Importance of polyunsaturated fatty acids in the human body

What an energy concentrate looks like

In human diet, fats are the most concentrated energy source, over twice as energy-rich as carbohydrates. They contain saturated and unsaturated fatty acids, vitamins soluble in them, and many other lipid compounds.

Energy concentrate through a magnifying glass

Fats are compounds of glycerol (a type of alcohol) and fatty acids. Regardless from whether these are animal fats or plant fats, they are a specific composition of various fatty acids. Their chemical construction is based on one principle: all fatty acids are constructed of carbon (C) and hydrogen (H) molecules, which bind with one or two oxygen molecules (O) in order to finally become an organic acid called carboxylic acid (carboxylic group COOH).

Fatty acids present in natural fats always have an even number of carbon atoms. Carbon atoms are usually connected with each other like pearls in a necklace.

Fats are saturated or unsaturated, but with what?

In the discussion on the biological importance of food for humans, a great role is played by two main groups of fatty acids, i.e. saturated and unsaturated fatty acids.

When hydrogen atoms take all bindings in the carbon molecules chain, an acid is saturated. For example, butyric acid:


However, when two carbon atoms have double bonds (=), each of them must bind one hydrogen atom less. We call such fatty acids unsaturated fatty acids, e.g. oleic acid (18:1):


There are also polyunsaturated fatty acids, which have at least two double bonds, e.g. linolic acid (C18:2, Ω-6):


How to look for diminutives for acid names?

Names of fatty acids always include, at the beginning, the number of C carbon atoms in the chain contained in the acid.

In the above example (linolic acid), there are 18 C atoms in total. In this type of symbols, the number of double bonds is provided after the colon. In the above example, there are two bindings; therefore, the short description is as follows: 18:2. Information on where the double bonds located in the chain (counting from the left), is called the omega position (Ω) or, in new terminology, is marked with „n” (C18:2, Ω-6 lub C18:2, n-6).

About omnipotent alpha and omega and why acids race

Before, we discussed Ω-6 family. Below, we present the precursor of all fatty acids belonging to the Ω-3 group with the full name of alpha (α) linolenic acid. It has three unsaturated bonds:

α - linolenic acid (C18:3 Ω-3)

In metabolic processes, linolic acid (Ω-6) and alpha-linolenic acid (Ω-3) compete for the same digestive enzymes. Therefore, excessive amounts of linolic acid in food inhibit the synthesis of EPA and DHA acids (fatty acids formed in the transformation of linolic acid) and increase the synthesis of arachidonic acid (AA).

This may disturb the balance of physioSuitable supply of acids from the Ω-3 family, in particular EPA and DHA, in food prevents excessive production of arachidonic acid in the body and inhibits, at the same time, transformations leading to the formation of arachidonic acid (AA).

Polyunsaturated acids full of fatty benefits

Polyunsaturated fatty acids are essential for correct development of young organisms and for maintenance of good health by humans. These acids belong to Ω-6 and Ω-3 families.

Linolic acid (C18:2 Ω-6) is also counted among them as well as fatty acids with longer chains, formed from linolic acids in animal and human tissues, which also belong to the Ω-6 family:

  • dihomo-γ-linolenic acid (DHGLA) (C20:3, Ω -6)
  • arachidonic acid (AA) (C20:4, Ω-6)
  • α-linolenic acid (C18:3 Ω-3)

and which belong to the Ω-3 family:

  • eicosapentaenoic acid (EPA) (C20:5, Ω-3)
  • docosahexaenoic acid (DHA) (C22:6, Ω-3)

20-carbon acids are substrates for the synthesis of eicosanoids, which contain prostaglandins, prostacyclins, tromboxanes, leukotrienes, hydroxy- and epoxy- fatty acids, and lipoxins, which are essential in metabolism.

Eicosanoids – tissue hormones and their never-ending scope of responsibilities

Eicosanoids can be treated as the most external 1st class transmitters located most externally, which intensify or weaken the regulative activity of hormones and neuromediators on the cellular level. Substrates for the synthesis of eicosanoids are located in phospholipids in the cellular membrane.

In recent years, many facts have been determined which prove that eicosanoids have a very wide scope of activity.

They have a significant influence on the regulation of the activities of the cardiovascular system and oxygenation of tissues, and they have antiarrhytmic effect (reducing the risk of arrhytmia). They control the regulation of blood pressure, balance in blood coagulation and de-coagulation, and vascular stability. They regulate the contents of lipoproteins, in particular HDL, triglycerides, and specific proteins of lipoproteins.

They influence the adaptation of the body immunity to inflammatory processes, proliferation (regeneration and reproduction) of cells, activities of hormones and neuromediators, gene expression, and activities of many organs, such as brain, kidneys, lungs, and digestive tract, the feeling of pain, and many other physiological and biochemical processes.

Influential Ω-3 family

It has been determined that people who eat a lot sea products containing fatty acids from the Ω-3 family less frequently suffer from diseases characteristic for the population in the industrialized Western countries, called metabolic civilization diseases.

It has been indicated that in these people the incidence of atherosclerosis, myocardial ischaemia, breast carcinoma, colorectal cancer, intravascular clots, and asthma is smaller. It has also been proved that fish oil has a medicinal effect in the experimental cerebral haemorrhage, myocardial infarction, and psoriasis.

Many scientific data has been gathered which indicates that fatty acids from the Ω-3 family have a very beneficial effect on the blood circulation system. It has been determined that fish oils have a strong hypotensive effect (reduction of blood pressure); therefore, they should be recommended in arterial hypertension. They also reduce VLDL, triglycerids, and cholesterol levels in blood serum, in particular the levels of total cholesterol, and increase the HDL cholesterol levels at the same time.

Where can these families be found?

OilΩ-3 [%]Ω-6 [%]
safflower oil 0 77
sunflower oil 0 69
corn oil 1 61
soy oil 7 54
walnut oil 5 51
sesame seed oil 1 4
peanut oil 3 3
canola oil 10 22
linseed oil 57 16
olive oil 1 8

Stressing proportions

In the diet of our ancestors, the levels of omega-6 fatty acids were five times higher than these of omega-3 fatty acids.

At present, due to changes in the selection of foodstuffs and methods of food processing, these proportions have changed and they are as much as 24:1; it is, therefore, much more difficult to satisfy the body's demand for omega-3 fatty acids. This is made even worse by the fact that these are impermanent products which decompose during heating.

The total reduction of the consumption of omega-3 acids results in DHA deficits, what poses a risk to health, in particular mental health.

In their work published in "American Journal of Clinical Nutrition", dr Joseph R. Hibbein and dr Norman Salem from National Institute of Health suggest that the increased incidence of depression in the Northern America during the last century should be related to the constant reduction of DHA consumption.

The authors discovered this fact in 1984, during their research on the relationship between cholesterol-low diet and frequent depressions in people.

At that time, it was difficult to explain this phenomenon. Later research indicated that the diet of people living near the coast is full of fresh fat fish, such as salmon or mackerel. On the other hand, people living in the interior eat them rarely. It was also discovered that the incidence of stress increases as the distance from the coast grows.

The conclusion could only be as follows: if there is fat fish, which contains large amounts of omega-3 fatty acids, in the diet, the body deals with stress easier. Docosahexaenoic acid (DHA) can also be taken in the form of supplements, the best dose is 2-4 pills (250 mg each) a day.