For the past two weeks I have discussed heart disease.

There was some evidence to suggest that the atherosclerotic process (the buildup of plaque in the arteries of the heart) is similar in all people, and that cholesterol levels tended to predict the coronary risk. There were also studies that showed that the disease process could be slowed and in some cases reversed by lowering blood cholesterol levels either by diet or by drugs.So, the question could be asked, "What do I do if I am worried about heart disease?"

The first step, according to the National Cholesterol Education Program, is to see if you have too much cholesterol in your blood. This can be done by having your doctor or a lab that he recommends take a blood sample from your finger or your arm. If the level is more than 200 milligrams per deciliter of blood (mg/dl) you should have a second test to confirm the reading. A blood cholesterol level of 240 mg/dl or greater is considered "high," but any level above 200 mg/dl increases your risk for heart disease.

More and more, physicians are looking at sub-fractions of cholesterol such as HDL (the good cholesterol fraction) and the "bad" cholesterol, LDL. As an example of the role these fractions play, there is some evidence that abnormally high HDL levels - below 40 mg/dl - may signal trouble even if cholesterol or LDL are normal. On the other hand, high levels of total cholesterol are not nearly so frightening if you have a high HDL level. Coronary risk is also affected by several lesser-known cholesterol carriers, such as lipoprotein This carrier is thought to be inherited, and low levels may predispose some people to heart disease even if total cholesterol levels are normal.

If your total cholesterol is high, or if your doctor thinks you are at risk because of one of the other cholesterol readings, he will have you work on the following areas:

- Diet. Among the factors you can do something about, diet has the largest effect on blood cholesterol. Saturated fat raises your blood cholesterol level more than anything else you eat. Dietary cholesterol also increases blood cholesterol, but even if you didn't eat any cholesterol, your body would manufacture enough for its needs. So, eat less high-fat food (especially food from animal sources), replace part of the saturated with unsaturated fat, and eat more foods high in complex carbohydrates (starch and fiber).

- Physical activity. Although it is not clear whether physical activity can prevent atherosclerosis, regular exercise may help you control weight, lower blood pressure and increase your good cholesterol, HDL.

- Address other risk factors. If you smoke cigarettes, or if you have high blood pressure, the risk associated with high cholesterol increases dramatically. For instance, if you have high blood pressure along with high cholesterol, the risk increases by a factor of six; if you smoke (with high cholesterol), the risk is increased more than 20 times.