Nutrition Hotline
By Reed Mangels, PhD, RD
QUESTION: Has Vegetarian Journal addressed the DHA issue? I've read several things which make it sound important for vegetarians.
N.B., CA
ANSWER: DHA stands for docosahexaenoic acid. DHA is a polyunsaturated fatty acid. High levels of DHA are found in our brains and in our retinas, and it appears to be important for both brain function and for vision. DHA is especially important in infants to insure appropriate brain and retinal development.
Vegetarian diets are generally low in DHA, since major food sources are fish, animal brains, cow's liver, and eggs (especially eggs from hens fed flaxseed).
Vegans generally consume no DHA. The good news is that we do not have to get DHA from food. Our bodies are able to produce DHA from another fatty acid called alpha linolenic acid. However, we are not very good at doing this, and when we eat large amounts of another fatty acid called linoleic acid or trans fatty acids, our bodies make even less DHA. Studies have shown that vegans and other vegetarians have lower levels of DHA in their blood than do non-vegetarians. We do not know, however, whether people who eat little or no DHA are more efficient at using it for mental and visual function. There is no evidence that vegetarians exhibit any symptoms of DHA deficiency.
DHA is important in the developing fetus and in early infancy. During pregnancy, DHA appears to be transferred to the fetus through the placenta, even in vegetarians whose DHA intakes are low. Although the level of DHA in human milk from vegans was lower than that of non-vegetarians in one study, it was still higher than that found in cow's milk formula, which does not contain DHA. Additional research is needed on DHA needs of vegetarian and vegan infants, especially premature infants. Premature infants are born with lower levels of DHA. Until more research can be conducted on the DHA status of vegetarians, vegetarians can do several things to improve their DHA status. One positive step is to include some foods rich in alpha-linolenic acid, which will provide material for your body to make DHA. These foods include flax seed, flaxseed oil, walnuts, soy products (not fat-reduced), and canola oil. Another step is to limit foods rich in linoleic acid like corn, sesame, and safflower oils. Also, you can try to avoid trans fatty acids which come from partially hydrogenated fats and are found in many commercial crackers, cookies, and margarines. Pregnant and breast feeding women may need to be especially conscious of these recommendations in order to positively influence the DHA status of their infants. Increased maternal DHA has been shown to increase blood DHA levels in infants. There are DHA supplements on the market, some of which are derived from algae. These have been shown to raise blood levels of DHA in vegetarians but have not been shown to have other beneficial effects. These may be an option for some vegetarians. Some supplements are in the form of gelatin-based capsules with the gelatin possibly derived from animal bones, so if you decide to use DHA supplements, check on what the capsules are made from. Additionally, there is some evidence that significant amounts of DHA will affect immune function. Use of vitamin E supplements along with the DHA supplements may reduce or eliminate the effects of DHA on the immune system.
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