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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

The role of vitamin C in the body may be even greater than previously believed. New research has found that vitamin C helps convert mouse embryonic stem cells growing in the laboratory into heart muscle cells.1

Embryonic stem cells are unspecialized cells that are derived from the very early stages of fetal development. These cells can convert into any type of cell in the body through a process termed differentiation. Researchers hope that the ability to transform these cells into viable heart cells in the laboratory can lead to effective treatments for heart failure—the inability of the heart to pump enough blood to properly supply the body. Heart failure occurs when the heart is significantly damaged, often from a heart attack or genetic disease.

The American Heart Association estimates that more than 50,000 heart-failure patients die each year in the United States alone. Perhaps the ability to transplant healthy heart cells into the sick hearts of these patients will keep these patients living longer and better lives.

“Although the findings of this study are very preliminary with respect to their impact on human lives, this line of research has enormous implications for the future care of thousands of patients who develop heart failure each year,” said Robert O. Bonow, M.D., president of the American Heart Association in an official statement. “Identifying mechanisms to transform stem cells into differentiated heart muscle cells is an important step toward clinical reality.”2

For their study, which was published in the April 15, 2003 issue of Circulation: Journal of the American Heart Association, researchers tested 880 bioactive substances, including drugs and vitamins, to see if they prompted mouse stem cells to transform into heart cells.3

“We only got one out of the 880 to light up, and that was from ascorbic acid, the chemical commonly known as vitamin C,” said Richard T. Lee, M.D., senior author of the study. Lee is an associate professor of medicine at Harvard Medical School and Brigham and Women’s Hospital in Boston and a lecturer in biological engineering at the Massachusetts Institute of Technology in Cambridge, Massachusetts.

Many benefits of vitamin C have been attributed to its ability to neutralize oxidants. However, the researchers of this study believe that the ability of vitamin C to promote cardiac differentiation of stem cells is unrelated to its antioxidant abilities. This is because other antioxidant compounds tested, including vitamin E, did not promote the development of heart cells.

“The real significance of the study is that it indicates that we will be able to find other ways to generate heart cells from stem cells more efficiently,” said Lee. “It also raises interesting questions about the role of vitamin C in the development of the embryo’s heart.”

—Dr. Marc Ellman