People who take high doses of vitamin E supplements are at an increased risk of suffering from lung cancer, research suggests. Lead researcher Dr. Christopher G. Slatore of the University of Washington in Seattle studied 77,000 people taking 400 milligrams per day and found its long-term use increased cancer risk by 28 percent.

Over the course of the study, 521 people developed lung cancer. "This risk translates into a 28 percent increased risk of lung cancer at a dose of 400 mg/day for 10 years," wrote Dr. Slatore. Smokers were at particular risk.

Writing in the American Journal of Respiratory and Critical Care Medicine, an expert said people should get their vitamins from natural sources like fruits and vegetable. They also found further that there was an additional 7 percent increase in risk for every 100 milligrams taken per day for over a decade.

Vitamin E is known to be an antioxidant - protecting cells from molecules called free radicals. But experts suggest that in high doses, it may also act as a pro-oxidant, which can cause oxidation and damage to cells.

The best preventive measure to prevent lung cancer is to quit smoking. Anyone who cannot quit should avoid taking beta-carotene supplements, because studies have linked them to an increased risk of lung cancer, the authors added.