose in the blood that enters the brain and body cells. In addition, glucagon causes cells to release fat (to be used as energy) and proteins (to be used as building materials).

If glucagon is responsible for the use of nutrients, then insulin is responsible for their storage. Under the influence of insulin, sugar, fat and proteins are sent from the bloodstream into the cells. The process of migration of nutrients from the blood into cells is vital important for two reasons. Firstly, while the cells receive the energy and building materials necessary for their life and renewal, and the blood sugar level is maintained in a balanced state, which protects the brain from dangerous changes in sugar concentration. Secondly, insulin tells the liver that excess sugar has entered the body, and the liver begins to convert the excess sugar into fat.

From the ratio of insulin and glucagon levels depends on whether the food we eat will be used by the body to obtain energy and building materials , or it will turn into fat reserves.

With a low ratio of insulin and glucagon levels (i.e., when glucagon levels are relatively high) the bulk of the meal converted into energy and building materials

with a high insulin/gayukagon ratio(i.e., with relatively high insulin levels) - into fat.

The pancreas begins to produce glucagon when proteins enter the body.

The production of insulin is caused by carbohydrates, as well as some amino acids.

When non-starchy vegetables (fiber) and fats enter the body, neither insulin nor glucagon is produced.

Hence, if the food consists only of carbohydrates, That ratio of insulin and glucagon levels will become too high.

If the food consists of only proteins, then this ratio will be too low.

If the meal consists of only non-starchy vegetables or fats, the insulin/glucagon ratio will remain the same as before the meal.

If the food contains proteins, fats, non-starchy vegetables and carbohydrates, then the insulin/glucagon ratio will be maintained in balance.

Achieving and maintaining a balance of insulin and glucagon in the body is the goal of a balanced diet.

1 When you eat refined carbohydrates (processed carbohydrates, e.g. White bread): Refined carbohydrates are quickly digested in the intestines, turning into sugar. Sugar immediately enters the portal vein, causing a sharp rise in insulin levels.

2 When you eat complex carbohydrates (for example, whole wheat bread): complex carbohydrates are digested more slowly, so the sugar does not enter the portal vein immediately, but gradually. This does not happen sharp jump blood sugar levels, so there is no sharp increase in insulin production, but the insulin level still exceeds the equilibrium value.

3 When you eat nutritionally balanced foods (such as chicken, broccoli, and baked potatoes with butter): When food contains proteins, fats, carbohydrates and non-starchy vegetables (fiber) in balanced quantities, digestion occurs even more slowly than when consuming complex carbohydrates. As a result, insulin levels are maintained within normal limits throughout long period time.

The ratio of insulin and glucagon levels, in addition to the factors mentioned, depends on the glycemic index of foods. The glycemic index of foods is an indicator that characterizes the rate of conversion of food carbohydrates into blood glucose, and therefore the rate of increase in insulin levels after consuming this product. The faster the glucose level in the portal vein blood rises, the higher the glycemic index of a given product. Typically, the glycemic index of simple sugars is higher than complex sugars. This means that after consuming simple sugars, your blood glucose levels rise faster.

Whole grain cereals and flours have a lower glycemic index than refined flours and polished cereals. Whole grain cereals and flour contain bran, i.e. fiber, which slows down the absorption of sugar into the blood, which reduces the ratio of insulin and glucagon levels. Fiber, which protects the body from sudden changes in sugar levels, has been removed from refined flour and polished cereals (in particular, white rice), and the glycemic index of these products is higher.

Why should nutrition be balanced?

It is extremely important that you have on your table all four nutrient groups at once(proteins, fats, carbohydrates, fiber). If your lunch consists of just potatoes, then the overall glycemic index of that lunch will be quite high. If you add fish, stewed cabbage and salad to potatoes fresh vegetables, then the overall glycemic index of your lunch will be lower than in the first case, since carbohydrates are digested and absorbed into the blood much faster than proteins and fats. Carbohydrates cause insulin secretion but do not increase glucagon levels.

With an excess of carbohydrates in the diet or when consuming carbohydrates alone without fats and proteins, insulin secretion increases, and glucagon secretion decreases (i.e., the insulin/glucagon ratio increases). Consequently, excess carbohydrates will mainly be stored in your body as fat reserves.

If you eat carbohydrates and proteins at the same time, the pancreas secretes both insulin and glucagon (the ratio of insulin to glucagon levels is less than in the first case). As a result, your lunch will not turn into fat, but will be used as a source of energy or building material for renewing body cells.

Contrary to obvious facts, people continue to believe that protein and fat make you fat. In fact, proteins and fats, by helping to maintain the balance of insulin and glucagon, prevent the formation of fatty deposits.

On the contrary, carbohydrates, by increasing the insulin/glucagon ratio, promote the formation and deposition of fat in the body.

Another common misconception is that carbohydrates make you feel full quickly. But this belief is also wrong. When you eat carbohydrates, you only feel full when you've already eaten more than you should!

The body provides " defense mechanism”, preventing the consumption of excess amounts of proteins and fats. However, the body has no protection against consuming excess carbohydrates.

Real hunger (as opposed to pseudo-hunger caused by a lack of serotonin in the brain) occurs when the brain begins to receive fewer nutrients. The brain sends the body a message: “Feed me quickly, I don’t have enough energy.”

