The heart-healthy benefits of fish oil are well known. Many research studies have demonstrated a relationship between fish consumption and a reduced risk of developing heart disease. However, little data exists on the benefit of fish consumption for diabetics. Until now, that is.
Researchers at Harvard examined the dietary records of more than 5,000 female nurses diagnosed with type 2 diabetes who were followed for 16 years as part of the ongoing Nurses’ Health Study. They found that the more fish the nurses ate, and consequently the more omega-3 fatty acids they consumed, the lower their risk was of developing or dying from heart disease.
The largest reduction in risk was seen in women who ate the most fish – at least five times per week – as they were 64% less likely to develop heart disease than women who seldom ate fish. These same women were also 52% less likely to die of heart disease. These results were published in the April 15, 2003 issue of Circulation: Journal of the American Heart Association.1
“High consumption of fish – two to four servings per week – can substantially reduce the risk of coronary heart disease and mortality among people with type 2 diabetes,” says Frank B. Hu, M.D., lead author of the study and associate professor of nutrition and epidemiology at the Harvard School of Public Health.
Although this study only involved women, Dr. Hu told Life Extension magazine that he believes “the results can apply to diabetic men as well.”
Researchers credit most of the cardiovascular protection obtained from fish consumption on their high omega-3 fatty acid composition. Although the exact mechanisms are still unclear, these substances have shown numerous cardiovascular benefits, including helping to prevent the development of blood clots, averting a potentially fatal irregular heart rhythm and reducing blood pressure. Omega-3 fatty acids have also been proven to lower triglyceride levels in the bloodstream.
There are primarily two types of omega-3 polyunsaturated fatty acids. The first type, alpha-linolenic acid, comes largely from plant oils. The second type, found predominately in fish oils, includes eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). EPA and DHA are labeled “essential” fatty acids because they are necessary for normal development of the brain and retina (the light-sensitive tissue in the back of the eye). The human body can convert a portion of alpha-linoleic acid into EPA and DHA.2
One of the concerns about obtaining EPA and DHA from eating fish is that some species of fish may contain significant levels of environmental contaminants, such as methylmercury, dioxins and polychlorinated biphenyls (PCBs). This might be especially important for children and pregnant or lactating women.3
“This is an unresolved issue,” says Dr. Hu. “Some fish contains more mercury than others. The best way to avoid problems is to vary the type of fish you eat.”
Since the health benefits of fish are apparently derived from their high levels EPA and DHA omega-3 fatty acids, it is assumed that fish oil supplements provide the same cardiovascular advantages. However, fish oil supplements eliminate the risk of consuming environmental toxins. “Our study did not focus on supplements,” says Dr. Hu. “However, theoretically they can be beneficial for type 2 diabetics.”
While omega-3 fatty acids have proven cardiovascular benefits, their use as a therapy for cardiovascular disease should only be in addition to standard medications for the treatments of heart disease under the supervision of a physician.
This issue was addressed in an accompanying editorial written by Scott M. Grundy, M.D., Ph.D., of the Center for Human Nutrition at the University of Texas Southwestern Medical Center at Dallas. Dr. Grundy stated that in future research “supplemental fish oil would have to be add-on therapy to other standard treatment, e.g., antiplatelet drugs, beta-blockers, cholesterol-lowering drugs and angiotensin-converting enzyme inhibitors.”2
—Dr. Marc Ellman