Introduction
Essential fatty acids or AGE * (Italian acronym) are very important nutrients.
On the other hand, the large amount of information, and the high speed with which scientific updates are disclosed, create havoc among professionals (supporters and skeptics) and confusion in public opinion.
The main information concerning essential fatty acids will be grouped below.
*In English. essential fatty acids are called Essential Fatty Acid or are indicated with the acronym EFAs.
What are?
Chemistry and Physics of Essential Fatty Acids
Also known as vitamin F, from the chemical point of view the essential fatty acids belong to the group of lipids (or fats).
Chemistry recall
Fatty acids (acronym AG or FA) are classified into three groups - saturated, monounsaturated and polyunsaturated - depending on the presence of one or more double bonds along their carbon chain.
This denotes some specific chemical-physical properties; the most interesting are:
- Liquid / slightly viscous consistency at low temperatures.
- Instability and susceptibility to oxidation, free radicals, light and heat, which require specific conservation needs
Essentials: Why?
These fatty acids are considered "essential" because the body is not able to produce them independently.
Any nutrient that the body has to bring in from the surrounding environment is essential.
Simply put, the only source of supply of essential substances is food.
Foods can contain essential nutrients "in whole" or in the form of precursors, that is, substrates to be used as "raw material" to derive these essential factors.
Did you know that ...
Essential nutrients are NOT the same for all living organisms. For example, an amino acid called taurine, which is ordinary for human beings, is essential for the cat. Furthermore, the essentiality can change according to age, as happens in humans for certain amino acids that are essential only at a young age.
How Many Are Essential Fatty Acids?
The "really" essential fatty acids are two:
- Linoleic acid (from the group ω6 or n-6 or omega 6)
- Α-linolenic acid (alpha, of the group ω3 or n-3 or omega 3).
With these two nutrients available, the body is able to obtain other compounds, with specific or metabolically different functions.
As it is easily deducible, the derivatives belong to the group of omega 3 if they come from the alpha linolenic acid and from the group of omega 6 if they come from the linoleic acid group.
The research institutes have established the recommended ration (quantity to be taken with the diet) unifying all the exponents of the single groups; it is a mere practical simplification, but the lack or excess of essential fatty acids does not only depend on the quantity, but also on the chemical typology of these nutrients taken with food.
For example, arachidonic acid (20: 4 ω6) is considered an essential fatty acid only in the absence of its precursor or linoleic acid (from which it can be formed thanks to the elongation and desaturation of the carbon chain).
| Main derivatives of Alpha Linoleic Acid omega 3 | Main derivatives of Linoleic Acid omega 6 |
| Docosahexaenoic acid or DHA (22: 6 ω3) Eicosapentaenoic acid or EPA (20: 5 ω3) | Gamma linolenic acid or GLA (18: 3 ω6) Di-gamma-linolenic acid or DGLA (20: 3 ω6) Arachidonic acid or AA (20: 4 ω6) |
Functions
What are the functions of essential fatty acids?
The main function of fatty acids is caloric.
They supply energy in most human cells (through the β-oxidation of mitochondria), especially the muscle cells, which draw 9 kilocalories (kcal) per gram.
With regard to essential fatty acids, on the other hand, this function is only marginal and acquires importance only in case of excessive intake with the diet.
The tasks of these molecules are very different; in fact, they play a fundamental role in many fabrics, for example:
- They participate in the constitution of cell membranes.
- They allow the synthesis of some substances called bioregulatory eicosanoids (or "superhormones") involved in the modulation of important cellular reactions such as inflammation.
- Especially in pathological conditions, they favor the restoration of metabolic parameters such as blood pressure, cholesterolemia, triglyceridemia and damage caused by hyperglycemia, etc.
- As a result, they protect against atherosclerosis, thrombosis and embolisms that trigger inauspicious events of a vascular nature (cardiac, cerebral ischemia, etc.).
- They support cognitive function and protect against degeneration of the nervous system.
- They guarantee the maintenance of the visual function.
- They can act positively on depression *. They exert a positive stimulus on the embryonic development and growth of the child.
The role of essential fatty acids in the body differs according to the family they belong to.
Mode aside, essential fatty acids are considered fundamental for the human diet and for combating cardiovascular diseases. Some functions are synergistic but, in many ways, certain omega 3 and omega 6 carry out different and almost opposite activities.