When you eat a meal containing proteins and fats, it is digested in the stomach, where proteins are broken down into amino acids by gastric juice and digestive enzymes. The stomach sends electrical signals to the brain, informing the body that nutrients are entering the body, and the feeling of hunger subsides.

From the stomach, proteins and fats enter the small intestine. Cells in the intestinal wall secrete the hormone cholecystokinin (CCK). When CCK enters the brain in the blood, it signals that food is already being digested. Under the influence of CCK gallbladder begins to contract, releasing bile into the intestines, which is necessary for complete digestion and absorption of fats. With an excess of CCK, nausea occurs. If you ignore this signal and continue to eat, your nausea will worsen and you will eventually vomit.

Many people claim that eating carbohydrates causes pleasant feeling lightness in the stomach. The fact is that carbohydrates bypass the stomach without staying in it and go straight to the small intestine.

There is no irritation of the stomach walls, no release of CCK, signaling the brain about satiety.

And only when sugar is absorbed into the blood and causes the release of insulin, which in turn stimulates a temporary increase in serotonin levels in the brain, the feeling of hunger will begin to subside. Complete saturation occurs only after blood saturated with glucose enters the brain from the liver. This whole process takes quite long time, enough to empty an entire box of cereal.

Unlike carbohydrates -bTrees and fats, long before the end of their digestion, send signals to the brain: “That’s enough, don’t ask for more.”

People often say: “I feel hungry all the time. I eat, eat, eat and just can’t get enough.” But it almost always turns out that these people absorb in huge quantities not proteins and fats, but carbohydrates. For those who can’t decide to accept the “right to nutritious food,” I suggest doing an experiment: changing your diet for just one week. For breakfast, there are eggs (as much as you want) with vegetables and “country” sausage without nitrates, as well as one sandwich of whole grain bread with butter. For lunch - vegetable salad with chicken and fruit. For dinner - a portion of fish, chicken or red meat with stewed vegetables, a salad of fresh vegetables with vinegar and olive oil, as well as one baked potato, generously sprinkled with sour cream or butter.

In case you want to eat between meals, you should have a snack ready that contains proteins, fats and carbohydrates (for example, nuts or cream cheese plus some fruit).

To successfully change your diet and lifestyle, it is very important to prevent serotonin deficiency in the brain. Remember that healing requires time, patience and rebalancing serotonin, and this cannot happen overnight.

However, with patience and perseverance, you will be rewarded. One of the pleasant surprises for you will be the restoration of your ideal body composition and the loss of excess fat.

Conclusions:

1. The main process of food digestion occurs not in the stomach, but in a special section of the intestine - the duodenum and small intestine, in which enzymes for breaking down food act simultaneously

2. Duodenum, small intestine in which enzymes simultaneously and perfectly digest proteins (trypsin), fats (lipase), and carbohydrates (amylase) - which is another thing proves the unnaturalness and inconsistency of the concept of “separate” nutrition.

Based on materials from the site: zazdorovie.ru -Swedish biochemist, doctor, nutritionist Diana Schwartzbein.

asked by the author LILITH DANIELYAN, the best answer is: Of all the substances that come with food, mainly only proteins are digested in the stomach. However, all fats, except milk fat, are not in an emulsion state. There are no conditions for the emulsification of fats in the stomach; therefore, only those fats that come in an emulsified state can be digested in it. In addition to milk fat, the fats that make up mayonnaise are also in an emulsified state. Thanks to this, the fats in mayonnaise can be digested in the stomach. Gastric juice does not contain enzymes capable of digesting carbohydrates (starch). Therefore, they would have to remain unchanged in the stomach. But the food gruel entering the stomach is usually richly saturated with saliva, which contains the enzyme ptyalin, which breaks down starch. After entering the stomach, this enzyme continues to digest starch for some time. Its effect stops as soon as gastric juice begins to penetrate deep into the food bolus.

hydrocarbon?? ? in the stomach. however.

A hydrocarbon is both protein and fat and ethyl alcohol, you meant carbohydrates!

Digestion of carbohydrates (not hydrocarbons) already begins in the oral cavity under the action of salivary enzymes.

proteins, fats and carbohydrates are digested in the gastrointestinal tract (gastrointestinal tract)

Proteins and carbohydrates in the stomach are incompatible

The function of the stomach is the digestion and fermentation of chewed food in gastric juice, i.e. in an acidic environment. The stomach reflexively secretes juice and enzymes before eating, and we experience a feeling of hunger, sometimes painfully piercing: the walls of the stomach are sensitive even to its own acidity. The stomach, however, does not secrete more juice than is necessary to digest food. Ideally, digestion lasts no more than two hours, then the food gruel passes into the intestines, and in its alkaline environment fermentation and absorption of digested proteins and fats continues.

Mostly protein foods (meat, cheese, eggs) dissolve and ferment in gastric juice. What happens in the stomach with undissolved carbohydrates - potatoes, bread, noodles, rice, buckwheat porridge - while the meat is being digested? Of course, the combination of sweet and sour at a temperature of about 37 ° C will lead to fermentation and gases. Elementary chemistry. Gases tend to escape from the stomach at the first opportunity (belching). At the moment when the esophageal sphincter relaxes, gastric juice rises up along with gases and causes a burning sensation. Elementary physics.

