Basic patterns of metabolic processes in the human body. Part 2.

Some people believe that carbohydrates, fats and proteins are always completely absorbed by the body. Many people think that absolutely all the calories present on their plate (and, of course, counted) will enter the bloodstream and leave their mark on the body. In reality, everything is different. Let's look at the absorption of each macronutrient separately. Digestion (assimilation) is a set of mechanical and biochemical processes through which the food absorbed by a person is converted into substances necessary for the functioning of the body.

The digestion process usually begins in the mouth, after which the chewed food enters the stomach, where it undergoes various biochemical treatments (mainly protein is processed at this stage). The process continues in the small intestine, where, under the influence of various food enzymes, carbohydrates are converted into glucose, lipids are broken down into fatty acids and monoglycerides, and proteins into amino acids. All these substances, absorbed through the intestinal walls, enter the blood and are distributed throughout the body.

Macronutrient Absorption

Absorption of macronutrients does not last for hours and does not stretch across the entire 6.5 meters of the small intestine. The absorption of carbohydrates and lipids by 80%, and proteins by 50%, occurs throughout the first 70 centimeters of the small intestine.

Absorption of carbohydrates

Different types
of carbohydrates are absorbed differently because they have different chemical structures
. To visualize this difference and the principles of digestion, the main steps for simple and complex carbohydrates are presented in the infographic below.

A high glycemic index of a product means that as a result of its digestion, the rise in blood glucose levels will be significant. low glycemic index indicates that its absorption by the body will change the blood glucose level slightly.

In order to determine the glycemic index of a product, take a portion containing 50 g or 25 g of carbohydrate to be digested (i.e., all indigestible carbohydrates in the product are subtracted). These products are usually offered to a group of 8-10 people who have not eaten since the day before (i.e., have been fasting overnight). Blood sugar measurements (using a finger prick method) are taken at intervals of 15-30 minutes for two hours.

The measurement results allow you to reproduce a graph (see picture), in which the entire area under the resulting curve reflects the overall increase in blood sugar levels. This value is divided by the number obtained from the standard (glucose or white bread) and multiplied by 100 to obtain a percentage value.

In the graph you can see how foods with different GI values ​​change blood glucose levels after consumption. A breakfast with a high glycemic index has a high peak in the rise in glucose levels, while a breakfast with a low GI has a flatter curve.

It is important to note that peak glycemia occurs at approximately the same time for all types of carbohydrates, regardless of whether their molecule composition is complex or simple.

Thus, the popular concepts of fast and slow carbohydrates are not correct. Many studies have shown that in the original theory, the rate of glucose entering the blood was mistakenly taken for the rate of digestion, which actually differs between different carbohydrates.

Over the past three decades, researchers have measured the glycemic index of several thousand foods.

It is important to understand that the glycemic index is not a constant value.

. Its value depends on a number of parameters: origin, variety and variety of the product (for cereals, fruits), degree of ripening (for fruits), thermal and hydrothermal treatment, type of product processing (crushing, grinding to flour), as well as the individual characteristics of each person’s body and other factors.

The glycemic index of certain foods may also depend on what they are eaten with.

. Olive oil or something acidic, such as vinegar or lemon juice, can slow down the conversion of starch to sugar and thus lower the glycemic index.

“Some foods (eg carrots, watermelon) have a high GI, but a standard serving contains so few carbohydrates that the effect on blood sugar levels is negligible. Others (such as soda) have a moderate GI because they contain enough fructose, which has a relatively minor effect on blood sugar. But they can also contain large amounts of glucose, which raises blood sugar levels,” warns Dr. Frank Hu, professor of nutrition and epidemiology at the Harvard School of Public Health.

