Vitamin E use may raise tuberculosis risk in heavy smokers

NEW YORK (Reuters Health) - The use of vitamin E supplements appears to increase the risk of tuberculosis in some middle-aged smokers, according to a study in the British Journal of Nutrition.

In the overall analysis, vitamin E use did not affect the odds of tuberculosis in smokers. In people who smoked at least 20 cigarettes per day and consumed diets high in vitamin C, however, vitamin E supplements more than doubled the risk.

Vitamin E is a widely used dietary supplement believed to enhance immune function, note authors Dr. Harri Hemila and Dr. Jaakko Kaprio. However, trials in human subjects have shown unpredictable effects of vitamin E on various infectious diseases.

To examine the impact of vitamin E use on the risk of tuberculosis, the two researchers from the University of Helsinki in Finland analyzed data from the ATBC (Alpha-Tocopherol, Beta-Carotene Cancer Prevention) Study.

The study participants were 29,023 male smokers, ages 50 to 69 years, who were randomly assigned to take daily supplements containing vitamin E, beta-carotene, vitamin E plus beta-carotene, or inactive placebo.

During a follow-up period of around 6 years, 174 cases of tuberculosis were diagnosed. Overall, neither vitamin E nor beta-carotene supplements affected the risk of tuberculosis.

However, as noted, the combination of smoking 20 or more cigarettes per day and consuming a diet rich in vitamin C and vitamin E supplements more than doubled the risk of tuberculosis. Further analysis showed that the increased risk was restricted to the first year after vitamin E supplementation began.

"Although vitamin E may be beneficial in restricted population groups, those groups are poorly defined so far," Hemila and Kaprio point out.

"The consumption of vitamin E supplements by the general population should be discouraged because there is evidence of harm for some people," they conclude.

SOURCE: British Journal of Nutrition, online February 18, 2008.