Heartburn (gastroesophageal reflux disease, GERD, heartburn) comes from the word to burn, which is what hydrochloric acid does to those places that do not expect contact with it. More than 60 million Americans suffer from heartburn at least once a month. Chronic heartburn is accompanied by inflammation and scarring of the walls and, as a result, narrowing of the esophagus, and this can lead to Barrett disease, which significantly increases the risk of esophageal cancer. Those suffering from Barrett's disease have a smell of stomach contents from their breath due to a constantly open valve. At this stage, intervention by a gastroenterologist, possibly surgical, is already necessary.

As you can see, heartburn is just the tip of the iceberg of a mixed diet. When fermenting carbohydrate foods, saturated with hydrochloric acid (pH = 1-1.5), finally enter the intestines (pH = 8.9), miracles happen there too - from duodenal ulcers to nonspecific colitis. What mucous membrane and what symbiotic bacteria will withstand regular chemical attack with hydrochloric acid!

A holy place is never empty - yeast bacteria love a warm, acidic environment. However, what is appropriate for rising yeast dough is inappropriate for your body: gas, bloating and yeast infections are too high a price to pay for the momentary pleasure of meat, fried potatoes and bread.

Don't be afraid to eat meat, poultry or fish an hour or two before bed, because, unlike vegetables and fruits, meat is quickly digested, neutralizes gastric juice, lowers blood pressure and contains amino acids that promote good sleep and rest. If you still cannot deny yourself fruits and berries, reserve them for the morning. Firstly, they will slip into the intestines without fermentation and hydrochloric acid, secondly, during the day you will have time to use up excess glucose and not store it in fat, thirdly, they will not interfere with the digestion of proteins and fats and, fourth, without excess sugar and, accordingly, insulin in the blood, you will have deeper and more restful sleep. Remember, for complete digestion and absorption of protein foods, it takes two to three hours, carbohydrates - from five to six, and fiber, especially dense fiber - even more.

WHAT IS DIGESTED IN THE STOMACH: protein, fat or hydrocarbon? PLEZZZZZZZZZZZ I REALLY NEED IT!

So, fats are not digested in the stomach and proteins are partially digested, fats are digested in the intestines, and proteins in the stomach only undergo fermentation, the main absorption occurs after the stomach, carbohydrates are digested mainly in the stomach.

Everything else, proteins, fats and carbohydrates are digested in the gastrointestinal tract (gastrointestinal tract)

For details, I advise you to go to Wikipedia

The nutrition of a modern person “beats” in time with the active rhythm of life. Some “swallow on the go” because there is no time to stop in the bustling flow and enjoy the meal. Others, avid athletes, perceive food only as a source of muscle growth. Still others – everyone and everything (problems, stress) eat “sweets”. We won’t examine whether this is correct, but let’s turn to this question. Who has ever wondered what happens to food after it enters the stomach? We believe that there are only a few. But how food is digested depends correct work Gastrointestinal tract and human health in general. Let's try to figure out these questions. We will also find out how long food takes to digest, which is absorbed faster, which is slower (tables) and much more.

Few of you know that the process of digestion and assimilation of food directly affects good health person. Knowing how our body works, we can easily adjust our diet and make it balanced. The functioning of the entire digestive system depends on how long food is digested. If the gastrointestinal tract functions correctly, then metabolism is not disturbed, there are no problems with overweight and the body is completely healthy.

How does metabolism work?

Let's start with the concept of “digestion of food”. This is a combination of biochemical and mechanical processes, as a result of which food is crushed and broken down into nutrients useful to the body (minerals, vitamins, macro- and microelements).

From the mouth, food enters the stomach, where it becomes liquid under the influence of gastric juice. This process lasts 1-6 hours (depending on the product eaten). Next, the meal moves to the duodenum (the beginning of the small intestine). Here, food is broken down into essential nutrients by enzymes. Proteins are converted into amino acids, fats into fatty acids and monoglycerides, carbohydrates into glucose. Absorbed through the intestinal walls, the resulting substances enter the bloodstream and are distributed throughout the human body.

Digestion and absorption are complex processes that take hours. It is important for a person to know and take into account the factors influencing the speed of these reactions.

How long does it take for food to be digested? What determines the duration of this process?

• From the method of processing the products entering the stomach, the presence of fat, spices, and so on.
• How long the stomach takes to digest food depends on its temperature. The rate of absorption of cold is much lower than hot. But both temperatures of the food bolus interfere with normal digestion. Cold food enters the lower levels of the gastrointestinal tract ahead of time, taking with it lumps of undigested food. A dish that is too hot burns the esophageal mucosa. Optimal temperature for our stomach - warm food.
• From the compatibility of consumed food products. For example, meat, fish and eggs are protein snacks that take different times to digest. If you eat them at one time, your stomach will be at a loss, not knowing which protein to digest first. The egg is digested faster and along with it an underdigested piece of meat can slip into the small intestine. This can lead to fermentation and even rotting processes.

