Monday, February 25, 2008

Nutrition: Diet and Heart Disease

Robert M. Russell, M.D., and Alice H. Lichtenstein, D. Sc.Alice H. Lichtenstein, D. Sc., is an Associate Professor of Nutrition in the School of Nutrition Science and an Associate Professor of Family Medicine, Community Health at Tufts University School of Medicine. Her research investigates the behavior of lipoprotein molecules. particles, predictive factors for changes in blood lipids induced by diet in individuals. Dr. Lichtenstein is on the Editorial Board of the Journal of Nutrition and Atherosclerosis.

Being Thin Is Not Necessarily the Solution
RMR
How important a factor is dietary fat intake in the development of coronary artery disease? Put another way, if a person has a high fat diet but stays relatively thin will their arteries be okay?AHLYou can't tell by looking at someone whether they are of a desirable body weight or overweight, or their risk of developing heart disease. Each person is different.First, you have to know how much fat (lipid) is in your blood (see Table 1 below for more detail). Most physicians do this blood test every time you have a check-up or annual medical exam. The most important factor affecting blood cholesterol levels is how much saturated fat and cholesterol you eat.

Risk Factors Vary with the Individual, but They Do Add Up
RMR
What risk factors affect your blood lipid levels? Alice, you mentioned the various risk factors for coronary artery disease and I wonder if you would list them in order of importance as a review and, secondly, could you review the main sources of saturated fats in our diet and the mechanism whereby saturated fats give rise to elevated cholesterol levels?

AHL
The significant risk factors are hypertension, family history of cardiovascular disease, current cigarette smoker, hypertension, low HDL cholesterol (the good cholesterol) and diabetes. Although not considered independent risk factors, obesity and physical inactivity should also be taken into consideration. No one risk factor is more important than another (see Table 2 below).

Major Sources of Saturated Fat in the Diet
AHL
The American Heart Association (AHA) and the National Cholesterol Education Program (NCEP) have issued recommended guidelines, Step 1 and Step 2 they're called, for the dietary treatment of too much cholesterol Table 3. The patient should be first counseled to follow a Step 1 diet. If a patient is already on a Step 1 diet, or an acceptable response is not achieved, the patient should be advised to follow a Step 2 diet by further decreasing their saturated fat intake to 7% of calories and their cholesterol intake to 200 mg/day. For this strategy to be effective, you'll probably require the help of a registered dietitian. Usually, decreasing the total fat content of the diet is easier to do than decreasing the saturated fat content. In order to decrease effectively the saturated fat content, it is important to know its major sources. These include animal fats such as meat and full fat dairy products and, depending on one's tastes, a few selected plant oils (Table 7). The plant oils, frequently termed tropical oils, include coconut oil, palm oil, palm kernel oil and cocoa butter and contain a fair amount of saturated fat. However, they do not tend to be used in high levels in the United States.For Americans with high blood lipid levels, the focus should be on decreasing full fat dairy products and meat. Many non-fat, reduced-fat and low-fat dairy products are now available. To reduce the intake of saturated fat from meat, buy cuts of meat with the least amount of visible fat; trim meat of excess fat; with poultry, remove the skin before eating; and, of course, cut down on the size portion of meat actually consumed.

The other potential source of animal fat can come from cooking, as discretionary fat is added during food preparation. We recommend that individuals switch from animal fats such as lard or butter to vegetable oils.The other dietary factor which elevates blood cholesterol levels is dietary cholesterol.

Major sources of dietary cholesterol are eggs and animal fats (both dairy and meat). By decreasing the consumption of animal fat, in addition to saturated fat, dietary cholesterol intake should also decrease.

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