Why do humans need polyunsaturated fatty acids? Unsaturated fatty acids in foods

Foreword

So, what are these mysterious omega fats and why is it so important for every thinking person who cares about their health and the health of their children to know about them.

Nowadays, products that do not contain fat or contain it in minimal quantities have become very popular.
Did you know that fats can be not only not harmful, but also vital for health?
We will talk about polyunsaturated essential fatty acids (PUFAs) or vitamin F. Vitamin F was discovered in the late 1920s by George and Mildred Burr. In those years, their discovery did not make a big impression in science. However, in recent decades, interest in vitamin F has revived. During this time, a large amount of information has accumulated about the importance of polyunsaturated fats for human health. PUFAs cannot be synthesized by the human body and therefore must always be part of our food. They are essential for the proper growth and functioning of the human body.

Of greatest interest to us now are the omega-3 and omega-6 PUFA families.

Historically, the content of omega-3 and omega-6 fats in the diet of people has been balanced. This was achieved through a large amount of green leafy vegetables in the diet, containing small amounts of omega-3. In the meat of animals that our ancestors ate, a balance of PUFAs was also observed, since the same leafy plants were the main food for animals.
Today, farm-raised meat contains large amounts of omega-6s and negligible amounts of omega-3s. Cultivated vegetables and fruits also contain lower amounts of omega-3s than wild plants. In the last 100 to 150 years, the amount of omega-6 in the diet has also increased significantly due to the large consumption of vegetable oils such as corn, sunflower, safflower, cottonseed and soybean. The reason for this is the recommendation to replace saturated fats with vegetable oils to lower blood cholesterol levels. Consumption of fish and seafood rich in omega-3 fats has been significantly reduced. In the modern Western diet, the ratio of omega-6 to omega-3 is in the range of 10–30:1 instead of the traditional 1–4:1.

Table 1. Types of fats.

Note: Rapeseed oil is high in both monounsaturated and polyunsaturated fatty acids, so it is included in both categories.

Description of omega-3 and omega-6 PUFAs

The parent acid of the omega-3 PUFA family is alpha-linolenic acid. ALC, the parent acid of the omega-6 family is linoleic acid OK.

In a healthy body, in the presence of the required amount of enzymes, linoleic acid is converted into gamma-linolenic acid. GLK.
Gamma-linolenic acid is the precursor of dihomo-gamma-linolenic acid DGLK, the parent of the first series of prostaglandins, as well as the precursor of arachidonic acid AK, the parent of the second series of prostaglandins.

Alpha-linolenic acid is converted to eicosapentaenoic acid EPC, the parent of the third series of prostaglandins, and docosahexaenoic acid DHA.

Arachidonic AK and docosahexaenoic DHA acids belong to long-chain PUFAs (LCPUFAs). They are important structural components of phospholipid membranes in tissues throughout the body and are especially abundant in the tissues of the brain and nervous system. The amount of DHA in most human tissues is small in percentage terms, but in the retina, brain and sperm DHA is up to 36.4% of all fatty acids. With a prolonged lack of LA and ALA in the diet, or insufficient conversion of them, the amount of long-chain PUFAs in the brain and nervous system may decrease.

Table 2. Families of omega-6 and omega-3 PUFAs.

Sometimes the body cannot break down LA and ALA due to some defects or a lack of desaturase and elongase enzymes necessary for cleavage. In such cases, it is necessary to introduce foods rich in GLA, DGLA (omega-6), for example, borage oil, evening primrose oil (borage oil, evening primrose oil) and EPA, DHA (omega-3) - fish oil, oily fish.

The effect on the body of derivatives of omega fats

PUFAs play another equally important role in the body. Eicosanoids (prostaglandins, prostacyclins, thromboxanes and leukotrienes) are synthesized from them. Eicosanoids are local tissue hormones. They do not travel in the blood like regular hormones, but are created in cells and regulate numerous cellular and tissue functions, including platelet concentration, inflammatory responses and leukocyte function, vasoconstriction and dilation, blood pressure, bronchial contractions, and uterine contractions.
To make it clearer to you the effect of different families of PUFAs on the body, below I give a table of examples of the physiological action of prostaglandins of different series. Prostaglandins are divided into three series: 1, 2 and 3.
Prostaglandins 1 and 2 series are synthesized from omega-6 acids, prostaglandins 3 series - from omega-3 acids.

Table 3. Examples of the physiological action of prostaglandins 1, 2 and 3 series

Often, series 2 prostaglandins are conditionally called "bad", and series 1 and 3 are called "good". However, it is wrong to conclude from this that omega-3 fats are healthy and omega-6 are harmful. A balance of omega-3 and omega-6 fats in the body is essential for optimal health.
Due to the significant predominance of omega-3 fats in the diet (more than 7-10 g / day), for example, Greenland Eskimos have an increased tendency to various bleeding.
It is fair to say here that a large overabundance of omega-6s still has worse health consequences.
In general, omega-6 deficiency often results in skin manifestations such as dry, thickened, scaly skin and stunted growth. Also possible: skin rashes similar to eczema, hair loss, degeneration of the liver, kidneys, frequent infections, poor wound healing, infertility.
Omega-3 deficiency has less noticeable clinical symptoms, including neurodevelopmental abnormalities, abnormal visual functioning, and peripheral neuropathy.