Based on the speed of absorption and compatibility, there are three main categories of food:

1. The first group has the same digestion time. These products are used in fresh, not thermally processed, without fats and sugar. How long does it take for such food to be digested – up to 45 minutes.
2. The second group is protein products with the same digestion time, with fats, sugar or spices. Adding the latter increases the digestion time to 2 hours.
3. The third group is complex carbohydrates and proteins with fats. They take up to 3 hours to digest.
4. The fourth group is food that takes more than 3 hours to digest. Some of it is not digested at all and is excreted from the body.

How and where are carbohydrates digested?

The breakdown of carbohydrates is carried out under the action of an enzyme such as amylase. The latter is contained in the salivary and pancreas glands. Therefore, carbohydrate foods begin to be digested in the oral cavity. It is not digested in the stomach. Gastric juice has an acidic environment, which inhibits the action of amylase, which requires an alkaline pH. Where are carbohydrates processed - in the duodenum. Here they are finally digested. Under the action of a pancreatic enzyme, glycogen is converted into nutrient disaccharides. In the small intestine they are converted to glucose, galactose or fructose.

There are two types of carbohydrates: simple (fast) and complex (slow). How long they take to digest depends on their type. Complex substances are digested more slowly and absorbed at the same speed. For how long they stay in the digestive tract, see the tables above.

How long does it take to digest fast (simple) carbohydrates (table)? By the way, this group of nutrients contributes to an almost immediate increase in blood sugar levels.

How and where are fats digested?

Dislike for fats is traditional and supported by many nutritionists. What is this connected with? – With their high calorie content. There are as many as 9 kcal per 1 gram. However, fats are important in the human diet. They are the body's most valuable source of energy. The absorption of vitamins A, D, E and others depends on their presence in the diet. In addition, foods rich in healthy fats have a beneficial effect on the entire digestive process. These products include meat and fish, olive oil, and nuts. But there are also bad fats - fried foods, fast food, confectionery.

How and where are fats digested in the human body? – In the mouth, such food does not undergo any changes, since there are no enzymes in saliva that can break down fats. The stomach also does not have the necessary conditions for digesting these substances. What remains are the upper parts of the small intestine, that is, the duodenum.

How and where are proteins digested?

Squirrels are another one important element nutrition of every person. They are recommended to be consumed for breakfast and lunch along with foods rich in fiber.

How long it takes to digest proteins depends on the following factors:

• The origin of proteins is animal and plant (see table above).
• Compound. It is known that proteins have a certain set of amino acids. A deficiency in one may interfere with the proper absorption of others.

Proteins begin to be digested in the stomach. Pepsin is present in gastric juice, which can cope with this challenging task. Further splitting continues in the duodenum and ends in the small intestine. In some cases, the final point of digestion is the large intestine.

Instead of a conclusion

Now we know how long it takes for food to be digested in the human body.

What else is important to know:

• If you drink a glass of water on an empty stomach, the liquid goes straight into the intestines.
• You should not drink drinks after meals. The liquid dilutes the gastric juice, which prevents it from being digested. This way, undigested foods can enter the intestines along with water. The latter causes fermentation and even rotting processes.
• To increase the rate of absorption of food, it should be chewed more thoroughly in the mouth.
• In the evening, it is recommended to consume foods from groups 1 and 2 (see table above).
• It is better not to eat food with at different times digestion in the stomach.
• Products of the fourth category should be present in a minimum amount in the diet.
• To make seeds and nuts digest faster, it is recommended to crush them and soak them in water overnight.

DIGESTION IN THE STOMACH

Food stays in the stomach from 2 to 10 hours. This time depends on its qualitative composition, volume, consistency, active reaction and, ultimately, on the osmotic pressure of the chyme. In the stomach, first of all, the liquefaction of the food bolus occurs under the influence of the secreted gastric juice, the amount of which reaches approximately 3 liters per day. Pendulum-like contractions of the muscles of the gastric walls contribute to further grinding of food. As a result, chyme is formed, which, under the influence of peristaltic contractions, enters the duodenum in portions. Chyme provides an aqueous phase - enzymes only work in a liquid medium - and its consistency makes it easier for enzymes to reach food particles.

Hydrolysis of proteins, fats and carbohydrates in the stomach

Cavitary digestion predominates in the stomach. Enzymatic hydrolysis of proteins plays a leading role in the stomach's digestive function.

Proteins, under the influence of hydrochloric acid in gastric juice, swell and loosen, which makes them more accessible to enzymes. Gastric juice, thanks to the enzymes it contains - pepsin, gastricsin, pepsin B, has very high proteolytic activity. Under the influence of gastric juice, a rough breakdown of protein molecules occurs. The products of protein hydrolysis in the stomach are still quite large in size and therefore are not absorbed in the stomach. Some proteases of gastric juice are secreted in an inactive form and are activated by hydrochloric acid, which is part of its composition.

Carbohydrates in the stomach are digested within a short time - approximately 40 minutes and only under the influence of carbonic anhydrases (amylase and maltase) in saliva. Saliva enzymes work in an alkaline environment. As the acidic gastric juice (containing hydrochloric acid) permeates the bolus, their effect ceases. Gastric juice does not contain carbonic anhydrases, and therefore further digestion of carbohydrates will occur only in the intestine. Fats are also hardly digested in the stomach. Gastric juice contains lipase, an enzyme that hydrolyzes fats. But the optimal action of gastric lipase is determined by pH = 5, which does not coincide with the active reaction of gastric juice, the pH of which during the digestion process is sharply acidic (pH = 0.1) in nature. The target of low-active gastric lipase is mainly emulsified milk fats.

