Nutrition Hotline
by Reed Mangels, PhD, RD
This issue’s Nutrition Hotline concerns whether consuming fish benefits the heart and, if so, what that means for vegetarians and vegans.
QUESTION: “I am a vegan and am concerned about heart disease. I have read that fish oil is an important part of a diet to prevent heart disease. Do I need to use fish oil?” AR, via e-mail
ANSWER: Let’s begin to answer your question by looking at some terminology. Fatty fish and fish oil contain 2 unusual kinds of fats, docosahexaenoic acid (DHA for short) and eicosapentaenoic acid (EPA). These fats, along with alpha-linolenic acid, are in a group of fats called omega-3 fats. EPA and DHA are often cited as being the beneficial components of fish oil.
A number of studies have looked at the benefits of eating fish or using fish oil to reduce the risk of heart disease. Recently, researchers combined the results of studies involving more than 200,000 individuals and found that, compared with those who never ate fish or those who ate fish less than once a month, those eating fish once per week had a 15 percent reduced risk of dying from heart disease, while those eating fish 5 or more times per week had almost a 40 percent reduction in risk.1 Each 20 gram-per-day increase in fish intake was related to a 7 percent lower risk of dying from heart disease.1
Results like these have led some medical experts to recommend that people eat fatty fish or use fish oil supplements. In early September 2004, The Food and Drug Administration approved a qualified health claim for foods containing omega-3 fatty acids, mainly fatty fish. The labels on these foods can now say,
“Supportive but not conclusive research shows that consumption of EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease.…”
The FDA approved a similar statement, for dietary supplements containing EPA and DHA omega-3 fatty acids, earlier.
These results showing a benefit of fish oil or fatty fish may not apply to vegetarians, however. Vegetarian diets contain a number of protective factors, and fish oil may not convey any added benefits. Most studies showing positive effects of fish consumption have compared diets high in fish to diets high in meat.
It makes sense that replacing saturated fat- and cholesterol-laden meat with fish would provide health benefits for the general public. Would vegetarians who are already eating healthful diets experience similar benefits if they added fish or fish oil? We don’t really know, but several studies show that vegetarian diets compare favorably with diets that include fish:
- In a large study from the U.K., lacto-ovo vegetarians and fish-eaters had similar blood cholesterol levels. Vegans had the lowest levels of cholesterol, and meat-eaters had the highest levels.2
- Similarly, high blood pressure was most common in meat-eaters; lacto-ovo vegetarians and fish-eaters had intermediate levels of high blood pressure; and vegans had the lowest prevalence of high blood pressure.3
- Mortality from heart disease was 20 percent lower in occasional meat-eaters, 34 percent lower in those who ate fish but not meat, 34 percent lower in lacto-ovo vegetarians, and 26 percent lower in vegans compared to regular meat-eaters.4 The number of vegans was small, though; these results should not be used to suggest that a vegan diet isn’t as good as a diet that includes fish or dairy products.
EPA and DHA are not considered to be essential for humans because we are able to produce them from alpha-linolenic acid, which is an essential fat. The question of how much EPA and DHA we are able to make from alpha-linolenic acid is an area that is being researched and debated. It does appear, however, that some conversion does occur, so it is important for vegans and vegetarians to include sources of alpha-linolenic acid in their diet on a regular basis. These sources include flax seed, flax seed oil, canola oil, soy products, hemp products, and walnuts. Avoiding trans fats (from food like margarine and commercial baked goods containing hydrogenated fats) can help to keep these fats from interfering with EPA and DHA production. Using less sunflower, safflower, corn, and sesame oils and more, canola, and olive oils can also help to encourage DHA and EPA production. Since we are not certain what other factors influence how much EPA and DHA an individual can produce from alpha-linolenic acid, some people opt to use DHA supplements from microalgae as a simple way of insuring adequate intake.
While the type of dietary fat is one factor that can reduce risk of heart disease, there are other important steps vegans and vegetarians can take to promote heart health. These include:
- Exercising regularly
- Avoiding obesity
- Eating a variety of plant foods to supply fiber, antioxidants, and phytochemicals
- Being sure to get adequate vitamin B12, folate, and vitamin B6 to help keep blood homocysteine levels low
- Eating less saturated fat, trans fats, and cholesterol
- He K, Song Y, Daviglus ML, et al. 2004. Accumulated evidence on fish consumption and coronary heart disease mortality: a meta-analysis of cohort studies. Circulation 109:2705-11.
- Appleby PN, Thorogood M, Mann JI, Key TJA. 1999. The Oxford Vegetarian Study: an overview. Am J Clin Nutr 70 (suppl):525S-31S.
- Appleby PN, Davey GK, Key TJ. 2002. Hypertension and blood pressure among meat eaters, fish eaters, vegetarians and vegans in EPIC-Oxford. Public Health Nutr 5:645-54.
- Key TJ, Fraser GE, Thorogood M, et al. 1999. Mortality in vegetarians and nonvegetarians: detailed findings from a collaborative analysis of 5 prospective studies. Am J Clin Nutr 70 (suppl):516S-24S.
