Exercise Combats Cholesterol, Study Says
Consistent exercise may teach the body how to fight off buildups of a form of cholesterol that can lead to clogged arteries, a study finds.
Long-term exercisers seem to have a way to keep low-density lipoprotein cholesterol, LDL, from turning into deposits that eventually can result in reduced blood flow or artery-blocking clots, according to researchers at Emory University School of Medicine in Atlanta.
Exercise apparently changes the way in which the body handles free radicals, highly reactive oxygen molecules that encourage LDL particles to form the deposits, according to researcher Sampath Parthasarathy.
The study was an attempt to resolve a paradox. Aerobic exercise, which requires the body to use more oxygen, raises levels of free radicals. Yet exercisers have a reduced risk of heart disease.
“At present, oxidation is suggested to be a detrimental factor, and anti-oxidants are said to be beneficial,” Parthasarathy said. “How can an oxidative stress be beneficial in preventing heart disease?”
The experiments were reported in an American Heart Assn. journal, Arteriosclerosis, Thrombosis and Vascular Biology.
In the first part of the research, blood samples from nine students who did not exercise were compared with samples from eight students who had completed a six-week exercise program. LDL in the blood of the beginning exercisers was more easily oxidized, Parthasarathy said.
But the exercisers in this preliminary study were predominantly male and the sedentary controls were predominantly female. This raised a question about whether the results were sex-related. So when the researchers moved on to a larger follow-up study, they had men and women evenly in both exercise and non-exercise groups.
In the second study, blood samples were taken from 30 regular exercisers--members of Emory teams including basketball, volleyball and track. Samples were also taken from 33 non-exercisers.
This time, the results were reversed--the LDL of male exercisers was harder to oxidize than was the blood of their sedentary counterparts.
Women exercisers and non-exercisers had about the same difficulty in oxidizing LDL--higher than the non-exercising men, but lower than the male exercisers, the study found. The research did not explain the male-female difference, but Parthasarathy suspected the female hormone estrogen--which protects against heart disease--plays a role.
Parthasarathy concluded that the additional oxygen that the body takes in during regular exercise over a course of months somehow trains it to fight off the oxidizing effect on LDL.
As for beginning exercisers, Parthasarathy suggested they take vitamin E supplements. Vitamin E, an antioxidant, fights the troublesome free radicals.
Other research has indicated how exercise may fight the free radicals, said Steve Farrell, associate director of the Cooper Institute for Aerobics Research in Dallas. “There is some evidence that [regular] exercise increases enzymes that neutralize the free radicals,” he said. “That’s pretty well accepted.”
And the study adds to the evidence that exercise reduces heart disease risk, Farrell said.
The study’s findings seem sound, said lipid researcher G. Russell Warnick of Seattle. “It sounds intriguing, and it makes sense--and, as a runner, I hope it’s true,” said Warnick, formerly chief scientific officer and now consultant with Pacific Biometrics, a diagnostic technology company.
The study is not the last word, Warnick said.
“The issue is that the oxidation process is complicated and not well understood,” he said. “It’s so difficult to do these types of studies. You have to do them several times from different angles until it becomes clear.”