Regulation of gastric juice secretion

The secretion of gastric juice occurs in 3 phases - complex reflex, neurohumoral and intestinal.

The complex reflex phase has a complex nature and determines the secretion of the gastric glands under the influence of unconditional and conditioned reflex influences. Unconditional reflex secretion begins with receptors in the oral cavity; From the “distant” receptors of the eye, hearing and smell receptors, the secretion of the stomach glands is triggered by a conditioned reflex. Usually, gastric juice begins to be released after 2-3 minutes at the sight of food, its smell, the sound of dishes, etc. This is a conditioned reflex secretion, which is then supported by irritation of the receptors in the oral cavity when food enters there, i.e. activation of the unconditional reflex mechanism. Secretion of the digestive glands of the stomach begins in the absence of direct contact of food with its receptors. This is an unconditional reflex mechanism for triggering gastric juice secretion.

The neurohumoral phase of secretion from the gastric glands (gastric phase) begins when food enters the stomach. During this phase, the secretion of the gastric glands is due to unconditional reflex stimulation and the influence humoral factors. Unconditional reflex stimulation of gastric secretion occurs when the stomach receptors are excited by a bolus of food. Then secretion is activated under the influence of humoral substances, both those included in the food itself or the products of its digestion, and specific digestive hormones. Gastrin, which is formed in the mucous membrane of the pyloric part of the stomach, stimulates the functioning of its glands. During the digestion process, the secretion of the gastric glands gradually decreases, which occurs under the influence of two other hormones: gastrogastron and enterogastron. The first is formed in the mucous membrane of the pyloric part of the stomach, the second - in the mucous membrane of the upper part of the small intestine. Enterogastron is formed under the influence of food fat, its digestion products and hydrochloric acid.

The motor activity of the stomach ensures mixing of the food mass and evacuation of the contents from the stomach. At first after eating, the motor activity of the stomach is weakened, but as the food mass becomes saturated with gastric juice, it begins to intensify and is expressed in periodically occurring and following one after another peristaltic waves, which later increasingly end with the opening of the pyloric sphincter. As a result, small portions of the stomach contents pass into the intestines. The opening of the sphincter is also facilitated by irritation of the sphincter area from the stomach, while irritation of the same acidic contents of the sphincter from the intestine causes immediate closure of the sphincter, and it remains in this state until the food mass that has entered the intestine is completely neutralized.

When using editorial materials in full or in part, an active, indexed hyperlink to km.ru is required!

If you would like to give us advice on how to improve the site, you can do so here. Hosting provided by e-Style Telecom.

Proteins, fats and carbohydrates are digested in the stomach

in English language.

in mathematics and Russian

Choose the correct statement.

1) protein digestion does not occur in the stomach

2) proteins, fats and carbohydrates are digested in the stomach

3) fats, carbohydrates and nucleic acids are digested in the stomach

4) only proteins are digested in the stomach

Main digestive function stomach - protein digestion. Gastric juice does not contain enzymes capable of digesting carbohydrates (starch).

The correct answer is listed at number 4.

“Pepsin “cuts” large protein molecules into individual fragments and amino acids. Lipase breaks down the jury into glycerol and fatty acids.”

Biology. Man and his health. 8th grade Rokhlov. 2007.

Based on this, proteins and fats are broken down in the stomach. And not “only proteins” as stated in the correct answer. Is not it?

Of course, you can solve it by elimination, but still.

in the stomach they break down:

1. under the action of the enzyme pepsin, proteins are formed into polypeptides

2. under the action of the lipase enzyme, fats are broken down into glycerol and fatty carboxylic acids

68.Digestion of proteins, fats and carbohydrates in the digestive tract.

present in plant foods mainly in the form of starch. During digestion, it is converted into glucose, which can be stored in the form of a polymer - glycogen - and used by the body. The starch molecule is a very large polymer formed by many glucose molecules. In its raw form, starch is enclosed in granules that must be broken down before it can be converted into glucose. Processing and cooking lead to the destruction of some of the starch granules.

Some foods contain carbohydrates in the form of disaccharides. These relatively simple sugars, particularly sucrose (cane sugar) and lactose ( milk sugar), during the digestion process they turn into even simpler compounds - monosaccharides. The latter do not need to be digested.

They are polymers of different compositions, the formation of which involves 20 types of amino acids. When proteins are digested, free amino acids and ammonia are formed as end products. Important intermediate digestion products are albumoses, peptones, polypeptides and dipeptides.

Dietary fats are mainly represented by neutral fats, or triglycerides. These are relatively simple compounds that, during digestion, break down into their component parts - glycerol and fatty acids.

69.Functions of the large intestine. Microflora of the large intestine. Protective function of the large intestine.

Functions of the large intestine:

1. Formation of feces occurs in it.

2.Excretory function. Undigested residues, mainly fiber, are excreted through the large intestine. In addition, urea is released through it, uric acid, creatinine. If undigested fats are ingested, they are excreted in the feces (steatorrhoea).