As noted above, the diet of most modern people contains too much omega-6 and too little omega-3 PUFAs. An excess of AA arachidonic acid (from the omega-6 PUFA family) in tissues plays a negative role in the development of inflammatory processes and an increase in susceptibility to certain diseases.
The following is a partial list of diseases that can be prevented or improved by adding omega-3 PUFAs to the diet. The diseases are listed in descending order of strength of evidence:

1. coronary heart disease and stroke;
2. PUFA deficiency in infancy (development of the retina and brain);
3. autoimmune diseases (eg, lupus and nephropathy);
4. Crohn's disease (inflammatory bowel disease);
5. breast, colon and prostate cancer;
6. slightly increased pressure;
7. rheumatoid arthritis (4).

Other sources also mention bronchial asthma, type 2 diabetes, kidney disease, ulcerative colitis, chronic obstructive pulmonary disease (15); critically ill patients with lung damage, eczema, attention deficit hyperactivity disorder in children, dyslexia, allergic rhinitis, depression, including postpartum depression, and even schizophrenia and some other mental illnesses. Not for all of these diseases, the results of the use of omega acids are established precisely, the study continues. For some of these diseases, the addition of DGLA and GLA from the omega-6 PUFA family to the diet is also used.

Omega fats in infant formula

There is now great interest in the addition of long-chain PUFAs to infant formulas. The presence of large amounts of DHA and AA in retinal and brain tissues, as well as the presence of these LCPUFAs in breast milk, is suggestive of their role in infant development. Various studies have shown that breastfeeding in early childhood is associated with greater cognitive development in late childhood; that retinal and brain function matures faster in breastfed babies; the intelligence quotient is higher in children fed with women's breast milk. It is very likely that the difference in the amount of long-chain PUFAs received during infancy is responsible for these differences, although it cannot be ruled out that there are also other factors that are still unknown to science.

Soybean oil (a 7:1 ratio of LA to ALA) has been added to modern blends to significantly improve their omega-3 status. Previously, blends were made only with corn and coconut oils, which are rich in omega-6s and contain negligible amounts of omega-3s. But - there is still debate whether the baby's body can convert LA and ALA into long-chain PUFAs? And is it necessary to add arachidonic and docosahexaenoic acids to the mixture?

It is known that during pregnancy, AA and DHA are transferred to the blood of the fetus through the placenta. There are two critical moments in a child's development when he needs omega LCPUFA - during fetal development and after childbirth, until the biochemical development of the retina and brain is completed. If a pregnant woman does not consume enough omega-3 fats with food, her body removes them from its own stores. Especially high requirements for the presence of DHA and AA in the body of a pregnant woman in the third trimester of pregnancy, when there is a rapid growth of the brain of the fetus. During pregnancy, the concentration of omega-3 LCPUFA in the mother's blood plasma changes little, but in the postpartum period there is a gradual decline, independent of breastfeeding, sometimes long-term. This decline can be halted or prevented with timely dietary adjustments (DHA 200-400 mg/day). Maternal plasma levels of DHA may continue to decline with each successive pregnancy.

Term babies are born with a body fat store of approximately 1,050 mg of DHA. During the first 6 months of life, breastfed infants continue to increase the amount of DHA in the body at a rate of 10 mg/day, with about 48% of DHA deposited in brain tissue. During this time, artificial people accumulate in the brain only about half of the DHA accumulated by breastfed babies and in the process lose DHA stores in the body. To date, there is no evidence that artificial formulas can convert ALA to DHA in sufficient amounts during infancy (14). Many studies have concluded that during infancy (up to approximately 6 months) DHA should be considered an essential element along with LA and ALA. Infants fed formulas not fortified with long-chain PUFAs have lower proportions of DHA (as well as AA) in plasma, erythrocytes, and brain than those fed breast milk. Infants fed fortified formulas do not achieve the same levels of DHA in the body as those fed with breast milk, however, relative to artificial formulas on ordinary formulas, their DHA status is much improved. It is possible that these amounts of DHA accumulated by artificers are sufficient for their optimal development. It is known that already deposited LCPUFAs are retained in the retina and brain with enviable strength, even if the diet is subsequently poor in omega-3 fats.

Human breast milk always contains small amounts of DHA and AA (0.3% and 0.44% of total fat, respectively) along with LA, ALA and small amounts of other omega acids. The amount of DHA in milk depends on the mother's diet.
When sources of omega-3 fats are introduced into the mother's diet, the concentration of DHA in the mother's breast milk and the baby's blood increases.

A significant positive effect of the addition of DHA and AA in the mixture on the development of infants has been established for premature babies (especially in the functioning of vision). Since the greatest accumulation of DHA by the fetus occurs in the third trimester of pregnancy, premature babies are born with a large lack of DHA in the brain and body. Naturally, they respond most gratefully to the addition of the missing DHA to their diet. However, there are no answers regarding the safety and need to add AA and DHA to formulas for term infants.
Different studies come up with different results, which are difficult to compare. Different design of the studies, the choice of different mixtures, the addition of different amounts of different omega-3 PUFAs, sometimes accompanied by the addition of AA (omega-6), sometimes not, the different tests used by the researchers do not allow unambiguous interpretation of the results of these studies.
To date, no reliable standardized tests have been developed to assess the impact of long-chain PUFA supplementation on child development.
Minimum requirements for PUFAs are difficult to establish because:
1) long-chain PUFAs can be synthesized from ALA, LA;
2) the concentrations of omega-6 and omega-3 LCPUFAs are not clearly defined, showing their deficiency or sufficiency;
3) there are no recognized clinical tests to determine the deficiency and sufficiency of omega-3 LCPUFA.

