The precursor of the group of omega-3 fatty acids is alpha-linolenic acid (ALA). It is regarded as essential because it is necessary for the development and proper functioning of the body, which cannot synthesise it by itself. Itand must therefore be provided by food. From this compound the body synthesises other omega-3 fatty acids, especially eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. However, the rate of conversion of ALA to DHA is too low to cover the body’s needs in DHA, and therefore DHA is also regarded as essential and must be supplied in the diet.
What are their effects on health?
Omega-3 fatty acids are necessary for the development and functioning of the retina, brain and nervous system. Adequate intake of omega-3 is therefore essential for women of childbearing age, pregnant and breastfeeding women, and children.
Regarding cardiovascular health, scientific data also show that consumption of omega-3 fatty acids promotes:
- a decrease in blood pressure in people with hypertension;
- a decrease in the amount of triglycerides in the blood, a type of fat which, in excess, can contribute to the development of heart disease;
- in people with a history of cardiovascular disease, a reduction in cardiovascular morbidity and mortality.
However, ANSES reiterates that prevention of cardiovascular diseases is mainly based on health and dietary measures, combining a diverse and balanced diet with regular physical activity.
In addition, recent data show that EPA and DHA play a role in brain function in adults and during ageing, suggesting a positive effect on maintaining mental health (depression, dementia including Alzheimer's disease), although further studies are required to confirm and clarify the effects of these fatty acids.
Lastly, EPA and DHA are also involved in the prevention of age-related macular degeneration (AMD). Indeed, a deficiency in these fatty acids may increase the risk of AMD.
Where are omega-3 fatty acids found?
The foods richest in omega-3 are derived from terrestrial plants (walnuts, rapeseed oil, soybean oil, linseed oil, etc.) containing ALA, and marine animals (oily fish such as salmon, tuna, mackerel, herrings, sardines, anchovies, etc.) that contain EPA and DHA.
See the CIQUAL Table for:
At the domestic level, some oils rich in omega-3 fatty acids (mainly ALA) cannot tolerate frying and very high cooking temperatures and should therefore be used for seasoning.
However, in France, it is terrestrial animal products (meat, eggs, dairy products, etc.) that contribute most to intake, because even though they contain lower levels of omega-3 fatty acids, they are consumed in greater quantities than vegetable oils or oily fish.
The Agency's work
In 2010, the Agency defined population reference intakes for ALA, EPA and DHA in adults, pregnant women, breastfeeding mothers, infants, children and adolescents. The linoleic acid/alpha-linolenic acid ratio is often mentioned, but is not very relevant as long as physiological needs in linoleic acid and ALA are met. Nevertheless, this ratio is important in the event of an imbalance from a deficiency in ALA intake and/or from excessive linoleic acid intake, and more so if it is accompanied by a simultaneous deficiency in EPA and DHA intake.