Vegan for Life - Jack Norris [25]
OMEGA-3 FATS IN PLANTS
While plant foods don’t have DHA and EPA, a few provide alpha-linolenic acid (ALA). This is a short-chain omega-3 fat that is essential in diets and technically can be converted to EPA and DHA. It’s found in flaxseeds, hempseeds, chia seeds, canola oil, walnuts, soy oil, and some soyfoods.
A second fatty acid called linoleic acid (LA) is also essential in the diet. This is an omega-6 fat and it’s abundant in commonly consumed oils like safflower and sunflower oil as well as whole plant foods. Americans, including vegans, get plenty of this essential fat.
The problem is that high intakes of the omega-6 fatty acid LA suppress conversion of ALA to DHA and EPA. Experts suggest that for optimal production of DHA and EPA, diets should contain no more than a 4 to 1 ratio of LA to ALA. But the ratio in vegan diets is more typically around 15 to 1.9 That is, vegans are consuming too much of the omega-6 fatty acid LA and sometimes not getting enough of the omega-3 fat ALA. As a result, dietary strategies to boost ALA intake and lower LA intake have become popular among some vegans. But do they work?
Unfortunately, there are no long-term studies looking at blood levels of EPA and DHA in vegetarians when these strategies are used. And short-term studies indicate that it takes large amounts of ALA to increase the amount of DHA in the blood. In fact, for the most part, studies using supplements or food sources of ALA have been largely unsuccessful in raising levels of DHA and only moderately successful in raising levels of EPA.
In addition, it’s not clear that high doses of the short-chain omega-3s are completely benign. In the Nurses’ Health Study, higher intakes of ALA were linked to eye problems, including increased risk of macular degeneration.10 In contrast, the highest intakes of DHA tended to be protective of eye health. These studies were done on only one population by one group of researchers, and the biggest contributors of ALA in omnivore diets are dairy and other animal products, not plant foods. So it’s not clear whether these findings are relevant to vegans. The findings suggest caution regarding high intakes of ALA, but more information is needed before we should draw conclusions.
Based on the little we know, it’s not clear that large amounts of ALA are safe. Nor is it clear that increasing ALA intake boosts blood levels of DHA and EPA. But there is another option for vegans: algae-derived DHA and EPA supplements.
DHA SUPPLEMENTS
Fish get their DHA from algae, and vegans can go to the same source. Preliminary research suggests that a supplement providing 200 milligrams of DHA per day for three months can raise blood DHA levels in vegans by as much as 50 percent.11 Other studies of vegetarians (not necessarily vegans) have also shown the positive effects of taking DHA supplements.12
But because the research on the overall benefits of omega-3s is so conflicting, it’s hard to know whether these supplements are useful for vegans. We are not convinced that they are. On the other hand, we are not convinced that the lower blood levels of DHA and EPA in vegans is unimportant. Until we know more, we are inclined to recommend supplementing with very small amounts, around 200 to 300 milligrams of DHA (or DHA and EPA combined), every two or three days.
Many vegan supplements provide only DHA, but new ones providing both DHA and EPA are becoming available. A few vegan foods such as soymilk, energy bars, and olive oil are also fortified with algae-derived DHA.
MEETING ESSENTIAL FATTY ACID NEEDS
While large intakes may not be advisable, everyone needs to