Multivitamin

Overview
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' highest authority on food standards) as a category of food.

Multivitamin products and components
Many multivitamins are formulated and/or labelled 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 US FDA 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 gene bearing males, 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, B1, B2, B3, B6, folic acid (B9),B12, B5(pantothenate), H (biotin), A, E, D3, K1, potassium iodide, cupric (sulfate anhydrous, picolinate, sulfate monohydrate, trioxide), selenomethionine, borax, 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 K2 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.

Classified as a food, RDA centric multivitamins are not to be confused with the basic orthomolecular medicine daily recommendations. The proponents of that also generally recommend individually optimized, often higher, vitamin intakes. They also recommend more absorbable forms of vitamins and minerals, in inexpensive but higher potency formulas, spread across the day. Often iron-free, fluoride-free formulas, and sometimes copper-free formulas, are preferred.

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. Because high doses of vitamin A are believed to cause birth defects, for example, special multivitamin formulations exist for pregnant women that do not contain this nutrient.

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 bottle related quantites may risk acute overdosage if taken in large amounts, due to the slight toxicity of certain components, principally iron. In particular, other components at extraordinary levels in high potency forms include (but are not limited to) vitamin A, vitamin D, vitamin B6, time release niacin, and potassium. Total iron content of the whole bottle is the primary concern for child safety. 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, conventional medicine and government authorities 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.

Some analyses have suggested that high potency synthetic beta-carotene, vitamin A, and vitamin E supplements, without adequate other redox antioxidants such as vitamin C, may shorten life rather than extend it    in cases of oxidative stress (e.g. smokers), liver disease and liver stressing chemicals (e.g. statins). Other analyses, however, suggest that there appears to be little risk to supplement users of experiencing adverse side effects due to excessive intakes of micronutrients.

Evidence in favor
In 2002, 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, the authors, Robert H. Fletcher and Kathleen M. Fairfield from the Harvard School of Medicine, 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 nutritional supplements. 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."

Similarly, a 2006 report for the United States Department of Health and Human Services concluded that "regular supplementation with a single nutrient or a mixture of nutrients for years has no significant benefits in the primary prevention of cancer, cardiovascular disease, cataract, age-related macular degeneration or cognitive decline." However, the report noted that multivitamins have beneficial effects in people with poor nutritional status, vitamin D and calcium can help prevent fractures in older people, and that zinc and antioxidants can help prevent age-related macular degeneration in people at a high risk of developing this disease.

In 2007 the United Kingdom Food Standards Agency published an updated set of recommendations for eating a healthy diet. The recommendations stated that pregnant women should take extra folic acid and iron and that older people might need extra vitamin D and iron. However, the report advised that "Vitamin and mineral supplements are not a replacement for good eating habits" and stated that supplements are unnecessary for healthy adults who eat a balanced diet.

The United States of America
Because of their categorization as a dietary supplement by the Food and Drug Administration (FDA), most multivitamins sold in the U.S. are not required to undergo the rigorous testing procedures typical of pharmaceutical drugs.

However, some multivitamins contain very high doses of one or several vitamins or minerals, or are specifically intended to treat, cure, or prevent disease, and therefore require a prescription or medicinal license in the U.S. Since such drugs contain no new substances, they do not require the same testing as would be required by a New Drug Application, but were allowed on the market as drugs due to Drug Efficacy Study Implementation program.

Additional Resources

 * Randerson, James. "Vitamin supplements may increase risk of death", The Guardian, April 16, 2008. Accessed April 16, 2008.