These effects are mediated by the eicosanoids of which they are precursors; let's see some of them.
Did you know that ... although they are objectively beneficial to health, the studies carried out on essential fatty acids do not always lead to the same results?
The metabolic impact may be partially different, in particular as regards the cholesterolemia profile.
Main functions of Omega 6
- They reduce the concentration of cholesterol in the blood, lowering above all the "bad" fraction (LDL), but do not have a decisive impact on the good one (HDL).
- They have a low efficacy in reducing plasma triglyceride levels (modest hypotriglyceridemic action).
- If present in excess of omega 3, it is possible that omega 6 will become responsible for a series of negative effects that can be observed in vitro. Being precursors of good eicosanoids, but also of some bad eicosanoids, they could increase allergic, inflammatory reactions, blood pressure, platelet aggregation and consequently cardiovascular risk. However, more recent evidence seems to deny these hypotheses, stressing the PREVALENCE of the anti-inflammatory effects in vivo.
Main functions of Omega 3
- Lower plasma triglyceride levels, interfering with their incorporation into the VLDL at the liver level.
- They have a low effectiveness in reducing total cholesterol levels in the blood (low cholesterol-lowering action).
- The concentration of HDL cholesterol may slightly increase.
- They are "good" eicosanoid precursors that decrease platelet aggregation, increasing blood flow and significantly reducing the risk of coronary heart disease.
- The omega 3s therefore have an antiatherogenic, anti-inflammatory and antithrombotic action.
How many do you take?
The need for essential fatty acids is not the same for everyone.
The Italian Society of Human Nutrition (SINU), with the latest publication of Reference Levels of Nutrients and Energy (LARN), emphasizes the importance of omega 3 and focuses more on the recommendation to take the right amount.
More Omega 3 in Children
The values do not differ from those previously published in 1996. However, greater attention is paid to the need for omega 3 in younger people.
In particular, especially for infants and children, it is recommended to introduce 0.5-2% of the energy in omega 3, of which at least 250 mg / day in the form of EPA and DHA + other 100 mg / day of DHA .
These values seem sufficient to compensate for the needs of this particular population group, also in relation to a possible influence on neurological and cognitive development.
In all, essential fatty acids must constitute 5-10% of total calories, of which 4-8% in omega 6 and 0.5-2.0% in omega 3.
Adults and Elderly
For adults and the elderly, on the other hand, the recommendations to introduce only 250 mg of EPA and DHA apply. Also in this case the essential fatty acids constitute 5-10% of the total calories (4-8% in omega 6 and 0.5-2.0% in omega 3).
Pregnancy and breastfeeding
In pregnancy and lactation it is advisable to add 250 to 200 mg of EPA and DHA another 100-200 mg of DHA.
Again, essential fatty acids should make up 5-10% of total calories, of which 4-8% in omega 6 and 0.5-2.0% in omega 3.
| LARN for Essential Fatty Acids | |||
| Grassi | RE Reference interval for nutrient intake | AI Adequate intake | |
| INFANTS | Total PUFA | 5-10% En | EPA-DHA 250 mg + DHA 100 mg |
| omega 6 | 4-8% En | ||
| Omega 3 | 0.5-2.0% En | ||
| CHILDREN UP TO 2 YEARS | Total PUFA | 5-10% En | EPA-DHA 250 mg DHA 100 mg |
| omega 6 | 4-8% En | ||
| Omega 3 | 0.5-2.0% En | ||
| CHILDREN AND ADOLESCENTS OVER 2 YEARS | Total PUFA | 5-10% En | EPA-DHA 250 mg |
| omega 6 | 4-8% En | ||
| Omega 3 | 0.5-2.0% En | ||
| ADULTS AND ELDERLY | Total PUFA | 5-10% En | EPA-DHA 250 mg |
| omega 6 | 4-8% En | ||
| Omega 3 | 0.5-2.0% En | ||
| PREGNANCY AND BREASTFEEDING | Total PUFA | 5-10% En | EPA-DHA 250 mg + DHA 100-200 mg |
| omega 6 | 4-8% En | ||
| Omega 3 | 0.5-2.0% En | ||
L egenda:
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Synthesis DHA and EPA
Among the various omega 3 derivatives originating from the metabolism of alpha linolenic acid, the most active and important are eicosapentaenoic acid or EPA (20: 5) and docosahexaenoic acid or DHA (22: 6).
