DALLAS, July 10 -- Researchers have shown that long-term exercise may help fight atherosclerosis, the disease process that obstructs blood vessels and triggers heart attacks and strokes.
A study in this month's Arteriosclerosis, Thrombosis and Vascular Biology: Journal of the American Heart Association suggests that cardiovascular benefits of exercise are more evident in long-term exercisers than in people who are physically active in spurts or for short periods of time.
Sampath Parthasarathy, Ph.D., lead author of the paper, conducted the study to determine how exercise could help the body. Exercise increases the blood and tissue levels of free radicals, highly reactive oxygen molecules that oxidize the "bad" form of cholesterol (low-density lipoprotein or LDL), making it more dangerous to blood vessels.
"Either the benefits outweigh the bad effects of oxidation or the fact that exercise is an oxidative stress is itself part of the beneficial package," says Parthasarathy, of Emory University School of Medicine in Atlanta.
Parthasarathy explains that what actually happens is similar to an immune response to a vaccine. In blood tests of long-term exercisers, Parthasarathy found that LDL in the blood was protected from oxidation because the body had built up an antioxidant defense. In short-term exercisers -- students who had just begun an exercise class -- this antioxidant defense was absent, and their LDL was actually more easily oxidized.
This doesn't mean that the short-term exercisers were without any benefit, says Parthasarathy. The study suggests that while short-term exercise increases LDL oxidation, it promotes the oxidation of LDL in the blood where the liver can rapidly filter it out, rather than in the blood vessels, where it can lead to atherosclerosis. To help reduce LDL oxidation, the American Heart Association also recommends a nutritionally balanced, low-saturated fat, low-cholesterol diet including a variety of fruits and vegetables. Co-authors are Robin Shern-Brewer, Ph.D., Nalini Santanam, Ph.D., Carla Wetzstein, Ph.D., and Jill White-Welkley, Ph.D.
NR 98-4924 (Arterio/Parthasarathy)
Media advisory: Dr. Parthasarathy can be reached by phone at (404)
727-8604. (Please do not publish number.)