GRONINGEN, THE NETHERLANDS. Alpha-linolenic acid (ALA) and docosahexaenoic acid (DHA) have both been shown to reduce the risk of heart disease. Studies using isotopically labeled ALA have shown that it can be converted by the body to EPA (eicosapentaenoic acid) and DHA, but how significant this conversion is in actual practice is not known.
Fish oil is rich in DHA, whereas flaxseed oil is rich in alpha-linolenic acid (ALA) and borage oil contains gamma-linolenic acid (GLA). Because vegans do not consume any type of meat, including fish, they tend to have low intakes of long chain polyunsaturated fatty acids (LCP). How much ALA is converted to DHA and EPA? Does APA supplementation significantly increase DHA levels?
Dutch researchers now report that the conversion of alpha-linolenic acid (ALA) to DHA in vegans (strict vegetarians) is negligible and that supplementation with alpha-linolenic acid does not increase DHA levels significantly. Their trial included 6 healthy men and 3 healthy women between the ages of 20 and 60 years who were adhering to a vegan diet (no meat, fish, eggs or dairy products). The participants were randomized to receive either 2.01 grams of alpha-linolenic acid (4 ml linseed oil; also known as flaxseed oil) daily or 1.17 grams of GLA (6 ml borage oil) daily for a four-week period. This was followed by a four-week period during which all the participants received both supplements. Blood samples were taken and analyzed for fatty acid content at the start of the trial and after four and eight weeks. Neither the flaxseed oil nor the borage oil by themselves increased blood levels of EPA or DHA, but their combination did produce a statistically significant, but nevertheless negligible, increase in EPA and DHA in the cholesterol and triglyceride fractions of the blood. The researchers pointed out that a clinical trial involving omnivores (meat and fish eaters) gave similar results and concluded that ALA supplementation is not effective in increasing DHA levels significantly.
Fokkema, M.R., et al. Short-term supplementation of low-dose gamma-linolenic acid (GLA), alpha-linolenic acid (ALA), or GLA plus ALA does not augment LCP omega-3 status of Dutch vegans to an appreciable extent. Prostaglandins, Leukotrienes and Essential Fatty Acids, Vol. 63, November 2000, pp. 287-92