A multivitamin is a preparation intended to supplement a human diet with vitamins, dietary minerals and other nutritional elements. Such preparations are available in the form of tablets, capsules, pastilles, powders, liquids and injectable formulations. Other than injectable formulations, which are only available and administered under medical supervision, multivitamins are recognized by the Codex Alimentarius Commission (the United Nations' authority on food standards) as a category of food. Multivitamin supplements are commonly provided in combination with minerals. A multivitamin/mineral supplement is defined in the United States as a supplement containing 3 or more vitamins and minerals but does not include herbs, hormones, or drugs, with each nutrient at a dose below the tolerable upper level determined by the Food and Drug Board and the maximum daily intake to not cause a risk for adverse health effects.
The terms multivitamin and multimineral are often used interchangeably. There is no scientific definition for either. Linguistically, the terms are compounded words of which meaning can be derived in that capacity.
History
Multivitamin-multimineral products providing more than vitamins A and D became available in pharmacies and grocery stores in the mid-1930s. In 1934 Nutrilite Company introduced the first multivitamin-multimineral tablets. These supplements were made from natural dried and compressed vegetable and fruit concentrates. In the early 1940s other brands started to produce synthetic tablets.
Multivitamin products and components
Many multivitamins are formulated and/or labeled to differentiate consumer sectors e.g. prenatal, children, mature or 50+, men's, women's, diabetic, stress or megavitamin. Consumer multivitamin formulas are available as tablets, capsules, bulk powder, or liquid. Once and twice per day multivitamin formulas dominate common usage, although some formulas are designed for consumption 3–7 times per day or even allow hourly use.
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. Legally, the United States Food and Drug Administration allows a multivitamin to be called "high potency" if at least two-thirds of its nutrients have at least 100 percent of the DV. In practice, "high potency" usually means substantially increased vitamin C and Bs with some other enhanced vitamin and mineral levels, but some minerals may still be much less than DV.
Some components are typically much lower than RDA amounts, often for cost reasons, e.g. biotin, usually the most expensive vitamin component, at over $4000 per active pound, is typically added in at only 5%-30% of RDA in many one per day formulations. Sometimes low content composition is for population subgroups, where the RDA would be inappropriate, such often occurs with iron, where the original population intake calculation was ca 12–13 mg iron per day by including menstruating females but some percentage of HFE variant gene bearing males with high iron retention, and others, may only need as little as ~1 mg iron per day including the normal dietary contribution.
Basic commercial multivitamin supplement products often contain the following ingredients: vitamin C, B 1 , B 2 , B 3 , B 6 , folic acid (B 9 ), B 12 , B 5 (pantothenate), H (biotin), A, E, D 3 , K 1 , potassium iodide, cupric (sulfate anhydrous, picolinate, sulfate monohydrate, trioxide), selenomethionine, borate(s), zinc, calcium, magnesium, chromium, manganese, molybdenum, betacarotene, and iron. Other formulas may include additional ingredients such as other carotenes (e.g. lutein, lycopene), higher than RDA amounts of B, C or E vitamins including gamma-tocopherol, "near" B vitamins (inositol, choline, PABA), trimethylglycine (anhydrous betaine), betaine hydrochloride, vitamin K 2 as menaquinone-7, lecithin, citrus bioflavinoids or nutrient forms variously described as more easily absorbable.
Uses
By supplementing the diet with additional vitamins and minerals, multivitamins can be a valuable tool for those with dietary imbalances or different nutritional needs. People with dietary imbalances may include those on restrictive diets and those who can't or won't eat a nutritious diet. Pregnant women and elderly adults have different nutritional needs than other adults, and a multivitamin may be indicated by their physicians.
The proponents of orthomolecular medicine recommend individually optimized vitamin intakes, usually at higher doses than standard recommendations (such as the US RDA). They also recommend more absorbable forms of vitamins and minerals, in inexpensive but higher potency formulas, spread across the day.
Precautions
While multivitamins can be a valuable tool to correct dietary imbalances, 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 analyses 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.
Severe vitamin and mineral deficiencies require medical treatment and can be very difficult to treat with common over-the-counter multivitamins. In such situations, special vitamin or mineral forms with much higher potencies are available, either as individual components or as specialized formulations, sometimes requiring a prescription.
Multivitamins in large quantities may pose a risk of an acute overdose, due to the toxicity of some components, principally iron. However, in contrast to iron tablets, which can be lethal to children, toxicity from overdoses of multivitamins are very rare. There appears to be little risk to supplement users of experiencing acute side effects due to excessive intakes of micronutrients. There also are strict limits on the retinol content for vitamin A during pregnancies that are specifically addressed by prenatal formulas. Additionally, various medical conditions and medications may adversely interact with multivitamins.
For normal adults taking a multivitamin for general health purposes, it is recommend that a multivitamin should contain 100% DRI/RDA or less for each ingredient. However, many common brand supplements in the United States contain above-DRI amounts for some vitamins or minerals. Many brands offer low iron or iron-free versions of their multivitamin supplements.
Scientific assessment
Evidence in favor
In 2002, a paper by Robert H. Fletcher and Kathleen M. Fairfield from the Harvard School of Medicine, in the Journal of the American Medical Association stated that "it appears prudent for all adults to take vitamin supplements." In this article, which examined the clinical applications of vitamins for the prevention of chronic diseases in adults examined English-language articles about vitamins in relation to chronic diseases published between 1966 and 2002, and concluded that inadequate intake of several vitamins has been linked to the development of diseases including coronary heart disease, cancer, and osteoporosis.
Similarly, the April 9, 1998 issue of the New England Journal of Medicine featured an editorial entitled "Eat Right and Take a Multivitamin" that was based on studies that showed health benefits resulting from the consumption of supplemental folate to prevent birth defects and possibly decrease the incidence of cardiovascular disease.
Bruce Ames, professor of Biochemistry and Molecular Biology at the University of California, Berkeley, and a senior scientist at Children's Hospital Oakland Research Institute (CHORI), suggests that "to maximize human health and lifespan, scientists must abandon outdated models of micronutrients" and that "a metabolic tune-up through an improved supply of micronutrients is likely to have great health benefits."
Evidence against
In 2006 the National Institutes of Health convened an expert panel to examine the available evidence on nutrient supplements. This review concluded that "Most of the studies we examined do not provide strong evidence for beneficial health-related effects of supplements taken singly, in pairs, or in combinations of three or more." They noted that multivitamins could provide health benefits to some groups of people, such as postmenopausal women, but that there was "disturbing evidence of risk" in other groups, such as smokers. The panel's report concluded that the "present evidence is insufficient to recommend either for or against the use of Multivitamin/Mineral Supplements by the American public to prevent chronic disease."
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