At a glance, omega-3 fatty acids are essential polyunsaturated fats which are numerously beneficial for our health. However, the body can’t make them from scratch so we must get them from food or supplements.
Out of all types, the main and most important omega-3 are: ALA, DHA, and EPA.
ALA (alpha-linolenic acid)
ALA, the most common omega-3 fatty acid in your diets, is mostly found in vegetable oils, nuts (especially walnuts), flaxseeds, leafy vegetables (such as kale or spinach), and some animal fat (especially in grass-fed animals). The human body generally uses ALA for energy. It can also be converted into EPA and DHA during the digestive process but only at a small percentage, which is not sufficient to maintain good health.
EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid)
EPA & DHA are long-chain fatty acids that come mainly from seafood, including fatty fish and algae. Your body uses EPA to produce signaling molecules called eicosanoids which play numerous physiological roles and reduce inflammation while DHA is a key component of all cell membranes and is found in abundance in the brain and retina. Studies have shown that EPA and DHA are important for proper development of neuronal, retinal, and immune functions as well as may affect many aspects of cardiovascular health.
From ALA to EPA & DHA?
ALA is not biologically active until converted into EPA or DHA; if not converted, it is simply stored or used as energy like other fats. On average, only 1–10% of ALA is converted into EPA and 0.5–5% into DHA. The conversion rate also depends on adequate levels of other nutrients, such as copper, calcium, magnesium, zinc, iron, and vitamins B6 and B7. The modern diet, especially vegetarianism, lacks some of these. In addition, some omega-6 fatty acids compete for the same enzymes needed for this process. Therefore, the high amount of omega-6 in the modern diet may reduce the conversion of ALA to EPA and DHA.
Other than the mentioned types, at least eight other omega-3 fatty acids have been discovered such as hexadecatrienoic acid (HTA), stearidonic acid (SDA), or docosapentaenoic acid (DPA), which also occur in some foods but are not considered essential.
The Bottom Line
In a nutshell, the most important omega-3s are EPA and DHA. If you can’t eat fish or don’t like fish, an omega-3 supplement is an equivalent alternative. Algae-based supplements are an option if you are a vegetarian or allergic to seafood.