The issue is further complicated by the fact that some studies show that adding too much omega-3 DHA and ALA to a blend can lead to insufficient conversion of omega-6 acids (due to the simultaneous increase in EPA (omega-3), which rivals AA ( omega-6)), which can result in slow growth, later development of speech, changes in the development of the nervous system in a positive or negative direction.
The simultaneous addition of AA to the mixture of arachidonic acid should neutralize this negative effect.

Conclusion: Until there is a specific measure of the outcome of infant PUFA supplementation (e.g. visual acuity, cognitive development comparison scores, insulin sensitivity index, height) in relation to blood concentrations of various PUFAs, the composition of breast milk from healthy mothers should be targeted. , including fish in their meals, as an example of dietary recommendations for infants.

In Europe, infant formulas fortified with AA and DHA in amounts similar to those found in human breast milk have already appeared on the market. Unfortunately, the addition of LCPUFA increases the cost of mixtures. Fortified formulas are not yet available in the US.

Omega fats in foods

The main sources of omega-3 fats are fish and vegetable oils. Fish is rich in EPA and DHA, vegetable oils are rich in ALA.
Other sources include nuts, seeds, vegetables, some fruits, egg yolk, poultry, and meat: these sources contribute negligible amounts of omega-3s to the diet.

Of the commonly available oils, rapeseed (canola or rapeseed oil) and soybean (soybean oil) oils are the richest in ALA, 9.2% and 7.8% ALA, respectively. Flaxseed oil contains especially large amounts of ALA, but it is not one of the commonly consumed oils.

Mackerel, herring, and salmon are isolated from oily fish containing large amounts of EPA and DHA. For example, raw salmon contains 1.0–1.4 g omega-3 fats/100 g serving, mackerel contains ~2.5 g omega-3 fats/100 g serving. The fat content can vary depending on the type of fish, different varieties of salmon, for example, contain different amounts of fat. Other less fatty fish contain much lower amounts of omega-3 fats.

Of the animal products fortified with omega-3 PUFAs, only eggs (omega-3 eggs) are currently available on the market.

Table 4. Content of omega-3 PUFAs in selected marine products.

Note: Be aware that some types of fish contain large amounts of mercury.
The United States and Canada recommend that pregnant, breastfeeding mothers, and young children avoid the following types of fish: shark, swordfish, king mackerel (shark, swordfish, king mackerel, tilefish), tuna steaks in question (tuna steaks), or at least not eat them more than once a month. Other people should not eat these types of fish more than once a week.
You can eat other types of fish, from canned tuna to shellfish, crustaceans and smaller ocean fish. However, try to eat different types of fish and not the same one. Some US states recommend that pregnant women eat no more than 198 grams (7 ounces) of canned tuna per week.

Table5. Plant sources of ALA.

Note: The table lists only the most significant plant sources of omega-3 PUFAs. Other plants contain smaller amounts of omega-3 PUFAs.

Omega-3 PUFA dietary supplements

A variety of nutritional supplements containing omega-3 PUFAs are now available to consumers. Many are made from marine oils and contain 180 mg of EPA and 120 mg of DHA per capsule.
Another source of omega-3 PUFAs is cod liver oil, typically 173 mg EPA and 120 mg DHA per capsule. These supplements should be taken with caution, keeping in mind that they contain large amounts of vitamins A and D. A vegetarian source of DHA (100mg per capsule) extracted from seaweed (algae) is also now available.

Canada recommends an intake of 1.2–1.6 g/day of omega-3 fats, which is similar to the US recommendation, but does not distinguish between different omega-3 fats.
The UK recommends that 1% of energy be ALA and 0.5% EPA + DHA.
The Commission on Medical Aspects of Nutrition Policy, which includes the UK, recommends EPA and DHA combined at 0.2 g/day.
Australia recommends a modest increase in plant-based (ALA) and fish (EPA and DHA) sources of omega-3 fats.
Finally, the NATO Preliminary Symposium on Omega-3 and Omega-6 Fatty Acids recommended that EPA and DHA be taken together as 0.27% of energy or 0.8 g/day.

Some recommendations have been made based on the ratio of omega-6 fats to omega-3 fats.
The WHO recommends an omega-6 to omega-3 ratio of 5-10:1.
Sweden recommended 5:1, while Japan changed the recommendation from 4:1 to 2:1 (5).

To achieve the suggested recommendations for both grams and proportions, while increasing omega-3 fats in the diet, you need to reduce the amount of omega-6 fats. Because of the competition between omega-6 and omega-3 fats for elongase and desaturase enzymes, the amount of LA in the diet affects the amount of EPA and DHA converted from ALA.
Also, simply adding omega-3 fats to other types of fat already consumed can lead to weight gain over time.

Omega-3 fats, like other polyunsaturated fats, are susceptible to oxidative damage from free radicals, radiation, and toxic effects. They are the most easily damaged fats in the body. Although not yet fully understood, fat oxidation is considered to be an important mechanism involved in the pathogenesis of inflammation, cancer, and atherosclerosis. Therefore, it is often recommended to increase the amount of foods rich in vitamin E in the diet at the same time as taking omega-3 PUFAs or to take additional vitamin E. In no case should you eat already oxidized, rancid fats (any fats).
They are easily recognizable by their unpleasant smell and taste.

