Vitamin E supplementation may decrease or increase, or may have no effect, on the risk of pneumonia depending on the level of smoking and leisure time exercise, according to a study.
In laboratory studies, vitamin E has influenced the immune system. In several animal studies vitamin E protected against viral and bacterial infections. However, the importance of vitamin E on human infections is not known.
Dr. Harri Hemila and Professor Jaakko Kaprio, of the University of Helsinki, Finland, studied the effect of vitamin E on the risk of pneumonia in the large randomized trial (Alpha-Tocopherol Beta-Carotene Cancer Prevention Study), which was conducted in Finland between 1985-1993. There were 898 cases of pneumonia among 29,133 participants of the study.
Vitamin E had no overall effect on pneumonia risk. However, vitamin E decreased pneumonia risk by 69 percent among participants who had the least exposure to smoking and exercised during leisure time. In contrast, vitamin E increased pneumonia risk by 79 percent among those who had the highest exposure to smoking and did not exercise.
Over half of the participants were outside of these two subgroups and vitamin E did not affect their risk of pneumonia. Thus, the beneficial and harmful effects of vitamin E are restricted to fairly small parts of the population.
The researchers concluded the role of vitamin E in susceptibility to pneumonia in physically active nonsmokers warrants further study.
The study has been published in Clinical Epidemiology.