3.Final digestion. It occurs under the influence of enzymes coming from the small intestine, as well as enzymes from the large intestine.

4. Synthesis of vitamins. The intestinal microflora synthesizes vitamins B6, B12, K, E.

5.Protective function. Obligate intestinal microflora suppresses the development of pathogenic microflora. The acidic products it secretes inhibit the processes of decay. She also stimulates nonspecific immunity body.

The role of the microflora of the large intestine. The human large intestine, unlike other parts of the digestive tract, is abundantly populated with microorganisms. More than 400-500 different types of bacteria live here. According to scientists, in 1 gram of feces there are on average billions of them. About 90% of the colon microflora is obligate anaerobic bifidobacteria And bacteroides. Lactic acid bacteria, E. coli, and streptococci are found in smaller quantities. Microorganisms of the large intestine perform a number of important functions. Enzymes produced by bacteria can partially break down plant fibers - cellulose, pectins, lignins - that are undigested in the upper parts of the digestive tract. Microflora of the large intestine synthesizes vitamins K And Group B(B[, Bg, B12), which can be absorbed in small quantities in the large intestine. Disturbance of the normal composition of the microflora of the large intestine with long-term use antibacterial drugs is accompanied by the active proliferation of pathogenic microbes and leads to a decrease in immune defense body.

To continue downloading, you need to collect the image:

Digestion in the gastrointestinal tract

IN gastrointestinal tract food is digested and absorbed. Digestive glands in various sections secrete various juices, containing acid or alkali and various enzymes adapted to the quality of the food. Enzymes break down complex chemicals - proteins, fats, carbohydrates - into simple soluble compounds.

Digestion begins in the oral cavity, where with the help of the masticatory apparatus - jaws and teeth - food is crushed, and starch is broken down by the enzyme ptyalin contained in saliva. Food moistened with saliva is easier to swallow; dry food produces more saliva than liquid food.

The secretory function of the stomach - the separation of gastric juice - is carried out by glands located in the mucous membrane.

The great Russian physiologist I.P. Pavlov and his students showed the enormous influence of the central nervous system on the digestive processes. According to the teachings of I.P. Pavlova, the secretion of gastric juice begins before eating. Sensory irritation attractive looking and the smell of food, table setting, as well as the corresponding pleasant environment through nervous system transmitted to the glands of the stomach, which secrete abundant “appetizing” juice. If the timing of meals is observed, a time reflex is developed, and at certain hours the food center becomes excited, appetite appears and the secretion of gastric juice begins. This first phase of secretion is called conditioned reflex or mental.

Gastric juice has a sharply acidic reaction due to the content of hydrochloric acid. Only in the pyloric part is the juice of the alkaline reaction secreted. Gastric juice contains the enzyme pepsin, which breaks down proteins into simpler compounds. The action of pepsin occurs only in an acidic environment.

Hydrochloric acid plays an important role in digestion:

1. It promotes swelling and loosening of food proteins, preparing them for further enzymatic digestion; The effect of hydrochloric acid on the connective tissue of meat and vegetable fiber; with a lack of hydrochloric acid in the gastric juice, the digestion of meat containing coarse connective tissue fibers is impaired, and plant products, rich in fiber - vegetables, fruits, berries, flour bread coarse, legumes.

2. During gastric digestion, hydrochloric acid causes the pylorus to close, thus preventing undigested food from entering the intestines.

3. Stimulates the secretion of juice by the pancreas.

4. Possesses bactericidal effect- under its influence, microbes that enter the stomach with food die.

Food introduced into the stomach affects the secretion of gastric juice. This second phase of secretion is called chemical. There are weak and strong pathogens of gastric secretion; they are chemical irritants.

Weak stimulants of gastric juice secretion include drinking water, alkaline waters that do not contain carbon dioxide, fat milk, cream, whipped or boiled liquid protein, boiled and pureed meat, boiled fish, vegetable puree, pureed vegetable soups based on weak vegetable broth that do not contain cabbage. , slimy cereal soups and well-cooked porridges.

TO strong pathogens secretions include:

1. meat, fish, chicken broths, as well as mushroom and strong vegetable broths;
2. salty foods;
3. products containing acid;
4. spices - mustard, pepper, cinnamon, cloves;
5. all drinks containing carbon dioxide;
6. canned meat and fish, as well as smoked products;
7. all fried foods;
8. vegetables stewed in their own juice;
9. strong tea and black coffee.

Food substances that stimulate gastric secretion are excluded from the diet of patients with high acidity of gastric juice. And for patients with insufficient secretory function of the stomach, foods and dishes are introduced into the food that stimulate the secretion of gastric juice, but do not irritate the gastric mucosa.

Each meal, depending on its nature, is a greater or lesser load for gastric digestion and is regarded as a mechanical irritant. Therefore, in case of diseases of the stomach, when it is necessary to spare the diseased organ, foods and dishes that take a long time to be digested in it are excluded from food.

The time during which food is retained and digested in the stomach depends primarily on its consistency:

1) dense food is digested slowly in the stomach until it turns into liquid gruel;

2) pureed and mushy food begins to pass into the intestines in separate portions within a few minutes after eating;

3) liquids can pass into the intestine without any changes in the stomach, and heated liquids pass faster than cold ones.