Foods containing large amounts of vitamin E:

Vitamin E is often found in the same plant foods that are rich in LA and ALA.
The best sources are unrefined vegetable oils, seed and nut oils, and grains. During the chemical processing (refining) of oils and grinding, refining and bleaching of flour, vitamin E is lost. Animal sources such as butter, egg yolk, milk fat, and liver contain smaller amounts of vitamin E.

Some sources of vitamin E.

Unrefined oils: safflower, sunflower, cottonseed, soybean, corn, peanut, sea buckthorn; wheat germ and oil from them; legumes; cereal and bean sprouts; soybeans, nuts, seeds, nut butters, brown rice, oatmeal, dark green leafy vegetables, green peas, spinach, asparagus.

Table 6Approximate quantities of vegetable and fish products rich in omega-3 PUFAs,according to current dietary guidelines (5)

List of foods containing significant amounts of omega-3 and omega-6 PUFAs

OMEGA-3.
ALC. flax seeds or linseed oil; walnuts, pumpkin seeds or oils from them; wheat germ oil, rapeseed oil, soybean oil (preferably unrefined), dark green leafy vegetables, especially purslane.
Olive oil, although it does not contain large amounts of omega-3, but it helps to increase the content of omega-3 in the cells of the body (according to some sources). Flaxseed oil, ground flax seeds should be stored in the dark in the refrigerator. Flaxseed oil is not used in cooking, as high temperature deprives it of its beneficial properties. Ground flaxseeds can be used in baking, especially breads.
EPA, DHA. As a general rule, the fatter the fish, the more omega-3 fats it contains. In addition to salmon, mackerel and herring, sardines, tuna, and trout are also sometimes mentioned. Here we will include fish oil and eggs with a high content of omega-3 fats.

OMEGA-6.
OK. Sunflower, safflower, corn, cottonseed, soybean oils (preferably unrefined). Raw pistachios, pine nuts, raw sunflower seeds, sesame seeds, pumpkins.
GLC. Oils of borage, evening primrose and black currant seed oil.
AK. Butter, animal fat, especially pork, red meat, offal and eggs.

Table 7. Oils with a relatively high content of omega-3 and omega-6 PUFAs.

Note: Soybean oil has the highest omega-6 PUFA content of most omega-3 oils, so it belongs to both categories.

PUFA - polyunsaturated essential fatty acids - polyunsaturated fatty acids (PUFAs).

LCPUFA - long chain polyunsaturated fatty acids long-chain polyunsaturated fatty acids (LCPUFAs).

ALC - alpha-linolenic acid from the omega-3 PUFA family - linolenic acid (ALA; 18:3n-3).

EPC - eicosapentaenoic acid from the omega-3 PUFA family - Eicosapentaenoic acid (EPA; 20:5n-3).

DHA - docosahexaenoic acid from the omega-3 PUFA family, belongs to LCPUFA - Docosahexaenoic acid (DHA; 22:6n-3).

OK - linoleic acid from the omega-6 family - Linoleic acid (LA; 18:2 n-6).

GLC - gamma-linolenic acid from the omega-6 family - Gamma linolenic acid (GLA; 18:3 n-6).

DGLK - dihomo-gamma-linolenic acid from the omega-6 family - Dihommo - gamma - linolenic acid (DGLA; 20:3 n -6).

AK- arachidonic acid from the omega-6 family, belongs to LCPUFA - Arachidonic acid (AA; 20:4n-6).

Omega is often referred to as n i.e. omega-3 = n-3, omega-6 = n-6, or w-w-3, w-6 respectively.

1. At the moment, there is no consensus on the optimal ratio of omega-3 to omega-6, as well as on the maximum allowable amounts of omega-3 in the diet, so the numbers may vary slightly in different sources.

2. Pharmaceutical borage ( Borago officinalis) – borage; primrose biennial, evening primrose, evening primrose, primrose ( Oenothera biennis, family Onagraceae) - evening primrose.

3. The cause of the above symptoms in our time is often not a lack of linoleic acid in the diet, but its insufficient splitting into subsequent fatty acids.

4. Brain development ends by the age of 6-7, but the most active period of development falls on the first and second years of a child's life.

5. There is a point of view, not yet proven, that it is this decline in DHA in the blood that explains the development of postpartum depression and emotional swings in the mood of the woman who has given birth. (Immediately after childbirth, the chances of developing serious mental disorders such as depression and obsessive-compulsive disorder increase 6-fold and remain elevated for 2 years. Gitlin MJ, Pasnau RO. Psychiatric syndromes linked to reproductive function in women: a review of current knowledge. Am J Psychiatry 1989;146(11):1413-1422).

6. In countries with a high consumption of fish, such as Japan, DHA in breast milk is typically 0.6% of total fat.

7. Fish oils, especially fish liver oils, can be contaminated with PCBs and dioxins. Seaweed fats, as a new food, are not allowed to be used in all countries yet.

8. Desaturase enzymes are also easily bound by trans fats (margarines, hydrogenated vegetable oils).

9. The US has not made official recommendations for omega-3 fat intake; the above recommendations are given by a group of American scientists. The current official recommendations refer to PUFA intake in general: 1–2% of energy from FA to prevent fatty acid deficiency and total PUFA intake should be 7% of energy and not exceed 10% of energy.

1. Richard S. Lord, Ph.D. and J. Alexander Brally, Ph.D., C.C.N. Clinical Applications of Fatty Acid Profiling. MetaMetrix, Inc., Norcross, GA.

2.Canadian Asthma Prevention Institute. Prostaglandins, Enzymes and Cells.