The main proteolytic enzyme pancreatin

There are a number of enzymes that are actively involved in the digestion process and also successfully relieve any inflammatory processes. These also include pancreatin, which minimizes the negative impact of a person’s allergies to certain products. Also, if internal diseases occur, pancreatin is best suited for their treatment. However, people who experience enzyme deficiency are recommended to use drugs that contain several different enzymes. They can safely be classified as active biological additives. But such medications must be taken very carefully and observed at a certain frequency. It is still advisable to do this on the strong recommendation of the attending physician in accordance with his instructions. There is no point in showing your own initiative in this situation. This is especially dangerous to do if a person is not endowed with certain knowledge in the field of medicine. Remember, self-medication can only aggravate the situation, and it is impossible to determine the lack of protein and enzymes in the body without medical intervention. Be healthy!

Glycemic load

In addition to GI, nutritionists also proposed to take into account the glycemic load of foods (GL)

.

Glycemic load (GL) takes into account both the GI of a product and the amount of carbohydrates in it. Often foods with a high GI will have a low GI. Formula for calculating GN:

Example:

• Ready zucchini (GI=75). GN = 75*4.9/100 = 3.68.
• Wheat bagel (GI=72). GN = 72*58.5/100=42.12.

Scale of GBV levels:

• GN≤10
  – minimum level;
• GN = 11-19
  - moderate level;
• GN ≥20
  – increased.

In recent years, an opinion has emerged in the scientific community about the need to revise the assessment of GI.

Research shows that GI and GN are not sufficiently reliable criteria for selecting carbohydrate-containing products, since they do not allow high accuracy

optimize glucose levels when planning your diet.

Glycemic index of foods and weight loss

There is ample scientific evidence that nutritional systems based on low GI foods can have a positive effect on weight loss. There are many biochemical mechanisms that are involved in this, but we will name the most relevant for us:

1. Low GI foods make you feel more full than high GI foods.
2. After consuming foods with a high GI, insulin levels rise, which stimulates the absorption of glucose and lipids into muscles, fat cells and the liver, while simultaneously stopping the breakdown of fats. As a result, the level of glucose and fatty acids in the blood drops, and this stimulates hunger and more food intake.
3. Foods with different GIs have different effects on fat breakdown during rest and during sports training. Glucose from low GI foods is not as actively stored in glycogen, but during exercise, glycogen is not burned as actively, which indicates an increased use of fats for this purpose.

• The more crushed the product is (mostly grains), the higher the GI of the product.
• The more fiber a product contains, the lower its GI.

The differences between wheat flour (GI 85) and wheat grain (GI 15) fall under both of these criteria. This means that blood glucose levels rise more sharply after eating flour than after eating whole grains such as bulgur or spelt.

• The more fiber a product contains, the lower its GI.
• The amount of carbohydrates in a product is no less important than GI.

Beets are a higher fiber source of carbohydrates than flour. Although it has a high glycemic index, it is low in carbohydrates, meaning it has a lower glycemic load. In this case, despite the fact that its GI is the same as that of a grain product, the amount of glucose entering the blood will be much less. When we compare whole crops to processed ones, it is important to remember all the micro and phytonutrients that are present in natural foods that are not found in industrially processed foods.

• The GI of raw vegetables and fruits is lower than that of cooked ones.

This rule applies not only to carrots, but also to all vegetables with a high starch content, such as sweet potatoes, potatoes, beets, etc. During cooking, a significant part of the starch is converted into maltose (a disaccharide), which is very quickly absorbed.

Therefore, it is better not to boil even boiled vegetables, but to ensure that they remain whole and firm. However, if you have diseases such as gastritis or stomach ulcers, it is still better to eat cooked vegetables.

• The combination of proteins with complex carbohydrates reduces the GI portion.

Vegetables contain dietary fiber and complex carbohydrates, which are not absorbed by the body, but are very important for effective digestion. Additionally, adding protein to any type of carbohydrate will lower the overall GI of the dish.

Natural products, unlike juices, contain fiber and thereby lower the GI. Moreover, it is advisable to eat fruits and vegetables with the skin, not only because the skin contains fiber, but also because most of the vitamins are located directly on the skin.