The motor function of the stomach is that the muscles of the stomach wall, periodically contracting, mix and move food to the exit; at this time, the pylorus opens and passes individual portions into the duodenum, where the bile duct and pancreatic duct open.

The pancreas - one of the most important digestive glands - secretes juice containing highly active enzymes: trypsin, which completes the digestion of proteins into amino acids; lipase, which breaks down fats into glycerol and fatty acids; and amylase, which breaks down starch and sugars into glucose. Along with pancreatic juice, bile enters the duodenum, the presence of which is necessary for the breakdown and absorption of fats.

IN small intestines Nutrients and part of the water are absorbed into the blood. In the large intestines, water absorption ends and feces are formed.

In the walls of the small and large intestines there are muscle fibers, which, constantly contracting and relaxing, mix and move the food mass through the intestines. Intestinal contents are a natural irritant to intestinal peristalsis. Based on their effect on intestinal function, nutrients can be divided into three groups:

1) enhancing peristalsis and promoting bowel movement;

2) delaying peristalsis;

3) indifferent substances.

Substances that enhance intestinal motility include:

1. sugary substances - honey, jam, sweet syrups, sweet fruits, fruit sugar, milk sugar;
2. products containing organic acids - sour dairy products, kvass and other sour drinks, sour fruits, sour black bread;
3. foods rich in table salt;
4. drinks containing carbon dioxide;
5. fats, especially vegetable oil in a free state in vinaigrettes, salads;
6. foods rich in coarse plant fiber and causing mechanical irritation (vegetables, fruits, berries, Rye bread and wheat from wholemeal flour, buckwheat, pearl barley, millet porridge);
7. cold drinks, cold soups (fruit, okroshka) provided they are taken on an “empty” stomach (thermal factor).

TO nutrients, braking intestinal peristalsis, relate:

1. products containing tannins, having astringent action(decoction of blueberries and pears, red wine, acorn coffee, strong tea);
2. food devoid of chemical and mechanical irritants to the intestines (rice water, starch);
3. hot drinks (temperature factor).

Indifferent substances are meat, fish, white bread, semolina and rice porridge.

A healthy person with a varied diet receives enough stimuli to support timely bowel movements. Poor nutrition, exclusion of vegetables, fruits, black bread and others from food similar products may cause nutritional constipation. That is why, with these constipations, as well as with constipation of other origins, it is necessary to include substances that enhance peristalsis in the diet.

In conditions normal digestion In the small intestines, microflora is usually absent. The large intestines constantly contain a large number of microbes that break down plant fiber and the remains of protein products. Moreover, normal intestinal microflora performs the following functions:

a) protects against foreign microbes;

b) synthesizes some B vitamins, folic acid, vitamin K.

Proper organization therapeutic nutrition is of great importance in the treatment of chronic diseases of the digestive system and the prevention of exacerbations. At acute diseases Diet therapy can prevent them from becoming chronic.

Diet therapy is carried out depending on the stage of the disease. In the acute period or during an exacerbation, a diet that is most gentle to the diseased organ is indicated. As the patient's condition improves, the diet is gradually expanded with the introduction of coarser foods. Such training of the digestive organs with coarser products is acceptable if the process does not worsen.

Are there hunger pills?

Say goodbye to spots, wrinkles, freckles and warts!

A compress of onion, garlic and aloe will help with joint pain.

Lose weight with lentil dishes

How is the spine connected to other organs?

Flaxseed oil for weight loss

Folk remedies for weight loss

Apple cider vinegar for weight loss

To avoid health problems, we strongly recommend that you consult a doctor before using advice from our website.

Digestion in the stomach

Pharynx and esophagus

Chopped food moistened with saliva, taking more convenient form for swallowing, moves to the root of the tongue and enters the pharynx, then into the esophagus.

Swallowing is a rather complex process in which many muscles take part, and to a certain extent it is carried out reflexively.

The esophagus is a four-layer tube, the length of which is cm. At rest, you can see a gap in it in the form of a gap, but food or drinks do not fall through, but move forward with the help of wave-like contractions of its walls. At the same time, salivary digestion occurs in the food bolus.

The remaining organs of the gastrointestinal tract are located in the abdomen, separated from the chest by the diaphragm, the main respiratory muscle. Through a special hole in it, the esophagus penetrates into the abdominal cavity and further into the stomach.

The entrance from the esophagus to the stomach is closed using a special esophageal valve (sphincter). Passing from 2 to 9 centimeters inside the organ and stretching it, food opens the entrance to the stomach. After it moves into it, the valve closes until the next intake.

However, some pathological conditions cause incomplete closure of the esophageal sphincter when acidic contents begin to penetrate into it from the stomach. This is accompanied by heartburn. The valve may also open during vomiting as a result of sudden contractions of the stomach, diaphragm and abdominal muscles.

In the gastrointestinal tract there are approximately 35 similar valves (sphincters) at the boundaries of its individual segments. Thanks to them, the contents of a separate part digestive system moves in the desired direction, undergoes chemical treatment - it is broken down and absorbed, in addition, they prevent reverse stroke processed substances. Thus, each section of the digestive tract retains its inherent chemical environment and bacterial composition.

