The food industry has been urging me to eat fish. The supplement companies have been urging me to take fish oil supplements. They claim that omega-3 fatty acids prevent heart attacks. Some people even claim that a baby cannot develop a normal brain unless its mother ate fish or took fish oil supplements. In contrast, nutrition scientists tell me that green plants are an excellent source of the only omega-3 fatty acid that is essential in human nutrition. This could explain why populations that rarely if ever eat fish can have healthy hearts and healthy brains. In fact, the healthiest populations are the ones that eat very little fat of any kind and lots of vegetables.
All of the omega-3 fatty acids in the food supply came originally from the green plants and blue-green algae (cyanobacteria) that are at the bottom of the food chain. An omega-3 fatty acid called alpha-linolenic acid is an important part of the thylakoid membranes that are involved in photosynthesis. No animal can make an omega-3 fatty acid. Animals do not have the enzymes that would be needed to put a double-bond in the omega-3 position in the hydrocarbon chain of a fatty acid. However, animals can lengthen the carbon chain of an omega-3 fatty acid. Thus, fish and other animals (including human beings) can convert alpha-linolenic acid to longer-chain omega-3 fatty acids, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). For this reason, you can find EPA and DHA in fish but not in ordinary plant-source foods.
According to the Food and Nutrition Board of the National Academy of Sciences, there is only one omega-3 fatty acid that is essential in human nutrition. It is the alpha-linolenic acid that is found in thylakoid membranes of the chloroplasts of green plants. For this reason, you can get this omega-3 fatty acid from eating green vegetables. Flaxseeds, hempseed, and walnuts are also good sources of alpha-linolenic acid.
You need only a little bit of alpha-linolenic acid from your food. The dietary requirement for the two essential fatty acids (alpha-linolenic acid and an omega 6 fatty acid called linoleic acid) was discovered only after hospitalized patients started being fed fat-free solutions for an extended period. Yet even their need for these essential fatty acids could be met by rubbing a little bit of vegetable oil on the skin.
For years, many people have been urging the public to eat fish or take fish oil supplements, to reduce the risk of heart attack. Populations that eat a lot of omega-3 acids, from cold-water fish, do have a somewhat lower-than-expected rate of fatal heart attacks. However, this is probably because of the blood-thinning effects of omega-3 fatty acids, which could also lead to more deaths from major bleeding. If you really want to make yourself heart-attack-proof, eat a low-fat, plant-based diet to keep your total cholesterol below 150 mg/dL.
Some manufacturers of baby formula have been adding DHA so that the formula will have a DHA content similar to that of breast milk. Yet whether the additional DHA provides real benefits to the baby is still unclear. However, these studies do raise concerns about giving too much long-chain omega-3 fatty acid without also providing a supplement of arachidonic acid.
I do not know whether any vegans (such as pregnant women or the elderly) would benefit from supplementation with the longer-chain omega-3 fatty acids. If these supplements are beneficial, it would be best for them to come from a plant source. Plants are less likely to be contaminated by the pollutants that build up in animal tissue.
Photo by albertstraub