This transformation is mediated by an enzyme called Δ-6-desaturase, whose catalytic activity decreases with aging, in case of alcoholism, hypoproteic diet, hyperglycemia and treatment with glucocorticoid drugs (cortisone).
For this reason, even if the food sources of alpha-linolenic acid are very important, it is good to also evaluate the percentage content of EPA and DHA.
Too many Omega 6
The reasons are different.
We have already specified that an excess of omega 6, absolute or proportional with respect to omega 3, is not advisable, due to their function (albeit partial) of increasing inflammatory eicosanoids.
Furthermore, an omega 3 fatty acid cannot be transformed into an omega 6 fatty acid, and vice versa; however, linoleic acid and alpha linolenic exploit the same enzyme system to originate the derivatives of the respective families. Due to this competition, excessive intake of omega 6 interferes with the formation of omega 3, and vice versa.
In itself, omega 6s are not harmful to human health but, even though they perform many essential and positive functions (first of all the reduction of cardiovascular risk), they can become so if consumed in excess compared to omega-3.
Essential fatty acid ratio
Based on some retrospective anthropological hypotheses, the nutrition of our predecessors was characterized by a ratio between omega 3 and omega 6 of about 1: 1 .
| Populations | ω3: ω6 |
| Palaeolithic | 1: 1.3 |
| Greece before 1960 | 1: 1 or 1: 2 |
| United States 2000 | 1: 16.7 |
| United Kingdom and Northern Europe | 1:15 |
| Japan | 1: 4 |
| Italy | 1:13 |
Looking at the percentages suggested in the previous chapter (ω3 0.5-2.0% and ω6 4.0-8.0%), the ratio that the research institutions consider currently acceptable is between 1: 4 and 1: 8. Using the values obtained by crossing the extreme numbers of the aforementioned percentages, ratios of 1: 2 and 1:16 would be obtained.
In most foods, the presence of essential fatty acids is in favor of omega 6 compared to omega 3.
However in recent years, in the face of an increasingly poor diet of fish and rich in certain vegetable oils derived from the seeds, this relationship has become significantly unbalanced in favor of the omega 6.
According to some research, the average of the western population follows a diet with a ratio clearly higher than 1:10.
For the reasons we have described above, this could be a negative factor for our health; therefore, it would be advisable to pay more attention to this nutritional parameter.
This is the fundamental reason from which comes the recommendation to consume at least two or three weekly portions of fish, possibly blue and of small size (very large fish are considered "mercury tanks"), or to integrate with specific products based on of omega 3.
Excess
In the right ratio of omega 3 to omega 6, it is best not to overdo the total amount of essential fatty acids.
The scientific evidence does not allow to define in any case the maximum tolerable level of food intake.
To defend itself from the excess, the organism seems able to eliminate essential fatty acids by using them to produce energy.
However, it is believed that an excess of essential fatty acids or polyunsaturates in general can be linked to
- Increased oxidative stress
- Blood peroxidation
- Gastrointestinal symptoms and many others
- Alteration of blood coagulation
- Excess of eicosanoids (based on the type of excess fatty acid) etc.
NB . These circumstances are very difficult to achieve with nutrition and with a reasonable supplementation of essential fatty acids.
In the food
AGE wealth: How to evaluate it?
We begin by specifying that the words "Rich Foods of" and "Foods That Contain Predominantly" are quite different.
This clarification is very important as, as we will see later, several foods can be considered rich in both omega 6 and omega 3. Indeed! Almost all foods contain both omega 6 and omega 3.
On the other hand, omega 3s are almost always very scarce compared to omega 6s and are more difficult to take in the right quantities.
This means that the " foods rich in omega 3 " are not necessarily " foods that contain predominantly omega 3 ". On the contrary, several foods considered rich in omega 3 possess a very high level of omega 6.
It can be deduced that most people take large quantities of omega 6 in an attempt to increase the introduction of omega 3.
Also for this reason, foods with a prevalence of omega 3 (especially those rich in the most metabolically active chains) are considered of great nutritional value.