3. Reto Muggli. Preface. Am J Clin Nutr 2000 71: 169-170.

4. William E Connor. Importance of n-3 fatty acids in health and disease. Am J Clin Nutr 2000 71: 171-175.

5. PM Kris-Etherton, Denise Shaffer Taylor, Shaomei Yu-Poth, Peter Huth, Kristin Moriarty, Valerie Fishell, Rebecca L Hargrove, Guixiang Zhao and Terry D Etherton. Polyunsaturated fatty acids in the food chain in the United States. Am J Clin Nutr 2000 71: 179-188.

6. Jan Eritsland. Safety considerations of polyunsaturated fatty acids. Am J Clin Nutr 2000 71: 197-201.

7 Sheila M Innis Essential fatty acids in infant nutrition: lessons and limitations from animal studies in relation to studies on infant fatty acid requirements . Am J Clin Nutr 2000 71: 238-244.

8. Ricardo Uauy and Dennis R Hoffman. Essential fat requirements of preterm infants. Am J Clin Nutr 2000 71: 245-250.

9. Robert A Gibson and Maria Makrides. n-3 Polyunsaturated fatty acid requirements of term infants . Am J Clin Nutr 2000 71: 251-255.

10. M. A. Crawford. Placental delivery of arachidonic and docosahexaenoic acids: implications for the lipid nutrition of preterm infants . Am J Clin Nutr 2000 71: 275-284.

11. Monique DM Al, Adriana C van Houwelingen, and Gerard Hornstra. Long-chain polyunsaturated fatty acids, pregnancy, and pregnancy outcome . Am J Clin Nutr 2000 71: 285-291.

12. Craig L Jensen, Maureen Maude, Robert E Anderson, and William C Heird. Effect of docosahexaenoic acid supplementation of lactating women on the fatty acid composition of breast milk lipids and maternal and infant plasma phospholipids. Am J Clin Nutr 2000 71: 292-299.

13. John R Burgess, Laura Stevens, Wen Zhang, and Louise Peck. Long-chain polyunsaturated fatty acids in children with attention-deficit hyperactivity disorder. Am J Clin Nutr 2000 71: 327-330.

14. Cunnane SC, Francescutti V, Brenna JT, Crawford MA. Breast-fed infants achieve a higher rate of brain and whole body docosahexaenoate accumulations than formula-fed infants not consuming dietary docosahexaenoate. Lipids 2000 Jan;35(1):105-11.

15. Artemis P Simopoulos. Essential fatty acids in health and chronic disease. Am J Clin Nutr 1999 70: 560-569.

Fats have fallen out of favor lately. On the one hand, this is certainly true - fatty foods are very high in calories, and in the pursuit of harmony, every calorie eaten is under strict accounting. But do not forget that the complete rejection of this class of nutrients can bring serious health problems. After all, they include many components necessary for the normal functioning of our body: for example, polyunsaturated fatty acids.

If you recall the school course of organic chemistry, then it turns out that fats are compounds of glycerol and fatty acids.

Fatty acids are organic substances in the molecules of which the -COOH fragment, which is responsible for acidic properties, is connected to carbon atoms that are sequentially linked to each other. A few more hydrogens are attached to each carbon atom, as a result, the design looks something like this:

CH3-(CH2-CH2)n-COOH

It happens that in some acids "carbons" are connected to each other not by 1, but by 2 bonds:

CH3-(CH=CH)n-COOH

Such acids are called unsaturated.

If there are many carbon atoms in the compound, linked to each other by 2 bonds, then such acids are called polyunsaturated, from the ancient Greek “polis”, which means a lot.

The latter, in turn, are further divided into several groups, namely:

• omega 9;
• omega 6;
• omega-3 polyunsaturated acids.

Which of them an unsaturated acid belongs to is determined by which carbon atom, if starting from the non-acidic end of the molecule (CH3-), will have the first 2-nd bond.

By the way, our body produces omega-9 acids on its own, but we get representatives of 2 other groups only from food.

Why are polyunsaturated fatty acids needed?

These compounds are a necessary component for the shell of all animal cells - the so-called cell membrane. Moreover, the more complex the activity of the cell, the higher the amount of polyunsaturated fatty acids in its shell. For example, in the cell membrane of the retina of our eye, there are almost 20% of such acids, and in the shell of subcutaneous fat cells, their content is less than 1%.

In addition to the building function, these substances are needed for the biosynthesis of endohormones - substances that affect the activity of the particular cell in which, so to speak, “local hormones” were formed. I would like to talk about them in more detail, since these compounds are responsible for many processes occurring in our body.

So, endohormones control such things as the onset or disappearance of pain and inflammation, and also affect the ability of blood to clot. They are formed, as mentioned above, from the acids already familiar to us, which are contained in the cell membrane. Moreover, from different groups, hormones are created designed to solve various problems. So, from omega-6 acids, substances are produced that are responsible for an adequate response of the human body to damaging environmental factors. Such endohormones increase blood clotting, which prevents a large loss of it during injuries, and also cause inflammation and pain - reactions that are unpleasant, but necessary for survival. However, if there is an excess of these substances, then the process gets out of control: the blood becomes too viscous, pressure rises, blood clots form in the vessels, the risk of heart attack and stroke increases, and allergic reactions increase.

