At one time, the only dietary advice patients received from their doctors on how to lower their risk for heart disease was to cut back on fat and cholesterol. Today, however, decades of research have indicated that far more than just fat and cholesterol may influence the development of heart disease, including different types of fat, fiber, whole grains, and antioxidant nutrients.
Because the body of research has become larger and results are sometimes conflicting, researchers reviewed 147 published studies to determine what the most compelling evidence showed regarding diet and heart disease. Their findings are published in November 27, 2002 issue of the
Journal of the American Medical Association
About the study
Researchers from the Harvard School of Public Health searched an online database of published medical studies (MEDLINE) to identify studies of diet and heart disease published through May 2002. They identified 147 studies, including both clinical trials and epidemiologic (observational) studies.
The studies they reviewed investigated various dietary components, including cholesterol, total dietary fat, omega-3 polyunsaturated fatty acids,
fatty acids, monounsaturated fatty acids, carbohydrates, glycemic index, fiber, folate, and specific dietary patterns (such as substituting unsaturated fat for saturated fat).
The researchers evaluated each study for relevance and quality—paying particular attention to conflicting or consistent results—to determine which dietary strategies for the prevention of coronary heart disease had the strongest evidence. They gave more weight to larger studies and those with measurable endpoints.
On the whole, the data revealed three dietary strategies that appeared most effective in preventing heart disease:
Substituting nonhydrogenated unsaturated fat (found in olive, canola, and soybean oils, as well as fatty fish, avocado, and nuts) for saturated fat (found in butter, whole milk, and red meat) and
fat (found in margarine and processed foods).
Increasing consumption of omega-3 fatty acids from fish, fish oil supplements, or plant sources, such as flaxseed, leafy greens, walnuts, tofu, and canola and soybean oil.
Consuming an overall diet rich in fruits, vegetables, nuts, and whole grains and low in refined grain products, such as white bread, white rice, potato chips, pastries, and cookies.
Other factors played a role, but, according to the authors, the results are inconclusive and remain “unsettled” on issues such as the optimal amount of monounsaturated and polyunsaturated fat in the diet, the optimal balance between omega-6 and omega-3 fatty acids, the optimal amount and sources of protein in the diet, and the effects of different plant nutrients (phytonutrients), vitamins, and minerals. For example, early data showed promise for vitamin E supplements in the prevention of heart disease, but the results of more recent trials were disappointing (research in this area continues).
The review is limited in that its conclusions are only as good as the results of the studies it analyzed. That is, each of the 147 studies had limitations that affected the validity of their results. And the authors acknowledge that the types of studies that best control for “confounding factors” (factors other than diet that can influence heart disease risk) are “surprisingly few” in the literature they reviewed.
How does this affect you?
Because research is ongoing, it is unknown what the “perfect” diet for preventing heart disease is (if such a diet even exists). But the results of this study present compelling evidence for certain dietary strategies that may most benefit heart health.
If you are currently following a diet prescribed by your doctor for preventing or controlling heart disease, don’t change your regimen without first consulting your doctor. If you need assistance in making dietary changes, ask your doctor for a referral to a registered dietitian willing to prescribe an individualized eating plan that takes this new research into account.
Heart disease is the leading cause of death in many Western countries (including America) and worldwide rates of the disease are rising. The good news, however, is that heart disease risk can be positively influenced by controllable lifestyle factors. As the authors of this study point out, eating a healthful diet, in addition to getting regular exercise, not smoking, maintaining a healthy weight, and managing stress, may prevent the “majority” of cases of cardiovascular disease in Western societies.
Please be aware that this information is provided to supplement the care
provided by your physician. It is neither intended nor implied to be a
substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER
IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the
advice of your physician or other qualified health provider prior to
starting any new treatment or with any questions you may have regarding a