Multivitamin Supplements

Discovery of the vitamins

Historical reviews describe the discovery of the vitamins as a slow, stepwise process rather than a single breakthrough. A review by Richard Semba places the major period of discovery between the early nineteenth century and the mid-twentieth century. Clinicians came to recognize scurvy, beriberi, rickets, pellagra and xerophthalmia as specific deficiency syndromes, and chemists later isolated the individual vitamins, worked out their structures and developed methods to synthesize them.

The word itself dates to the early twentieth century. A biographical review by Piro and colleagues says Casimir Funk designated these dietary factors 'vitamins' in 1911 and that the scientific community accepted the name in 1912, while Semba dates the coinage to 1912. The two sources differ by a year on this point, and neither supports reading the term as a statement about modern supplement products.

Combined products and the post-war market

The National Institutes of Health Office of Dietary Supplements (ODS) states that people in the United States have taken multivitamin and multivitamin-mineral products since the early 1940s, when the first such products became available. ODS reports that these products are now taken by an estimated one-third of US adults, and that they accounted for about 38 percent of US sales of vitamin and mineral supplements in 2019. The sources reviewed here do not give a detailed history of how the market developed between those points.

Names and scope

ODS uses the abbreviations MVM for multivitamin-mineral products and MV for multivitamins without minerals, and notes informal names such as multis and multiples. It states that these terms have no standard or regulatory definition, so they describe products with widely varying contents. Manufacturers decide the combinations and levels of vitamins, minerals and other ingredients.

Because composition varies, findings from one product do not automatically apply to another. ODS points out that no two randomized trials of these products have used the same combinations and amounts of nutrients, and trial reports typically name the specific product studied.

Related pages on Machipedia

This page is a member of the Machipedia family page named Dietary Supplements, which covers the wider category and is not duplicated here. Related Machipedia pages include Vitamin D Supplementation, Magnesium Supplementation, Omega-3 Fatty Acids, Orthomolecular Medicine, Nutritional Therapy and Dietetics. Single-nutrient products and professional fields are described on those pages, not on this one.

What the products contain

ODS describes several product types, including basic broad-spectrum products taken once a day that contain most vitamins and minerals, most in amounts that do not exceed Daily Values. ODS notes that products often contain small amounts of certain minerals such as calcium, magnesium and potassium, so the product label is the source for what a given product provides. This page does not list products or amounts.

ODS also describes products designed for age, sex or life stage. Formulations for older adults often contain little or no iron and more calcium, vitamin D and vitamin B12 than those for younger adults, and prenatal products generally provide no vitamin A in the form of retinol.

How people use them

ODS reports that people take these products for various reasons, including to increase nutrient intake and to try to improve health or prevent chronic disease. Some users regard a multivitamin as a form of nutritional insurance. ODS also states that, in several studies, users tended to have higher micronutrient intakes from food alone than nonusers, and that populations at highest risk of inadequate intake are the least likely to take these products.

Filling gaps in nutrient intake

ODS states that taking a multivitamin-mineral product increases nutrient intakes and can help people reach recommended amounts of vitamins and minerals when food alone does not provide them. It adds that nutritional needs should be met primarily through the diet, and that supplements may be useful where food cannot meet the needs for specific nutrients, especially at certain life stages.

Prevention of chronic disease

Trial reports describe a widespread perception that multivitamins prevent chronic disease. The Physicians' Health Study II reports described multivitamins as the most common dietary supplement, taken by at least one-third of US adults, and the Women's Health Initiative authors noted that millions of postmenopausal women use them, often believing they prevent cancer and cardiovascular disease. These beliefs are the subject of the trials described in the next section.

Physicians' Health Study II

The Physicians' Health Study II randomized 14,641 male US physicians aged 50 or older to a daily multivitamin or placebo, with a median follow-up of 11.2 years. The cancer report found a statistically significant reduction in total cancer incidence (hazard ratio 0.92, 95 percent confidence interval 0.86 to 0.998), no significant effect on prostate or colorectal cancer, and no significant difference in cancer mortality.

The cardiovascular report from the same trial found no significant effect on major cardiovascular events (hazard ratio 1.01, 0.91 to 1.10), myocardial infarction, stroke, cardiovascular mortality or total mortality. Participants were male physicians, so the results do not directly describe women or other populations.