Trypsin: enzyme function

What is trypsin? This is another kind of enzyme that breaks down proteins and peptides. At the same time, it has the function of hydrolyzing esters. The main function of trypsin is that it perfectly controls the digestive process.

Trypsin treats diseases such as bronchitis, pneumonia, and sinusitis. It can also be used for burns, in the presence of various purulent wounds, as well as after operations. In dentistry, for diseases of the oral cavity, this drug is also very useful.

Side effects that may occur when using trypsin are associated with an increase in body temperature. If trypsin was administered by inhalation, irritation of the mucous membrane of the upper respiratory tract may occur.

It is advisable to use trypsin, the function of which is discussed in the article, no more than twice a day, 0.01 grams. Children are recommended to consume it once a day, and only 0.0025 grams.

After treating the wound with alcohol or brilliant green, you can also apply a cloth soaked in trypsin. Such a canvas should remain in the damaged area for at least 24 hours. In this situation, trypsin (an enzyme that breaks down proteins and peptides) serves as a kind of protection against various types of infections.

Protein absorption

The process of digesting proteins requires increased acidity in the stomach. Gastric juice with high acidity is necessary to activate the enzymes responsible for the breakdown of proteins into peptides, as well as for the primary dissolution of food proteins in the stomach. From the stomach, peptides and amino acids enter the small intestine, where some of them are absorbed through the intestinal walls into the blood, and some are further broken down into individual amino acids.

To optimize this process, it is necessary to neutralize the acidity of the gastric solution, and the pancreas is responsible for this, as well as the bile produced by the liver and necessary for the absorption of fatty acids.

Proteins from food are divided into two categories: complete and incomplete.

Complete proteins are proteins that contain all the amino acids necessary (essential) for our body. The source of these proteins is mainly animal proteins, i.e. meat, dairy products, fish and eggs. The exception is soy protein, which is similar in amino acid composition to meat protein. Among cereals, the leader in the content of essential amino acids is quinoa.

Incomplete proteins contain only a portion of the essential amino acids. It is believed that legumes and cereals themselves contain incomplete proteins, but their combination allows us to get all the essential amino acids.

In many national cuisines, the correct combinations leading to adequate protein consumption arose naturally. Thus, in the Middle East, pita with hummus or falafel (wheat with chickpeas) or rice with lentils is common; in Mexico and South America, rice is often combined with beans or corn.

One of the parameters that determines protein quality is the presence of essential amino acids . In accordance with this parameter, there is a product indexing system.

For example, the amino acid lysine is found in small quantities in cereals, and therefore they receive a low score (cereals - 59; whole wheat - 42), and legumes contain small amounts of the essential methionine and cysteine ​​(chickpeas - 78; beans - 74; legumes – 70). Animal proteins and soy receive a high rating on this scale, as they contain the necessary proportions of all essential amino acids (casein (milk) - 100; egg white - 100; soy protein - 100; beef - 92).

In addition, it is necessary to take into account the protein composition , their digestibility from a given product, as well as the nutritional value of the entire product (the presence of vitamins, fats, minerals and calorie content). For example, a hamburger will contain a lot of protein, but also a lot of saturated fatty acids, so its nutritional value will be lower than that of a chicken breast.

Proteins from different sources and even different proteins from the same source (casein and whey protein) are utilized by the body at different rates [5].

Nutrients from food are not 100% digestible. The degree of their absorption can vary significantly depending on the physicochemical composition of the product itself and the products absorbed simultaneously with it, the characteristics of the body and the composition of the intestinal microflora.

What are the main functions of protein?