Furthermore, by carefully observing the compositional detail of fatty acids, we note that the important characteristics to be evaluated are many:
- Total quantity of fatty acids
- Prevalence of saturated or unsaturated ones
- Of those unsaturated, prevalence between monounsaturated and polyunsaturated
- Compared to polyunsaturated fats, the importance of essential fatty acids
- In the essentials, quantities of omega 3 and omega 6 (as will be discussed in another article, the relationship between them also plays a decisive role)
- Within the omega 3 and omega 6 groups, prevalence of the essential chains or of the more or differently active metabolically derivatives etc.
| Examples of foods rich in Alpha Linolenic Acid Omega 3 | Examples of Foods Rich in Linoleic Acid Omega 6 |
| Blue fish, cod liver oil, crustaceans and molluscs, krill and krill oil, algae and algae oil etc. | Peanuts and peanut oil, pistachios, almonds, walnuts, wheat germ and oil, sunflower seeds and oil, sesame and oil, rice germ and oil, etc. |
Did you know that ... fish rich in omega 3 have fatty meats and live in cold waters, such as salmon, sardines, mackerel, bonito, herring, tuna belly etc.
Omega 3 essential fatty acids are more abundant in fish caught than in farmed ones. While the latter are often "forced" in growth with high-calorie feed, but poor in "intact" omega-3, wild fish feed on organisms naturally rich in EPA and DHA.
Although they do not represent an excellent nutritional source of essential fatty acids (especially omega 3), the same is true for animal meat, eggs and milk, in which the presence of AGE appears to be lower in intensive breeding products.
NB . Recently various compositional changes have been applied in the formulation of the feed, to the advantage of the composition of the fish and of the farmed meat.
Content of Omega 3 and Omega 6 in the Most Rich Foods
| FOOD (100 g) | ω-3 | ω-6 | ω-6: ω-3 | |||
| DHA (g) | EPA (g) | LNA (g) * | totals (g) | totals (g) | - | |
| Salmon oil | 18.232 | 13, 023 | 1, 061 | 35.311 | 1, 543 | 0.04: 1 |
| Liver oil of cod | 10, 968 | 6, 898 | 0, 935 | 19.736 | 0, 935 | 0.05: 1 |
| Sardine oil | 10.656 | 10, 137 | 1, 327 | 24.093 | 2, 014 | 0.08: 1 |
| Caviar | 3, 801 | 2, 741 | 0, 017 | 6, 789 | 0.081 | 0.01: 1 |
| Mackerel | 1, 401 | 0, 898 | 0 | 2, 670 | 0.219 | 0.08: 1 |
| Coho salmon (wild) | 0.656 | 0, 429 | 0, 157 | 1, 474 | 0.206 | 0.14: 1 |
| Coho salmon (breeding) | 0.821 | 0, 385 | 0.075 | 1, 281 | 0.349 | 0.27: 1 |
| Anchovy or alice | 0, 911 | 0.538 | 0 | 1, 478 | 0, 097 | 0.07: 1 |
| Tuna | 0, 890 | 0.283 | 0 | 1, 298 | 0.053 | 0.04: 1 |
| Herring | 0.862 | 0.709 | 0, 103 | 1, 729 | 0, 130 | 0.08: 1 |
| Flax seed | 0 | 0 | 22.813 | 22.813 | 5, 911 | 0.26: 1 |
| Linseed oil | 0 | 0 | 53.304 | 53.304 | 12, 701 | 0.24: 1 |
| Walnut oil | 0 | 0 | 10, 400 | 10, 040 | 52.890 | 5.27: 1 |
| Dried walnuts | 0 | 0 | 8, 718 | 8, 718 | 33.717 | 3.87: 1 |
| Dried almonds | 0 | 0 | 0 | 0 | 12.648 | - |
| peanuts | 0 | 0 | 0, 170 | 0, 170 | 10.535 | 61.97: 1 |
| Dry salted pistachios | 0 | 0 | 0, 263 | 0, 263 | 13.636 | 51.85: 1 |
| Soy lecithin | 0 | 0 | 5, 135 | 5, 135 | 40.178 | 7.82: 1 |
| Olive oil | 0 | 0 | 0761 | 0.761 | 9, 763 | 12.83: 1 |
| * LNA = undifferentiated alpha-linolenic acid SOURCE: "essential fatty acids in food" has been prepared based on data provided by the US Department of Agriculture | ||||||