Digestion in the stomach

The stomach is hollow organ, shaped like a retort. There are several folds in its inner mucous surface. Therefore the volume empty organ is approximately 50 ml, but it has the ability to stretch and hold up to 3 -4 liters.

Once in the stomach, the food bolus is subjected to mechanical and chemical effects for several hours, depending on its composition and quantity.

The mechanical effect is as follows. The walls of the stomach contain smooth muscles, which have several layers: longitudinal, oblique and circular. By contracting, the muscles better mix food with digestive juice, and also move it from the stomach to the intestines.

Among food products, alcohol, excess water, glucose, salts, penetrating into the body, can be absorbed immediately, this is due to concentration and combination with other products without chemical treatment.

But chemical changes are in progress digestion in the stomach affect the bulk of what is eaten, and this is carried out under the influence of gastric juice synthesized by the glands. They are located in the mucous membrane of the organ, and their number is about 35 million. Each square millimeter of the mucous membrane contains approximately 100 gastric glands. There are 3 types of gland cells: main - synthesizing enzymes, lining - hydrochloric acid and additional - mucus.

Food entering the stomach envelops it inner surface, located in the shape of a cone. Moreover, gastric juice acts mainly on the surface layers that are in contact with the mucosa. Saliva enzymes continue to act inside the food bolus for a long time until the stomach juice completely saturates it and destroys amylase. As a rule, with regular mixed food this takes up to 30 minutes.

Composition of gastric juice

The composition of gastric juice includes enzymes that break down fats and proteins, hydrochloric acid and mucus.

Hydrochloric acid of gastric juice

During digestion in the stomach, the main role is played by hydrochloric acid of gastric juice. It increases the activity of enzymes, causes denaturation (loss of natural properties due to disruption of the structure of molecules) and swelling of proteins, promoting their fragmentary breakdown, in addition, it has bactericidal functions. Hydrochloric acid destroys the bulk of bacteria that enter the stomach with food, preventing or slowing down the decay process.

Gastric juice enzymes

The main enzyme in gastric juice is pepsin, which is responsible for the breakdown of proteins during digestion in the stomach. Enzymes are substances of protein nature that ensure the occurrence of any reaction. As gastric juice penetrates into the food mass, proteolysis occurs mainly - the process of protein breakdown. Pepsin converts proteins into peptones and albumoses using hydrochloric acid.

Stomach mucus

Mucus, which is synthesized by the cells of the gastric mucosa, prevents mechanical and chemical damage to the lining of the organ.

Digestion in the stomach: mechanism for separating gastric juice

The amount and composition of gastric juice is determined by the nature of the food and its chemical composition. It is curious that the stomach seems to know in advance what kind of work it has to do, secreting the necessary juice in advance, guided only by one type or smell of food. This fact was proven by academician I.P. Pavlov in experiments with dogs, and in humans, only the mental image of food causes the synthesis of gastric juice. The mechanism of secretion of juice in the stomach is explained by a complex of conditioned and unconditioned reflexes.

For digesting curdled milk, fruits and other light food a small amount of low acidity gastric juice with a low enzyme content is required. For meat, meat products with spicy seasonings necessary copious discharge juice rich in enzymes high acidity within 7-8 hours. Bread releases less juice, and it contains many enzymes, but the juice separation is h. The separation of gastric juice into milk lasts six hours, its largest volume occurs in the 3rd and 4th hours, the delayed separation is caused by the presence of fat.

Fatty foods inhibit gastric secretion, simultaneously reducing the digestive power of gastric juice. If you rationally combine various foods, this will make it possible to maintain a high level of gastric juice secretion for a long time.

Eating mainly carbohydrate foods (cereals, bread, vegetables, potatoes) for a long time leads to a decrease in the secretion of gastric juice. Conversely, the predominant consumption of meat and meat products increases secretion. This affects both its volume and acidity. During the day, on average, 2 - 2.5 liters of juice are produced.

As a rule, the residence time of food in the stomach ranges from 4 to 11 hours. Fatty and protein-rich foods stay in the stomach for 8 – 10 hours; they are evacuated longer than rich in carbohydrates. Liquids do not linger in the stomach, beginning to pass into the intestines almost immediately after they arrive.

Transition of food into the duodenum

As a portion of food located at the walls of the stomach is digested, it, thanks to the motor function of the organ, begins to move to the muscular valve (sphincter) at the entrance to the duodenum. As a result, food enters it in the form of an almost homogeneous semi-digested gruel. The sphincter reflexively relaxes and contracts due to the action of hydrochloric acid. When the gruel is neutralized by the alkaline content in the duodenum, the valve opens and the next portion comes in again. That is, the transition is carried out gradually and in portions, which ensures better processing of digestive juices in the small intestine.

10.3.1.The main site of lipid digestion is upper section small intestine. For the digestion of lipids, the following conditions are necessary: ​​· the presence of lipolytic enzymes; · conditions for lipid emulsification; Lipase is active in the stomach. Lipases belong to the class of hydrolases; they hydrolyze ester bonds -O-CO- to form free fatty acids, diacylglycerols, monoacylglycerols, glycerol (Figure 10.3). These acids can be re-secreted with bile into the intestines and participate in the processes of digestion and absorption. Such enterohepatic circulation of bile acids can occur up to 10 or more times a day.