After my recent column on margarine and butter, a number of women asked me about cholesterol and fat. The scientific information on cholesterol and fat is confusing, so I asked my colleague, Dr. Benjamin Caballero, director of the division of nutrition at the Johns Hopkins School of Public Heath, to explain what we should be doing about cholesterol and fat in our diets to improve our health.
Why is there concern about cholesterol levels?
Studies have repeatedly shown that people with high blood cholesterol levels are at increased risk for coronary heart disease. The three most important risk factors for coronary heart disease are smoking, high blood pressure and high blood cholesterol.
Since heart disease is the leading cause of death for women in the United States, this is of great importance to us.
Q: How do you get high blood cholesterol?
The kind of genes you inherit and the fats and cholesterol you eat in your diet are directly related to the level of cholesterol in your blood.
What should your cholesterol level be?
Many doctors now screen patients routinely for cholesterol levels. The "desirable" level is below 200 milligrams of cholesterol per deciliter of blood. Levels between 200 and 240 are considered borderline, and levels above 240 are related to a risk of heart disease and may require steps to reduce the level.
Over half of the population of the United States has blood cholesterol levels above 200 and 25 percent have levels above 240. If your cholesterol is above 200, your physician also may get an additional test, called a "lipoprotein profile," to assess your risk.
What does the lipoprotein profile tell us?
A: Most cholesterol travels in the blood attached to proteins called lipoproteins. Low-density lipoproteins (LDL) carry cholesterol from the liver to everywhere in the body. By spreading cholesterol all around the body, LDL contributes to too much cholesterol in the arteries. We call LDL the "bad" cholesterol.
On the other hand, high-density lipoproteins (HDL) are the "good" cholesterol. They pick up cholesterol from all over the body and carry it to the liver so it can be disposed of. The actual risk of coronary heart disease is determined by how much HDL is available to remove circulating cholesterol, balanced by the amount of LDL that is spreading cholesterol around. Desirable levels of these lipoproteins is less than 130 milligrams per deciliter of blood for LDL and more than 35 milligrams per deciliter for HDL.
Women and men differ in how the ratio between these good and bad lipoproteins changes over the life span. For men, LDL/HDL ratios change during puberty and remain constant thereafter, while in women they change after menopause. This
difference may account for the dramatically increased risk of heart disease for women over 65.
Q: What about fat and cholesterol in the diet?
Everyone should eat less fat, but some fats are more harmful than others. Whether the fat you eat is good or bad for you has a lot to do with whether it contributes to "good" cholesterol (HDL) or "bad" cholesterol (LDL).
* Saturated fats (mostly animal fats) increase bad cholesterol levels (LDL).
* Polyunsaturated oils (corn, soybean, safflower) lower overall blood cholesterol but unfortunately lower LDL and HDL levels, thus lowering the good with the bad.
* Olive oil, a monounsaturated fat, is the best fat to use. It helps maintain a better ratio of good to bad cholesterol. This may be one reason why Mediterranean people, who consume mostly olive oil, have much lower heart disease than do Americans.
Q:Q: How can we put this information to practical use?
* Eat less fat. The typical American diet has too much fat. Fat should contribute no more than 30 percent of your total daily calories.
* Eat less saturated fat. There is no question that it increases blood cholesterol levels and LDL (the bad cholesterol). Dairy products are a major source of saturated fat, as are coconut oil, cocoa butter and palm oil.
* Replace saturated fat with olive or canola (rapeseed) oil.
* Reduce your cholesterol intake. And remember that cholesterol is not a fat, so foods labeled low in cholesterol may be high in fat content, and foods labeled low in fat may be high in cholesterol. Remember to read before you eat.
For more information, write to the National Cholesterol Education Project at the National Heart, Lung and Blood Institute, C-200, lTC Bethesda, Md. 20892.
Dr. Matanoski is a physician and professor of epidemiology at the Johns Hopkins School of Hygiene and Public Health.