Cardiovascular disease and cancer remain the two leading causes of death worldwide. Eating a healthy diet can delay the onset of such diseases and improve longevity. In this context, vegetable oils rich in polyunsaturated fatty acids, in particular omega-3 fatty acids, are particularly recommended. A meta-analysis published last month in the British Medical Journal confirms the beneficial role of omega-3 on health.
Omega-3 fatty acids are a family of essential fatty acids — fatty acids that are essential for the proper development and proper functioning of the body, but that our body does not know how to manufacture. They can nevertheless be synthesized from their precursor, alpha-linolenic acid (ALA) if this is provided by food; it is readily available in soybeans, tree nuts, canola oil, flaxseeds and other plant food sources.
The study published last month aimed to examine the associations between dietary intake and tissue biomarkers of ALA and the risk of all-cause mortality, cardiovascular disease and cancer. A total of 41 articles from prospective cohort studies were included in this meta-analysis, totaling nearly 1.2 million participants. The results showed that dietary ALA intake is associated with a reduced risk of all-cause mortality, cardiovascular disease, and coronary heart disease. And these are not the only virtues of omega-3s.
From ALA, the body synthesizes other omega-3 fatty acids, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). However, the conversion rate of ALA to DHA is too low to cover our daily needs for this fatty acid, so the latter is also considered essential and must also be provided by food. The foods richest in omega-3s come from terrestrial plants that contain ALA (walnuts, rapeseed oil, soybeans, flaxseed, etc.) and marine animals (fatty fish such as salmon, tuna, mackerel, herring, sardines and anchovies, etc.), which contain EPA and DHA.
Omega-3 fatty acids are necessary for the development and function of the retina, brain and nervous system; they are involved in the coagulation process, in immunity, metabolism, etc. Adequate intakes of omega-3s are therefore particularly important for women of childbearing age, pregnant women, breastfeeding women, as well as children and adolescents. A report by the Center for Research and Nutritional Information (CERIN) recommends that adults consume 250 mg of DHA and 500 mg/day of EPA and DHA combined every day.
Although omega-3s have many benefits, it appears that most people consume too little of them on a daily basis. It is estimated that nearly nine out of ten French people have a deficiency in EPA and DHA fatty acids. In this case, omega-3 supplementation is strongly recommended. A recent study involving nearly 26,000 adults showed that omega-3 supplementation, implemented for five years, led to a significant reduction (-18%) in the risk of autoimmune disease.
Their protective effect on the retina, in particular against the onset of age-related macular degeneration (AMD) — a chronic disease that causes progressive loss of vision and the main cause of low vision in people over 50 — has recently been highlighted in a study conducted by French researchers. Omega-3s support vision at the photoreceptor level, but also have anti-inflammatory functions, and limit cell death and vascular development in the retina — three primary mechanisms for preventing AMD, the researchers explain.
Several studies have also highlighted the role of omega-3s in the prevention of cardiovascular disease. Regular consumption of these fatty acids causes a decrease in blood pressure in people with hypertension and also leads to a reduction in the blood level of triglycerides.
In addition, an analysis of 4 cohort studies involving more than 190,000 people from 58 countries, found that consuming at least 175 g of fish (or 2 servings) per week reduced the risk of developing cardiovascular disease by 16% and 18% mortality in people at high risk (or with vascular disease). The effect was greatest with oily fish, particularly rich in omega-3s.
A conclusion shared by a study published in the journal Neurology , which points out that heavy fish eaters are less likely to develop brain disorders and strokes. An MRI scan showed that the brain vessels of regular fish eaters (2-4 times a week) were much healthier than those of people who ate little.
Finally, omega-3s could also play a major role in brain function and as such, could have a positive effect on maintaining mental health during aging. A study in aged rats showed that four weeks of a diet of ultra-processed foods elicited a strong inflammatory response in the animals' brains, along with behavioral signs of memory loss. In contrast, supplementing this diet with DHA prevented memory problems and reduced inflammation almost entirely. Other studies must nevertheless confirm these effects on humans.
