Writing last month in the American Journal of Clinical Nutrition, the authors set out to investigate why vitamin E supplementation is more effective at reducing infection in some people than in others.
They noted that the impact of vitamin E on immunity has been shown to be partially mediated by its effect on the production of cytokines, which are proteins that play an important role as signalling agents in assisting the body to maintain immune system function.
“Specific genetic differences at cytokine genes may account for the variable susceptibility to respiratory tract infections (RIs) by influencing the function of immune cells or the cytokine response to pathogens. Given the public health effect of RIs and the potential use of vitamin E as a preventative measure, information on genetic factors that influence the response to vitamin E is needed,” wrote the researchers.
The elderly generally have an increased risk of infection and RIs are common amongst nursing home residents. Using data from a vitamin E intervention in a nursing home, the researchers set out to examine whether the effects of vitamin E on these infections might be partially due to genetic differences at cytokine genes, and whether sex played any part on the interaction.
The trial, which had been conducted between 1998 and 2001, involved 617 participants with an average age of 85. Out of these, 500 participants agreed to DNA tests, and 451 completed the study. The majority were white and female.
Participants were randomly assigned to receive either vitamin E (200 IU all-rac-a-tocopherol) or placebo daily in addition to a multivitamin containing half of the Recommended Dietary Allowance of essential vitamins and minerals, including 4 IU vitamin E.
Blood samples were collected at the start and the end of the trial, and were used to measure clinical chemistries, blood cell differentials, and plasma status for select nutrients including vitamin E.
Nurses also collected information weekly that was related to infection and included respiratory and heart rates and temperature.
In their analysis of the data, the authors of the current study tested if sex, vitamin E and specific DNA sequence variations (single nucleotide polymorphisms (SNPs)) were associated with respiratory tract infections.
After adjusting for other factors that might influence infection rates, the researchers discovered a three-way interaction between vitamin E supplementation, sex and certain genotypes.
“We observed that RIs susceptibility among the elderly may be influenced by SNPs at the IL-2 and IL-10 promoter regions and that the efficacy of vitamin E supplementation for reducing RIs in the aged may depend on sex and IL-10 genotypes,” they wrote.
They said that further studies were needed to verify their findings and understand the mechanisms driving them
“However, our results suggest that the recommendations for vitamin E supplementation as a preventive measure against RIs should consider genetics and sex. These observations may have ramifications for public health through improved predictions of infection in the elderly and help to identify individuals who may benefit the most from taking supplemental vitamin E,” they concluded.
Source: 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
American Journal of Clinical Nutrition, Vol. 92, No. 1, 106-114, July 2010
Authors: Sarah E Belisle, Davidson H Hamer, Lynette S Leka, Gerard E Dallal, Javier Delgado-Lista, Basil C Fine, Paul F Jacques, Jose M Ordovas, and Simin Nikbin Meydani