Micronutrients and Immunity in Older People

Key Points Placebo-controlled clinical trials, despite their limitations, are the best approach for studying effects of micronutrients on immunity. High doses of some single nutrients may improve immunity in relatively short time periods (weeks to months), but persistence of these effects is not currently known. High doses of other micronutrients may adversely affect immunity. Some micronutrients may interfere with the beneficial effects of other micronutrients on immunity; this effect depends on relative doses. Low- to moderate-dose multivitamin/mineral supplements may require considerable time (6 mo to 1 yr or more) before they enhance immune functions and potentially reduce susceptibility to infectious diseases, and the timing of their effects may differ between men and women. High- and even low-dose micronutrient supplements may enhance immunity even in the absence of evidence of underlying deficiencies. Micronutrient supplements are not a substitute for a good diet and regular exercise but, rather, are a complementary measure. Long-term ingestion of single nutrient supplements, especially at high doses, may have beneficial and/or adverse effects on immunity and other outcomes.