COSMOS and cognition

The COcoa Supplement and Multivitamin Outcomes Study (COSMOS) randomized older US adults, with a median of 3.6 years of follow-up. ODS summarizes that the multivitamin arm showed no reduction in total invasive cancer or in cardiovascular events, with a lower incidence of lung cancer reported. In the cognition substudy COSMOS-Mind (2,262 participants, mean age 73), Baker and colleagues reported a statistically significant benefit on global cognition (mean z-score 0.07). A related report found no significant reduction in incident mild cognitive impairment or dementia, with low statistical power. A meta-analysis of three COSMOS substudies, including COSMOS-Web, reported small benefits for global cognition and episodic memory. The authors of these reports called for confirmation in more diverse groups.

Observational cohorts

The Women's Health Initiative cohorts followed 161,808 postmenopausal women for a median of about eight years. Multivariate-adjusted analyses found no association between multivitamin use and common cancers, cardiovascular disease or total mortality. ODS notes that most observational studies cannot separate effects of supplements from the healthier habits of people who choose them.

Reviews and task force statements

A Cochrane review by Bjelakovic and colleagues of 78 randomized trials of antioxidant supplements (beta-carotene, vitamins A, C and E, and selenium) found no significant effect on mortality in a random-effects analysis. In 56 trials at low risk of bias, antioxidant supplements significantly increased mortality (relative risk 1.04), with beta-carotene and vitamin E individually associated with higher mortality. This review concerns single and paired antioxidant products, not multivitamins as such.

The US Preventive Services Task Force (USPSTF) statement of June 2022, applying to community-dwelling nonpregnant adults, concluded that evidence is insufficient to assess the balance of benefits and harms of multivitamins for preventing cardiovascular disease or cancer. It recommended against beta-carotene and vitamin E supplements for those purposes.

Evidence limits

ODS states that few randomized trials of these products exist because trials need to be long enough to show effects on disease risk, and that results are mixed. Its fact sheet identifies observational confounding as a central limit. Reports on COSMOS-Mind acknowledge low statistical power for some outcomes and a study population that was mostly non-Hispanic White.

A published editorial position

A 2013 editorial in Annals of Internal Medicine by Guallar, Stranges, Mulrow and colleagues was titled 'Enough is enough: Stop wasting money on vitamin and mineral supplements'. It is an opinion piece rather than a trial, its abstract is not available, and this page cites it only to record that such a position was published; the text of the editorial was not reviewed.

Situations where supplementation is advised

ODS reports that the American College of Obstetricians and Gynecologists recommends a daily prenatal vitamin in pregnancy, that the Dietary Guidelines for Americans state it may be necessary to meet needs for folate or folic acid, iron, iodine and vitamin D, and that the USPSTF advises people planning or capable of pregnancy to take a folic acid supplement. The World Health Organization recommends iron and folic acid supplementation throughout pregnancy.

ODS states that vitamin B12 deficiency is more likely in older adults, people who follow vegetarian diets and infants of women who follow vegan diets, among other groups. For iron, ODS lists infants, young children, teenage girls, and pregnant and premenopausal women as groups at risk of insufficient intake. Whether any individual needs supplementation is a clinical question.

Excess intake and other harms

ODS states that studies of users report no adverse effects beyond minor gastrointestinal complaints, which also occurred in placebo groups. It also states that people who combine these products with other supplements and fortified foods may exceed tolerable upper intake levels for some nutrients, and that this risk is greater for those who also take single-nutrient supplements.

ODS reports that two trials linked supplemental beta-carotene, alone or with vitamin A, to higher lung cancer incidence in smokers, and that the USPSTF warned about this. Preformed vitamin A in excess during pregnancy can increase the risk of birth defects. For iron, ODS identifies hereditary hemochromatosis as a condition with risk of excess iron, and reports that at least 43 US children died between 1983 and 2000 after ingesting high-dose iron supplements. ODS also notes that vitamin K in these products can reduce the effectiveness of warfarin.

Quality, labeling and talking to a clinician

ODS advises that product labels be checked because contents differ, and suggests that consumers consider a product designed for their age, sex and life stage. The ODS consumer guidance recommends discussing with a health care provider, such as a doctor, registered dietitian or pharmacist, whether to take one at all. Supplements are not a substitute for care of a diagnosed deficiency, pregnancy or chronic condition, and questions about medicines, pregnancy, smoking history or iron should go to a clinician.