So, what functions do proteins perform in the body? The following can be distinguished:

• catalytic function - with its help it is possible to control one or another chemical reaction occurring in biological systems;
• transport function - transfer to all organs and tissues of the oxygen they need;
• the protective function is based on the fact that protein in the blood has a tendency to clot, which protects the human body from excessive blood loss in the event of possible injuries;
• the contractile function is responsible for the contraction of the muscles of the human body with the direct participation of the proteins actin and myosin;
• structural function ensures the formation of biomembrane cells;
• hormonal function ensures the correct division of nutrients within the body with the help of hormones;
• The nutritional function provides, with the help of proteins, the required amount of calories for human life, and this is what gives him the opportunity to obtain the necessary energy and physical strength.

Digestion of fats

Fat entering the body passes through the stomach almost intact and enters the small intestine, where there are a large number of enzymes that convert fats into fatty acids. These enzymes are called lipases. They function in the presence of water, but this is problematic for fat processing, since fats do not dissolve in water.

In order to be able to utilize fats, the body produces bile. Bile breaks up fat clumps and allows enzymes on the surface of the small intestine to break down triglycerides into glycerol and fatty acids.

Transporters for fatty acids in the body are called lipoproteins . These are special proteins that are capable of packaging and transporting fatty acids and cholesterol throughout the circulatory system. Next, fatty acids are packaged in fat cells in a fairly compact form, since their assembly (unlike polysaccharides and proteins) does not require water [9].

The proportion of fatty acid absorption depends on the position it occupies relative to glycerol. Those fatty acids that occupy the P2 position are absorbed better. This is due to the fact that lipases have different degrees of effect on fatty acids depending on the location of the latter.

Not all fatty acids supplied with food are completely absorbed by the body, as many nutritionists mistakenly believe. They may not be partially or completely absorbed in the small intestine and may be excreted from the body.

For example, in butter, 80% of fatty acids (saturated) are in the P2 position, that is, they are almost completely absorbed. The same applies to fats that are part of milk and all dairy products that do not undergo the fermentation process.

The fatty acids present in mature cheeses (especially long-aged cheeses), although saturated, are still located in the P1 and P3 positions, which makes them less absorbable.

In addition, most cheeses (especially hard ones) are rich in calcium. Calcium combines with fatty acids to form “soaps” that are not absorbed and are excreted from the body. The ripening of cheese promotes the transition of its fatty acids to the P1 and P3 positions, which indicates their weak absorption [10].

We write in more detail about the types of fats and their characteristics in the article “Fats”.

Authors: Elena Degtyar, PhD; Kardakova Maria, MSc

Literature

1. Mann (2007) FAO/WHO Scientific Update on carbohydrates in human nutrition: conclusions. European Journal of Clinical Nutrition 61 (Suppl 1), S132–S137 2. FAO/WHO. (1998). Carbohydrates in human nutrition. Report of a Joint FAO/WHO Expert Consultation (Rome, 14–18 April 1997). FAO Food and Nutrition Paper 66 3. Holt, S. H., & Brand Miller, J. (1994). Particle size, satiety and the glycemic response. European Journal of Clinical Nutrition, 48(7), 496–502. 4. Jenkins DJ (1987) Starchy foods and fiber: reduced rate of digestion and improved carbohydrate metabolism Scand J Gastroenterol Suppl.129:132-41. 5. Boirie Y. (1997) Slow and fast dietary proteins modulate postprandial protein accretion differently. Proc Natl Acad Sci US A. 94(26):14930-5. 6. Popkin, BM (2012) Global nutrition transition and the pandemic of obesity in developing countries. Nutrition reviews 70 (1): pp. 3 -21. 7. Your Meta Body's bolism 8. About Glycemic Index 9. International table of glycemic index and glycemic load values: 2002 10. Jenkins, DJ, Wolever, TM, Taylor, RH, Barker, H., Fielden, H., Baldwin, J. M., ... & Goff, D. V. (1981). Glycemic index of foods: a physiological basis for carbohydrate metabolism. The American journal of clinical nutrition, 34(3), 362-366. 11. How to use the GI table when creating a menu for diabetics.