Efficacy of vitamin E in preventing respiratory tract infection may be genotype-dependent

Genetics might influence the magnitude of an individual immune response to vitamin E supplementation in respiratory tract infections, says a new US study.

In the study, data from a previous randomized controlled trial were used: 617 elderly nursing home residents (mean: 84.6 years) were allocated to receive either vitamin E (200 IU alpha-tocopherol) or a placebo daily for one year (1). Based on blood samples, physical examinations and interviews, the incidence and duration of respiratory infections were assessed. While vitamin E supplementation had no significant effect on incidence or number of days with total (upper and lower) infections, the researchers observed a protective effect on upper respiratory tract infections, particularly the common cold, in some subgroups of the elderly population. To examine whether the effect of vitamin E on respiratory infections was dependent on genetic backgrounds, the researchers analyzed the DNA of 500 participants in the new study (2). The results showed that the effect of vitamin E was influenced by the sex of the participant and genetic factors: genetic variations (so called polymorphisms) at immunoregulatory genes seem to contribute to individual risk of respiratory infections.

References:The scientists commented that the recommendations for vitamin E supplementation as a preventive measure against respiratory infections should consider genetics and sex. They hypothesized that differences in individual genetics could help explain some of the large-scale intervention trials which have not demonstrated a health benefit to vitamin E supplementation. However, further studies would be needed to verify the results and understand the mechanisms driving them, they concluded.

1. Meydani S.N. et al. Vitamin E and respiratory tract infections in elderly nursing home residents: a randomized controlled trial. JAMA. 2004; 292:828–36.
2. Belisle S.E. et al. IL-2 and IL-10 gene polymorphisms are associated with respiratory tract infection and may modulate the effect of vitamin E on lower respiratory tract infections in elderly nursing home residents. Am J Clin Nutr. 2010; 92:106–14.