Keep your HDL high for good health
By the faculty of Harvard Medical School for The Harvard Medical School Adviser

Q: My HDL cholesterol level is just 35, which I know is on the low side. Are there ways to raise HDL without drugs?

A: HDL, which stands for high-density lipoprotein, is often called "good" cholesterol because it protects the heart and circulation. HDL removes harmful LDL ("bad") cholesterol deposits from the walls of vulnerable arteries, then delivers the LDL to the liver for disposal from the body. These beneficial particles also help fight harmful inflammation and blood clots in your arteries.

The higher your HDL cholesterol, the lower your risk of heart attack and stroke. A level of 40 milligrams per deciliter (mg/dL) is desirable. But levels above 60 mg/dL are optimal. Unfortunately, about one-third of Americans have low HDLs (see illustration).

Most doctors don't give a low HDL level the attention it deserves. That's because our cholesterol guidelines emphasize LDL cholesterol, which is much more responsive to treatment. But although raising HDL levels can be difficult, it is possible. And since each 1 mg/dL rise will lower cardiac risk by 2 percent to 3 percent, it is important.

Exercise is a great way to boost HDL levels. On average, sedentary people who start to exercise regularly can expect their HDL levels to rise by 3 percent to 20 percent. The benefit can occur with as little as one mile of walking or jogging a day. But the more you do, the better your result. Brisk walking for 40 minutes a day is a good target, but if you need more help, aim higher. In general, the duration of exercise is more important than the intensity. Any type of moderate exercise is likely to help, as long as you do enough and do it regularly. In some people, the HDL can start to rise after just two months of exercise, but in others it may take two years to see the maximum benefit.

Diet can also make a difference. Just a few years ago, many doctors believed that scaling way back on fat was the best way to improve blood-cholesterol levels. But cutting fat below 16 percent to 22 percent of total calories actually reduces HDL cholesterol levels (although it does lower LDL cholesterol levels). Most guidelines call for a total fat consumption of 25 percent to 35 percent of daily calories. Dietary fat is OK for your good cholesterol -- as long as you eat the right kind of fat.

Saturated fat won't change your HDL cholesterol level, but it will raise your LDL cholesterol. So eat only small amounts of whole-dairy products, red meat and the skin of poultry and avoid palm, palm-kernel and coconut oils, all of which are high in saturated fat. And even without changing your HDL level, avoiding saturated fat can help your good cholesterol do its good work. According to a 2006 study, even one high-fat meal can interfere with the heart-protective function of HDL.

It's even more important to avoid trans-fatty acids, found widely in stick margarine, snack foods, fried foods and commercially baked goods. Trans fat lowers HDL cholesterol and raises LDL cholesterol, a double whammy to health.

Other fats are actually desirable. Virgin olive oil may boost HDL levels, and the omega-3 fats in fish, nuts and canola oil may promote cardiac health even if they don't affect your HDL reading. Remember, though, that all fats are high in calories, and weight control is important for HDL levels and overall health.

Just as with fats, there are good carbohydrates and bad carbohydrates. Diets rich in highly refined carbohydrates (foods made with white flour and white sugar) are clearly linked to low levels of HDL cholesterol. In contrast, unrefined carbohydrates (breads and other products made with whole wheat and other whole grains such as oatmeal, and brown rice) do not depress HDL levels.

Drinking moderate amounts of alcohol (one drink daily for women, two for men) is yet another way to raise HDL. But this recommendation comes with a strong caveat. While a little alcohol is good for the HDL and heart, a lot of alcohol is a killer. People with a history of alcohol abuse should stay away. Even a family history of alcoholism warrants a second thought. The same goes for people with liver disease, uncontrolled hypertension, obesity and depression.

If you're overweight, losing weight can boost HDL. Even if you don't reach an "ideal" weight, rest assured that any weight loss will help. Finally, don't smoke, and don't hang around smokers, either. One study found that just six hours of exposure to environmental smoke lowered HDL cholesterol levels by 18 percent.

If you can make these lifestyle changes, you should be able to nudge your HDL up into the desirable range. It may take some time and diligence, but you'll find that your good cholesterol is great for your health.

Copyright 2007 the President and Fellows of Harvard College. Developed by Harvard Health Publications (www.health.harvard.edu). Distributed by UFS.

Submit questions to harvard_adviser@hms.harva rd.edu.