Micronutrient Supplements May Not Stave Off Respiratory Infection

WAGENINGEN, The Netherlands--Neither daily multivitamin/mineral supplementation nor 200 mg/d of vitamin E was shown to improve the incidence or severity of respiratory tract infections in free-living elderly subjects, according to research published in the Aug. 14 issue of the Journal of the American Medical Association (288, 6:715-21, 2002) (www.jama.com). Researchers from Wageningen University randomly assigned 652 elderly subjects (aged 60 years or older) to receive either a multivitamin/mineral supplement, vitamin E (200 mg/d), both or placebo.

Researchers began with the hypothesis that immune response can be improved in elderly subjects with micronutrient supplements, although not enough trials have evaluated this effect against infectious disease. For a period of just over a year (63 weeks), researchers recorded the incidence, symptoms and severity of respiratory tract infections in their study population. After the observation period, researchers did not see a significant difference between the groups in the incidence of infections. More than half of the participants (68 percent) reported a total of 1,024 respiratory tract infections, with no significant differences shown between supplement groups compared with the placebo group.

Infection severity was not affected by supplementation either, according to researchers, who stated subjects in the vitamin E group reported worse symptom severity than subjects in the placebo group. The vitamin E group reported a median 19-day duration for infections, compared to 14 days in the placebo group. Additionally, 36.7 percent of the vitamin E group reported fever compared to 25.2 percent of the placebo group, and 52.3 percent of the vitamin E group cited reduced activity compared to 41.1 percent of the placebo group. Researchers concluded neither multivitamin/mineral supplementation nor vitamin E supplementation had a beneficial effect on the incidence or severity of respiratory tract infections in well-nourished elderly subjects.

Prior research has indicated vitamin E may be useful for staving off influenza, mainly due to its immune-enhancing activity. A group of researchers from the Jean Mayer Human Nutrition Research Center on Aging conducted animal research and determined that vitamin E supplementation protected against influenza infection in aged mice (Proc Nutr Soc, 58, 3:697-705, 1999). The same researchers reported a year later that vitamin E's ability to improve immune activity in the presence of an influenza virus is due to a boost in the production of helper T-cells--which, among other things, tell cytotoxic T-cells when to attack infection (Immunology, 100, 4:487-93, 2000). Vitamin E has also been shown to improve T-cell ratios--which would act to balance the attack/suppress behavior of cytotoxic T-cells and suppressor T-cells--in humans with colorectal cancer, according to researchers from the Karolinska Institutet in Stockholm, Sweden (Clin Cancer Res, 8, 6:1772-8, 2002).