Endohormones derived from omega-3 polyunsaturated acids have the opposite effect: they reduce inflammatory reactions, thin the blood, and relieve pain. Moreover, the higher the concentration of omega-3 acids in the body, the less hormones are synthesized from omega-6 acids. However, it is still not worth completely abandoning the latter - after all, in this case, hypotension, poor blood clotting and a drop in local blood are provided. Ideally, if the diet for 4 parts of omega-6 will be 1 part of omega-3 fatty acids.

Foods rich in polyunsaturated fatty acids

POLYUNSATURATED FATTY ACIDS OMEGA-3 AND OMEGA-6

IN HUMAN NUTRITION

T.V. Vasilkova, Candidate of Medical Sciences, Associate Professor of the Department of Biochemistry

Polyunsaturated fatty acids (PUFAs), which are among the essential nutritional factors, have become the subject of considerable attention of researchers and doctors both in our country and abroad. Over the past decades, data have been accumulated indicating the important role of these compounds in normal development and maintaining a balance between physiological and pathological processes in the body.

About 70 fatty acids are found in human tissues. Fatty acids are divided into two large groups: saturated and unsaturated. Unsaturated fatty acids have one (monounsaturated) or several (polyunsaturated) double bonds. Depending on the position of the double bond in relation to the last carbon atom of the methyl group of unsaturated fatty acids, denoted by the Greek letter ω (sometimes the Latin letter n), several main families of unsaturated fatty acids are distinguished: omega -9, omega -6 and omega -3 (table). A person can synthesize PUFAs of the oleic acid series (ω-9) by combining the reactions of elongation (lengthening) and desaturation (formation of unsaturated bonds). For example, from omega-9 oleic acid (C 18:1), animal cells can synthesize 5,8,11-eicosatrienoic acid (C 20: 3, ω-9). With a lack of essential PUFAs, the synthesis of this eicosatrienoic acid increases and its content in tissues increases. Among unsaturated fatty acids, omega-3 and omega-6 fatty acids cannot be synthesized in the body due to the lack of an enzyme system that could catalyze the formation of a double bond at the ω-6 position or any other position close to the ω-terminus. So, they cannot be synthesized in the body linoleic acid and α-linolenic acid(ALK). They are essential fatty acids and must be obtained from food.

There are two classes of essential (essential) polyunsaturated fatty acids: omega-3 and omega-6.

to polyunsaturated fatty acids ω -6 includes linoleic acid (C 18: 2, ω-6), which in the body can turn into arachidonic acid (C 20: 4, ω-6). Arachidonic acid(AA) is indispensable in the body only with a lack of linoleic acid.

The most important polyunsaturated fatty acids of the class ω -3 are alpha linolenic acid(C 18:3, ω-3), from which long-chain PUFAs ω-3 can be synthesized in cells: eicosapentaenoic acid(S 20:5, ω-3) and docosahexaenoic acid(C 22:6 , ω-3) with about 5% efficiency in men and slightly higher efficiency in women. The ability to synthesize docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in the body is very limited, so they must come from exogenous sources. With aging of the body and some diseases, the ability to synthesize DHA and EPA is completely lost. In addition, it should be taken into account that the reactions of chain elongation and desaturation of ω-3 and ω-6 fatty acids are catalyzed by the same enzymes, and fatty acids compete for enzymes in these reactions. Therefore, an excess of fatty acids of one family, such as arachidonic acid (C 20: 4 , ω-6), will inhibit the synthesis of the corresponding acid of another family, such as eicosapentaenoic acid (C 20: 5 , ω-3). This effect highlights the importance of a balanced composition of omega-3 and omega-6 PUFAs in the diet. Thus, accumulation of long-chain EPA and DHA in tissues is most efficient when they come directly from food, or when competing amounts of omega-6 analogs are low.

Natural sources of PUFAs are vegetable oils from the ovary of wheat, flax seed, camelina oil, mustard oil, sunflower oil, soybeans, peanuts, as well as walnuts, almonds, sunflower seeds, fish oil and fish of fatty and semi-fat species (salmon, mackerel, herring, sardines, mackerel, trout, tuna and others), cod liver and shellfish.

Fig 1. Dietary sources of essential polyunsaturated fatty acids

The main dietary source of omega-6 PUFAs are vegetable oils. Omega-6 fatty acids are synthesized by most plants that grow on land. The main dietary source of omega-3 PUFAs are fatty varieties of cold-water fish and fish oil, as well as vegetable oils such as linseed, perilla, soybean and rapeseed.

The attention of researchers to the fatty acid composition of fat consumed with food was first attracted in the mid-70s of the last century, when epidemiological studies showed a low prevalence of diseases associated with atherosclerosis in the Greenland Eskimos and their mortality from myocardial infarction was 10 times lower than in Denmark and North America, despite the fact that the consumption of fat and cholesterol in all these populations was equally high. The difference was in the composition of fatty acids. In Danes, the consumption of saturated fatty acids and omega-6 PUFAs was 2 times higher than that of the Eskimos. The Eskimos consumed 5-10 times more long-chain omega-3 PUFAs: EPA and DHA. Further experimental and clinical studies have confirmed anti-atherogenic effect of omega-3 PUFAs. It has been established that omega-3 PUFAs reduce the content of atherogenic lipoproteins (low and very low density lipoproteins) in the blood. Confirmed cardioprotective and antiarrhythmic action(Free EPA and DHA in heart cell membranes inhibit ion channels) Omega-3 PUFAs. Recently, studies have been carried out showing immunoprotective action omega-3 fatty acids. Recent scientific discoveries have found that omega-3 fatty acids can block tumor growth.

