In the past, experts claimed that if people ate healthy diets, taking vitamins was not necessary. However, research is now showing that it is beneficial for the majority of adults to take a multivitamin each day.   The purpose of this summary is to offer information on why people should take multivitamins, how to improve your diet to increase vitamin intake, and to show newly suspected or acknowledged roles of certain vitamins in health and disease prevention.

Multivitamin ingredients are measured in terms of the Daily Value (DV). This recommended amount of each vitamin and mineral is established by the U.S. Food and Drug Administration (FDA), and is based in part on the Recommended Dietary Allowances (RDA). Experts say that you should look for a multivitamin that provides 100% of the DV for most of the essential vitamins and minerals in one pill. The exception is calcium, which is too large to fit in one pill, but which can easily be consumed through diet or additional supplements.

Compositional variation amongst brands and lines allows substantial consumer choices. Modern multivitamin products roughly classify into RDA centric multivitamins with or without iron, RDA centric multivitamin/multimineral formulas with or without iron, higher potency formulas with mostly above RDA components with or without iron, and more specialized formulas by condition, such as for diabetics or by less common components, such as diversified antioxidants, herbal extracts or premium vitamin and mineral forms.

It is worth exercising basic caution before taking them, especially if any medical conditions exist. In particular, pregnant women should generally consult their doctors before taking any multivitamins: for example, either an excess or deficiency of vitamin A can cause birth defects.[ Some analyzes have suggested that long-term use of beta-carotene, vitamin A, and vitamin E supplements may shorten life rather than extend it, with the additional risk being particularly large in smokers.

In conclusion the evidence for routine use of multivitamin and mineral supplements to reduce infections in elderly people is weak and conflicting. Study results are heterogeneous, and this is partially confounded by outcome measure.