When we talk about a healthy and balanced diet we always talk about omega-6 and omega-3 and how important they are to maintain an ideal state of health and to protect us from various diseases. But what exactly do we mean with “omega-6” and “omega-3”? Why is it so important to have them in our diet? How are these fats beneficial to our health?
First of all, it is essential to understand that including fat in our diet is of great importance: fats, or lipids, represent a heterogeneous class of water-insoluble compounds that play important roles in different functions of our organism (plastic, energy regulation, absorption of fat-soluble vitamins). It is therefore clear that a diet that eliminates them completely cannot be considered a balanced diet as lipids should represent about 25-30% of total calories.
The basic structure of most of the body’s lipids is made up of fatty acids. Depending on the molecule and the type of fatty acids that make up the structure, fats acquire different characteristics and functions, which is why it is very important to learn about them.
Generally speaking, we could say that fatty acids are made up of a long linear series of carbon atoms held together by bonds that can be single or double.
Here it is possible to make the first fundamental distinction between saturated fatty acids and unsaturated fatty acids:
- Saturated fatty acids: the carbon chains of saturated fatty acids are held together only by single bonds. This characteristic gives stability to the fats that contain them which consequently have a higher melting point (i.e. they reach the liquid state at a higher temperature). These fatty acids are the basis of animal fats such as butter, but are also present in the plant world, a classic example being palm oil, coconut oil, and cocoa butter.
- Unsaturated fatty acids: their structure presents double bonds. This makes the structure of the fats less stable and more “fluid” (lower melting point). Indeed, unsaturated fatty acids are typical of “liquid” vegetable oils at room temperature such as olive oil and seed oils but they are also found in fish (cod liver oil).
In turn, unsaturated fatty acids can be divided according to the number of double bonds into monosaturated (a single double bond in the chain of carbon atoms) and poliunsaturated (more than one double bond); omega-3 and omega-6 fatty acids belong to the latter category.
Every time we eat, we take in a portion of fatty acids in the form of lipids of various kinds. These, once metabolized, perform specific functions within the body: structural function (phospholipids), energy (deposit triglycerides), hormonal (prostaglandins), etc.
Our body and our cells are able to synthesize most of the molecules and structures they need through metabolism, but for everything to work properly it is necessary to introduce in our diet some nutrients that we are not able to produce independently. These play fundamental roles in maintaining our state of health and their prolonged deficiency, or concentrated in certain stages of growth, can lead to quite serious consequences.
So-called essential fatty acids belong to this class of essential nutrients:
- Linoleic acid or AL: progenitor of the class of omega-6 fatty acids
- Alpha-linolenic acid or ALA: progenitor of the omega-3 class
From these precursors, through the metabolism, the body is able to synthesize the fatty acids of the omega-6 and omega-3 long-chain class such as arachidonic acid (AA) omega-6, eicosapentaenoic acid (EPA) omega-3, and decosahexaenoic (DHA) omega-3, which are characteristic of the animal world and are found in eggs, meat, and fish.
To understand how essential these nutrients are for our well-being, just think that the lack of essential fatty acids in infants causes slow growth, skin changes, and a reduction in calorie efficiency in the diet.
Omega-6 fatty acids perform important functions within the body:
- They are precursors of eicosanoids that regulate inflammatory processes (contributing to the normal functioning of the immune system) and they are also involved in glucose and lipid metabolism, in the regulation of blood pressure, in the contraction of smooth muscles and various other functions.
- Moreover, they are involved in the modulation of cellular signals,
- They are precursors of receptors that regulate the activity of some enzymes,
- And they are involved in blood clotting.
As for omega-3 fatty acids:
- They are involved in the maintenance and regulation of the fluidity of cell membranes (phospholipids),
- They are involved in processes that regulate vision and hormones, and
- They play an anti-inflammatory role.
- Moreover, they have an antihypertensive function associated with the prevention of some diseases affecting the cardiovascular system.
These two types of fats play opposite and complementary roles within the body (for example pro- and anti-inflammatory) and their balancing contributes to the maintenance of a normal state of health. Indeed, scientific evidence supports the idea that various conditions characteristic of our time (cardiovascular diseases, osteoporosis, chronic intestinal inflammatory diseases, etc.) are associated with an altered ratio in the intake of these fatty acids.
Several sources suggest that humans evolved following a diet with a ratio of omega-6 to omega-3 of around 1 while changes in eating habits over the past 100-150 years have brought this ratio to 15:1 or 20:1 in favor of omega-6 fatty acids. To date, the optimal ratio should be around 4:1 or 5:1. It is therefore evident that Western diets are deficient in omega-3 fatty acids, which by their action are now known to contribute to the normalization of blood cholesterol levels and consequently to the prevention of risk factors for conditions of the nervous and cardiovascular system (atherosclerosis).
According to international guidelines, in order for our diet to have positive effects on blood cholesterol levels this must contain 10g/day of LA and 2g/day of ALA, which indeed respects the optimal ratio of 5:1.
As for alpha-linolenic acid (ALA), flax seeds, chia seeds, and walnuts are particularly rich; to a lesser extent it is also present in green leafy vegetables and legumes. As for long-chain omega-3 (EPA and DHA) fatty acids, the best source is cold-sea fish such as mackerel, tuna, and sardines, but salmon is also a good source of omega-3 fats. Linoleic acid (omega-6) is present in seed oils (corn, sunflower, soy, etc.) and in various types of nuts such as almonds, cashews, pistachios, and peanuts. The American Heart Association has stated that the omega-6 fatty acids provided by the consumption of vegetable oils, nuts, and seeds is beneficial when it is part of a healthy and balanced diet where saturated fats have been replaced by polyunsaturated fats.
Knowing the nutrients and foods we eat allows us to understand whether we are following a proper and balanced diet or not. Completely depriving yourself of fats and carbohydrates is never a wise choice as they are essential for our body’s well-being.
We must always keep in mind that it is not the single nutrient that makes the diet but rather it is the wise combination of them and a proper lifestyle (which also includes daily physical activity) that allows us to live a healthy life.
Source:
Regulation (EU) no. 432/2012
Liguri; Nutrizione e dietologia – aspetti clinici dell’alimentazione; Zanichelli
Colli, P. Rossi, F. Marzatico – Viaggio negli alimenti – Calderini (2007)
Tom P. Coultate – La chimica degli alimenti – Zanichelli (2017)
Gli acidi grassi essenziali (EFA) “vitamina F” Omega-3 e -6 – http://didattica.uniroma2.it/assets/uploads/corsi/146788/Lezione_16_07052013.pdf
Simopoulos AP; The importance of the ratio of omega-6/omega-3 essential fatty acids; Biomed Pharmacother. 2002 Oct;56(8):365-79
https://www.healthline.com/nutrition/omega-3-6-9-overview#section3
http://www.nutrition-foundation.it/apb-alimentazione–prevenzione-benessere-n-1—aprile-2014.aspx
Gomez Candela, L.M. Bermejo Lopez, V. Loria Kohen; Importance of a balanced omega6/omega3 ratio for the maintenance of health. Nutritional recommendations; Nutr.Hosp.; 2011; 26(2):323-329