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Designed for people whose diets don’t meet all of their nutritional needs, multiple vitamin–mineral supplements (“multivitamins”) are convenient nutrient combinations, usually taken one to six times per day. While it’s generally agreed that a healthy diet is the best foundation for health, everyday life makes that goal challenging for many people. So, some people supplement in hope of preventing disease-causing deficiencies and providing higher nutrient amounts than they can get through diet alone, which may help prevent or manage certain diseases.
Recommended dietary allowances (RDAs) have been developed by a scientific panel to broadly cover healthy people of any age or gender. Used to design mass food programs, such as for the armed forces and food relief/ration programs, RDA’s were the basis for the Reference Daily Intake (RDI) values, which the US Food and Drug Administration (FDA) uses to create the Daily Value (DV) packaging labels.
Many multivitamins contain at least 100% of RDA recommendations. However, decades of research on human nutrition has led many researchers and healthcare professionals to conclude that a “one-size-fits-all” approach does not address the increased need for certain nutrients by people who are not healthy or by those at increased risk of developing various diseases due to genetics or lifestyle habits. The RDA does account for this increased need in certain cases such as, vitamin C for smokers, or vitamin D for seniors. Abundant research also suggests therapeutic benefits to supplementing with certain nutrients, even when eating a healthful diet.
For a list of the recommended optimal amounts of each nutrient, go to a Healthy Person's Guide to Vitamins & Minerals.
Multivitamins are available as a powder inside a hard-shell pull-apart capsule, as a liquid inside a soft-gelatin capsule, or hard-pressed as tablets that may be chewed or swallowed. Common products on the market include:
The best time to take most supplements is with meals, to avoid stomach upset they sometimes cause and to help the body better absorb the nutrients.
Nothing beats a nutrient-rich, whole foods diet as a foundation for good nutrition, and quality supplements may help support that goal.
While a whole food diet is the preferable route, a high-quality multivitamin might be recommended for children eating an unbalanced diet. In one double-blind trial, schoolchildren received a daily low-potency vitamin-mineral tablet for three months that contained 50% of the RDA for most essential vitamins and the minerals. About 20% of participants (working class, primarily Hispanic, children, aged 6 to 12) experienced dramatic gains in certain measures of IQ, possibly due to correction of specific nutrient deficiencies in these children. However, it was not possible in this study to identify which nutrients caused the improvement.