Flaxseed oil is being heavily promoted as an alternative to fish oil. The health benefits of fish oil are believed to derive principally from two omega-3 fats, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). EPA and DHA. The body uses EPA to create many hormone-like substances that reduce inflammation and other “excited” states in the body, such as raised blood pressure. Also, eight percent of the brain is composed of EPA and DHA, and one wants to be sure this 8% stays healthy!
Flaxseed oil contains a third, plant-based omega-3, alpha-linolenic acid (ALA). Other foods, especially walnuts and hemp, contain ALA, but at about 7 grams per tablespoon, flaxseed oil is by far the richest source.
The main problem with ALA is that to have the good effects attributed to omega-3s from fish, it must be converted into EPA and DHA. The body uses various enzymes to convert ALA to other omega-3s, and the process is not very efficient, especially as one gets older. Estimates of the rate of conversion range from 5% to 25%. In order to make sufficient amounts of EPA and DHA, one needs to consume 5 or 6 times more ALA than if one relies on fish oil alone. Also, women convert ALA to the other omega-3s more efficiently than men, largely so they can meet the nutritional demands of their infants during pregnancy and breastfeeding. As a result, only a small fraction of flax has omega-3’s effects.