Omega-3 PUFAs have been known to be essential for normal growth since the 1930s. DHA along with EPA - food components normal development of children and longevity. A growing organism needs a plastic material for its growth and development and is most sensitive to a deficiency of polyunsaturated fatty acids. PUFAs are part of structural lipids, including phospholipids of cell membranes. They are regulators of the phase state of cell membranes. An increase in omega-3 PUFAs in biomembranes leads to an increase in their liquidity, reduces membrane viscosity and improves the functions of integral proteins. With age, the content of omega-3 PUFAs in cell membranes decreases. E Icosapentaenoic acid is a lipid component of most tissues. Docosahexaenoic acid is an important component of the membranes of CNS cells, accumulates in synapses, photoreceptors, spermatozoa and is vital for their functions. Conducted scientific studies have confirmed that omega-3 PUFAs are required for the normal functioning of the brain.

In addition to their structural function, PUFAs such as arachidonic acid and eicosapentaenoic acid are precursors to a group of highly active substances called eicosanoids (Fig. 2). These include prostaglandins, prostacyclins, thromboxanes, and leukotrienes, which are widely distributed in body tissues. The ratio of PUFAs omega-3 and omega-6 directly affects the type of eicosanoids synthesized by the body.

Polyunsaturated fatty acids

General formula: CH 3 - (CH 2) m - (CH \u003d CH- (CH 2) x (CH 2) n-COOH

Eicosanoids synthesized from omega-6 PUFAs, mainly arachidonic acid, are the so-called second series of prostanoids: prostaglandins (PGI 2, PGD 2, PGE 2, PGF 2), thromboxane A 2 (TXA 2), as well as fourth series leukotrienes. They have pro-inflammatory, vasoconstrictor and proaggregant properties, providing protective reactions of the body - inflammation and stopping bleeding. Eicosanoids synthesized from omega-3 PUFAs, mainly from eicosapentaenoic acid (the third series of prostaglandins and the fifth series of leukotrienes), are characterized by anti-inflammatory and antithrombotic effects in contrast to the biological effects of arachidonic acid metabolites. Thus, EPA metabolites are preferred in humans under pathological conditions. The simplest way to reduce the synthesis of omega-6 eicosanoids was found to be the consumption of more omega-3 PUFAs. Dietary administration of EPA and DHA blocks the synthesis of eicosanoids from both arachidonic acid and endogenous eicosatrienoic acid (ω9). At the same time, if AA is completely excluded from the diet of a healthy person, then this will only bring a negative result, since EPA metabolites do not fully perform the functions that AA metabolites perform. This is confirmed by the results of epidemiological studies: residents of coastal areas who eat exclusively seafood do not suffer from atherosclerosis, but they have increased bleeding and low blood pressure.

For a healthy person, it is enough to follow proper nutrition. The industrial processing of fats and oils has greatly reduced the content of essential fatty acids in our diet. In the diet, the share of essential fatty acids should account for (in terms of calories) at least 1-2% of the total calorie requirement of the body. The optimal ratio of ω-3:ω-6 fatty acids in food is 1:4. The Russian Ministry of Health recommends 1 g of ALA/EPA/DHA per day for adequate intake. The minimum daily human need for linoleic acid is 2-6 g, but this need increases in proportion to the proportion of saturated fats entering the body. One way to get adequate amounts of EPA and DHA is to eat oily marine fish. For example, a typical serving of fish (85 g) may contain 0.2 to 1.8 g EPA/DHA. American experts recommend eating two servings of fish per week.

In certain pathologies, it is important to increase the intake of ω-3 fatty acids, which can be in the form of dietary supplements or drugs.

Rice. 3. Omega-3 polyunsaturated fatty acids in capsules

To get the maximum benefit from PUFAs, you should follow the storage rules (protection from atmospheric oxygen and other oxidizing agents, from direct sunlight) and use them in the required quantities. Consumption of excessive amounts of PUFAs can lead to disruption of the prooxidant-antioxidant homeostasis of the body. All PUFAs are subject to the process of overoxidation, and with a lack of natural antioxidants, this leads to the formation of free radicals with shifts towards increased atherogenicity and carcinogenesis. A necessary condition is the presence of natural antioxidants in physiological doses in preparations containing PUFAs. For example, vitamin E, which is found in fish and seafood, serves as such an antioxidant.

Polyunsaturated fatty acids have double bonds in their molecular structure. Aliphatic acids, in which double bonds are localized at the 3rd carbon atom, from the side of the methyl end, are called polyunsaturated fatty acids. The most studied fatty acids of this class are α-linoleic, eicosahexaenoic, clupadonic, eicosapentaenoic and docosapentaenoic acids. We can say that these are the building material that is necessary for the construction of cell membranes. Most scientists believe that more than 80 percent of the population of our country consumes insufficient polyunsaturated fatty acids. The population of many CIS countries consumes a significant amount of refined (synthetic) fats, while natural fats take second place. This leads to the fact that our body is simply not able to absorb the transformed fats, moreover, they have a carcinogenic effect.

ɷ-3 fatty acids cannot be formed in the body. They come to us only with food, and they are also called essential or essential fatty acids. Greenland is a scientific center for the study of the biological role of these acids. It has been scientifically proven that the Eskimos who live in this area have low levels of cholesterol in their blood. They rarely register myocardial infarction, vascular atherosclerosis and arterial hypertension. The researchers found that the daily diet of local residents includes about 16 grams of fish oil. This suggests that it is he who should have a beneficial effect on the heart and blood vessels.

