Strange to say but facts are actually very important parts of our diet – no matter what kind of dietary habits we have. While eating too many fats is hazardous, some fats are essential for physiological functions and have highly beneficial health effects on several Western diseases. The beneficial effect of some of these fats was first shown in the Eskimo population, who consume a large amount of marine animal-derived fat, meanwhile the development of cardiovascular diseases – and death due to this reason – is extremely rare among them. Although the highest amount of these “beneficial fats” can be found in seafood, some plants, seeds and nuts also contain appraisable amount of these. The reason why we consider the inhabitants of Okinawa (Japan) one of the healthiest populations in history is that their diet is also extremely rich in these “beneficial fats”. But what are they exactly?
A little chemistry…
The major component of fats is the so-called fatty acid, a long chain composed of carbon atoms linked to hydrogen, with a special group at the beginning (carboxylic group) of the chain. A fatty acid can be either saturated or unsaturated. These terms refer to the number of hydrogen atoms in the molecule. A saturated fatty acid binds the maximum number of hydrogen atoms, while in unsaturated fatty acids the participating carb atoms cannot bind as many hydrogen atoms as their saturated fellows (and this is where their name derives from). The reason for the incomplete saturation is the presence of one (or more) double bond in between two carbon atoms. If there is a double bond in the structure, the carbon atoms are occupied to bind to each other strongly and don’t have enough space for hydrogen atoms. A commonly used manner to name unsaturated fatty acids is to count how far is the last double bond from the very end of the fatty acid. The last carbon atom in a fatty acid is called “omega” (no matter how long the carbon chain itself), so omega-3 fatty acid means, that the last double bond from the end of the fatty acid chain is 3 carbs away. Likewise, in omega-6 or omega-9 fatty acid the last double bond is 6-or 9-carbons away form the end.
And now some medicine
First of all, omega fatty acids are not only important due to their beneficial health effects, but also because we are not able to produce them in our body. This means that we have to rely on external sources of omegas, which makes them “essential” compounds (like vitamins, trace elements and those amino acids which we cannot synthesize, but still needed for our body to function).
The most important members of the omega-3 fatty acids are a-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) — all of them being essential for many physiological functions of ours. It is necessary to mention them separately, as the dietary sources of these are really different, and because the beneficial cardiovascular effects are attributed to EPA and DHA only. ALA is primarily present in plants (for example in flaxseed, chia seed and walnuts), while EPA and DHA are the animal-forms of omega-3 fatty acids, found mostly in sea-fish (e.g. mackerel, herring and salmon). The main food source of these fish are algae and phytoplankton, which are able to produce EPA and DHA from ALA, therefore the animals consuming them will be extremely rich in these fatty acids. Human body can also convert ALA into EPA and then to DHA through a multi-step biochemical reaction, however the rate of this conversion is inefficient, especially in those persons who got used to a typical fat-rich Western diet. Due to the inefficient conversion rate and to the fact that only EPA and DHA are beneficial for cardiovascular health, it would be recommended to eat them – and not only ALA. They were described to decrease the mortality of coronary disease and cardiac arrhythmia, ameliorate hypertension and hyperlipidemia. The currently updated recommendation of American Heart Association includes treatment of patients with prevalent coronary heart disease, or heart failure with omega-3 fatty acids to decrease mortality. Another notable group of effects of omega-3s are related to the development of central nervous system and to its functions. They were described to be beneficial in several psychiatric disorders, and to have a positive influence on mods and behavior.
Most important members of omega-6 fatty acids are linoleic acid and arachidonic acid, this latter being the most acknowledged omega-6 member as it serves a precursor for many bioactive lipids. These lipids serve in diverse physiological processes, for example in platelet and leukocyte activation, signaling of pain and inflammation, etc. Vegetable oils, nuts and seeds contain linoleic acid, which may then be converted into arachidonic acid within our body. Linoleic acid – along with the omega-3 a-linolenic acid – are the two major essential fatty acids cannot be produced at all in humans.
The primary omega-9 fatty acid is oleic acid. Since we are able to synthesize oleic acid by inserting a double bond into its saturated counterpart, it is not an essential fatty acid and we don’t have to rely on external sources. However, consuming oleic acid containing foods (olive oil and almonds) is still very healthy – it was shown to decrease cholesterol level, thus atherosclerosis.
What are the conclusions?
It is very important to keep in mind that whatever food we eat, it contains a mixture of fats, so it is not possible to intake only one of these. Keep in mind to check the fat composition of a certain food, and try to use those that are high in unsaturated and low in saturated fatty acids. Required supplementation might be dependent on the geographical region we live. While in the US and in the majority European countries the vegetable sources of unsaturated fatty acids might be easily ensured, the marine-sources of fatty acids are lack in most of the people. We should pay attention to adequate diet and fatty acid composition of our food, and supplement those omega fatty acids that our diet doesn’t contain in sufficient amount.
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