Supplementation with vitamins or minerals and immune function: can the elderly benefit?

Several measures of immune function have been found to decline with age. The elderly are also at risk for low nutrient intakes, which have been shown to be linked to immune function. This review summarizes human studies on the relationship between immune function measures and vitamin or mineral supplementation. Because of roles in cell proliferation or as anti-oxidants, the primary nutrients studied have been vitamin E, vitamin C, vitamin A, beta-carotene, and zinc. Several randomized controlled trials on vitamin supplementation have been undertaken, with varied study sizes and methodologies. Findings suggest that supplementation with multinutrients can enhance immune function of the elderly. Supplemental zinc and vitamins E, C, A, and beta-carotene may also improve immune function measures, but further research is required. For some nutrients, there is indication that very high doses of supplements are not beneficial with respect to immune function, suggesting an inverted U-shaped relationship. Further research in this area should include the nutritional status of the population prior to randomization, and immunity-related health outcomes, such as infection rates. (C) 2003 Elsevier Inc. All rights reserved.