The Exercise-Cholesterol Link
Researchers aren't entirely sure how exercise lowers cholesterol, but they are beginning to have a clearer idea. "Lots of people, even lots of doctors, assume that exercise lowers cholesterol," says Amit Khera, MD, director of the University of Texas, Southwestern, Medical Center's Program in Preventive Cardiology. "But until recently, most of us weren't sure just what the connection was."
One way exercise can help lower cholesterol is by helping you lose -- or maintain -- weight. Being overweight tends to increase the amount of low-density lipoprotein (LDL) in your blood, the kind of lipoprotein that's been linked to heart disease.
Part of the confusion about the effect of exercise on cholesterol stems from the fact that most early cholesterol studies focused on both exercise and dietary changes, making it hard to tease out which of these factors was actually making the difference. But recent studies have more carefully examined the effect of exercise alone, making it easier to evaluate the relationship between exercise and cholesterol.
Researchers now believe there are several mechanisms involved. First, exercise stimulates enzymes that help move LDL from the blood (and blood-vessel walls) to the liver. From there, the cholesterol is converted into bile (for digestion) or excreted. So the more you exercise, the more LDL your body expels.
Second, exercise increases the size of the protein particles that carry cholesterol through the blood. (The combination of protein particles and cholesterol are called "lipoproteins;" it's the LDLs that have been linked to heart disease). Some of those particles are small and dense; some are big and fluffy. "The small, dense particles are more dangerous than the big, fluffy ones because the smaller ones can squeeze into the [linings of the heart and blood vessels] and set up shop there," says Khera. "But now it appears that exercise increases the size of the protein particles that carry both good and bad lipoproteins."
How Much Exercise Does It Take To Lower Cholesterol?
Exactly how much exercise is needed to lower cholesterol has been a matter of some debate. In general, most public health organizations recommend, at a minimum, 30 minutes per day of moderate to vigorous exercise , such as walking, jogging, biking, or gardening.
But a 2002 study by researchers at Duke University Medical Center found that more intense exercise is actually better than moderate exercise for lowering cholesterol. In a study of overweight, sedentary people who did not change their diet, the researchers found that those who got moderate exercise (the equivalent of 12 miles of walking or jogging per week) did lower their LDL level somewhat. But the people who did more vigorous exercise (the equivalent of 20 miles of jogging a week) lowered it even more.
The people who exercised vigorously also raised their levels of high-density lipoprotein (HDL) -- the "good" kind of lipoprotein that actually helps clear cholesterol from the blood. "We found it requires a good amount of high intensity exercise to significantly change HDL," saysWilliam Kraus, MD, an assistant professor of medicine at Duke and the lead author on the study. "Just walking is not enough."
According to Kraus's findings, however, even though moderate exercise was not as effective in reducing LDL or increasing HDL, it did keep cholesterol levels from rising.
Bottom line? Some exercise is better than none; more exercise is better than some.
How Much Will It Help?
Just how much of an effect exercise has on cholesterol is also a matter of debate. "We've found that the people who benefit the most are those who had the worst diet and exercise habits to begin with," says Roger Blumenthal, MD, director of the Ciccarone Preventive Cardiology Center at Johns Hopkins University. "Some of those people reduce their LDL by 10-15% and increase their HDL by 20%."
If you haven't been exercising regularly already, it's important to start slowly. Be sure to check in with your doctor, so that he or she can evaluate your current cardiovascular health. This could mean blood tests or a treadmill test to see how your heart reacts when you exercise.)
Once you're cleared to begin working out, follow these guidelines:
- Choose a form of exercise you can do for 10-20 minutes at a time, with at least moderate intensity, such as walking, biking, swimming, jogging, or using an exercise machine at low speed).
- Know that while the intensity may be moderate, the "exercise volume," which means the amount of time you spend exercising, has to be pretty high. The American Heart Association recommends working up to 30 minutes of physical activity per day, or 60 minutes per day if you're also trying to lose weight. Remember: you can get your exercise in 10 minutes increments if need be, as long as it adds up to 30 minutes by the end of the day.
- Find an activity you love, whether it's walking your dog, playing tag with your kids, swimming laps at a pool, or bicycling through your community. Finding a buddy to exercise with can be helpful, too, both for moral support and to help make exercise more enjoyable.
- Even better, find several activities you love, so you can vary your routine. This helps you exercise more than one set of muscles, as well as enjoying different work-out environments.
Of course, exercise alone won't guarantee a low cholesterol level. Genetics, weight, age, gender, and diet all contribute to an individual's cholesterol profile. The most effective way to ensure a healthy cholesterol level is to modify your diet and, if need be, take cholesterol-lowering medications.
But exercise has many advantages beyond lowering cholesterol. Exercise has been shown to keep bones strong, reduce the risk of cancer, diabetes, stroke, and obesity, and to improve mood. "Even if the improvements in your cholesterol profile are modest, there are many, many other benefits," says Blumenthal.