Their biosynthesis takes place via α-linolenic acid, an essential omega-3 fatty acid. Studies come to different results regarding the conversion rate of α-linolenic acid in DHA and EPA.
A study concludes that α-linolenic acid-rich vegetable oil, together with a low linoleic acid diet, increases the EPA level in tissue similar to supplementation with fish oil.
Since the intake of omega-3 fatty acids such as eicosapentaenoic acid and docosahexaenoic acid in Europe is significantly below the recommendations, docosahexaenoic acid and DHA have been offered in the form of capsules and enriched foods for several years. During the treatment of fish oil, this is transesterified from the natural triglyceride form into the ethyl ester form of EPA and DHA using ethanol.
Some studies suggest that the bioavailability of docosahexaenoic acid in the TG form and, in the meantime, some manufacturers of infant formula also add fish oil to their products to meet the needs of infants for omega-3 fatty acids naturally present in breast milk.