Polyunsaturated fats are of great importance for human health. Regular use of ω-3 acids prevents the development of various pathologies of blood vessels, the heart, the digestive tract, has a positive effect on the function of spermatozoa, optimizes lipid metabolism, blood pressure, helps with migraines, accelerates in fish products, vegetable linen), vegetables (spinach, cabbage, beans, nuts) are very high in essential fatty acids. Another option to replenish their deficiency is to take various biological supplements and pharmaceuticals. When using them, you can fully provide your body with these extremely necessary compounds. In the pharmaceutical market, the most popular additives are: "Katranol +", "Eikonol", "Polyen", "Poseidonol", "Energomax Reishi Omega-3", etc.

Polyunsaturated fatty acids are an integral part of phospholipids. These biocompounds exhibit antitumor properties. Therefore, their deficiency leads to various anomalies in the structure of cell membranes. Polyunsaturated fatty acids are used to prevent neoplasms in the body. You should not abuse such drugs; before starting the course, you should consult with specialists, since there are a number of contraindications regarding their use. Polyunsaturated fatty acids are not recommended for people with allergic reactions to fish products, liver dysfunction, children under seven years of age. Side effects include: disturbances in the functioning of the digestive system (constipation, diarrhea, nausea, vomiting). Taste in the mouth can be easily eliminated with bread, fruit, pickles, and juices. People taking drugs containing polyunsaturated fatty acids claim that their health has improved, the functioning of the digestive system has normalized, and, according to the results of laboratory tests, the concentration of cholesterol in the blood has decreased.

Polyunsaturated fatty acids. Many of us think: “Why should I know anything about them?” But this is the wrong question. What rules in this context should we know?

Fatty acids useful for the human body

Without polyunsaturated fatty acids (or PUFAs for short), our body will not be able to "work" effectively. However, these substances are found only in products consumed by humans. They have another name: Omega number three and six. These acids are not synthesized by humans, and therefore each of us must carefully monitor our diet and control their intake into the body, and in sufficient quantities. There is also a set of vitamins F, which includes polyunsaturated fatty acids in full.

What joy do we get from these fats? Experts, based on numerous studies, are sure that it is colossal: these elements are involved in the metabolic process of our body and, very importantly, they “work” at the cellular level. Polyunsaturated fats provide full protection to cells, prolong their life and include mechanisms to preserve the genetic information that they contain. So eat foods rich in Omega number three to six - and premature aging will not threaten you. In addition, these acids optimize the metabolism of fatty elements and regulate the life of bacteria necessary for the human body.

The unique “abilities” of the above healthy fats do not end there. Firstly, despite the fact that these acids are not synthesized by our body, they themselves stimulate very important processes: for example, Omega types 3 and 6 are involved in the formation of hormone-like substances that help prevent internal inflammation and lower blood pressure. Secondly, polyunsaturated fatty acids balance the level of cholesterol in our body, which positively affects the state of blood vessels and heart muscle.

Where to find healthy fats?

In total, there are 5 essential polyunsaturated types of fats - these are the following acids:

• linolenic,
• arachidonic,
• eicosapentaenoic,
• docosahexaenoic,
• linoleic.

They are present in many products. But there are also winners in their content. The main supplier of Omega three and six to our body are vegetable oils, especially soy, walnut and linseed. These substances can be found in other oils, as well as in soybeans, avocados, almonds and peanuts. All of the above products in one way or another should be included in your daily diet.

Do not forget that the greatest benefit from vegetables will be only if you consume them fresh. It must be remembered: useful substances are destroyed during refining or heat treatment. This occurs as a result of the oxidation of the substance. Also, this process “starts” when interacting with air. Therefore (with regard to vegetable oils) they are best consumed unrefined and stored in closed containers (bottles). But polyunsaturated fats are not recommended for frying. As a result of heat treatment, after reaching a certain temperature, carcinogenic substances are formed that are very harmful to the human body.

Be careful with linseed oil. It has very high oxidizing properties. Such oil after opening should be stored only in the refrigerator and no more than 30 days. Use flaxseeds in your menu. It is enough to add 1 teaspoon of this product to food daily in ground form.

The need for polyunsaturated fats is covered by many people through the use of fish oil purchased in pharmacies. This is not the best option. Foods that contain beneficial substances such as Omega-3 and Omega-6 are more effective. They are more easily absorbed by our body, and their taste is much richer than that of fish oil capsules. It is much more pleasant to eat cauliflower and Chinese cabbage, broccoli, spinach, beans, salads seasoned with various oils, or juicy melon - they are all rich in polyunsaturated fats necessary for the human body.

Omega-3 and Omega-6: intake per day

Measure is needed in everything, especially for the human body. It needs many useful substances, but their effectiveness is maximum if a certain norm of their consumption and an appropriate balance are observed. It is a mistake to think that if you eat foods rich in Omega-3 and Omega-6 with "fanaticism", your body will be "delighted". On the contrary, an excess of these fatty acids will overload your liver and pancreas. It makes no sense to experience them, just as you should not ignore the benefits of polyunsaturated fats. You will feel their deficiency immediately. It is better to observe the principle of balanced and reasonable consumption.

Our body needs to receive approximately 2.5 g of fatty acids per day, which is almost 2 tablespoons. Naturally, this amount applies not only to oil, but also to all types of products that contain these substances. So, be sure to eat foods that contain Omega-3 and Omega-6, do not overdo them, and nature will give you health, wellness, high energy and long life in return.