Dietary Supplements

Multivitamins and the idea of nutritional insurance

The NIH Office of Dietary Supplements (ODS) reports that people in the United States have taken multivitamin and multimineral products since the early 1940s, when the first such products became available. The same fact sheet states that the concept of a multivitamin as a form of dietary or nutritional insurance was introduced by Miles Laboratories to market its One-A-Day line in the 1940s. The sources reviewed do not describe the history of supplements outside the United States.

A 2022 statement from the US Preventive Services Task Force (USPSTF), citing national survey data, reports that 52% of surveyed US adults used at least one dietary supplement in the prior 30 days and 31% used a multivitamin-mineral product. NCCIH adds that the multivitamin share was 37% in 1999 to 2000 and 31% in 2011 to 2012, so use of that product type fell while overall supplement use stayed common.

Orthomolecular proposals from 1968

The chemist Linus Pauling introduced the term orthomolecular in a 1968 article in Science. Its abstract proposes that providing each person with the optimum concentrations of important normal constituents of the brain may be the preferred treatment for many mentally ill patients. This was a proposal set out in one article and not a test of the idea.

A 2019 editorial by a practitioner describes the field as shaped by the leadership of Abram Hoffer, and lists national orthomolecular societies founded between 1976 and 1994 and the International Society for Orthomolecular Medicine, registered in March 1994. The editorial is written from within the field and is used here only for the organizational timeline.

What the term covers

NCCIH describes dietary supplements as products taken by mouth, such as a tablet, capsule, powder or liquid, that are made to supplement the diet, contain one or more dietary ingredients and are labeled as supplements. Listed ingredients include vitamins, minerals, herbs or other botanicals, amino acids, enzymes, tissues from organs or glands, and extracts of these. ODS adds that products also come as gummies, drinks and energy bars, and names vitamins D and B12, calcium, iron, probiotics and fish oils among popular examples.

How the family differs from food, medicines and herbal medicines

Supplements are concentrated sources of nutrients or other ingredients and not whole foods. ODS states that they cannot take the place of the variety of foods that make up a healthy eating routine, and that the FDA does not determine whether dietary supplements are effective before they are marketed. NCCIH treats herbal supplements, made from plants, algae, fungi or a combination, as one type within the wider group; Machipedia covers plant-based products on its Herbal Medicine page.

Natural origin does not settle how a product behaves in the body. ODS gives comfrey and kava as examples of natural botanical products that can harm the liver, and says safety depends on chemical makeup, how the product works in the body, how it is prepared and the amount taken.

Neighboring Machipedia pages

Several neighboring topics have their own pages. Dietary Approaches, Nutritional Therapy, Dietetics and Nutritional Psychiatry address eating patterns and professional nutrition guidance rather than packaged products. IV Therapy and Vitamin B12 Injections concern nutrients given by infusion or injection instead of by mouth, and DHEA Supplementation covers a separate product. Naturopathy, Apitherapy and Homeopathy are distinct practices or systems that may sit near supplements in the marketplace without being part of this family.

Forms and labels

According to ODS, a Supplement Facts label lists the active ingredients, the amount per serving, and other ingredients such as fillers, binders and flavorings. The manufacturer suggests the serving size, and ODS notes that a health care provider may decide a different amount is more appropriate for a given person. Vitamins and minerals are also added to foods such as breakfast cereals and beverages, so a person may take in more of an ingredient than the supplement alone suggests.

ODS says multivitamin and multimineral supplements have no standard definition of which nutrients they must contain or in what amounts, so the terms cover products with widely varying compositions. It groups them into basic broad-spectrum products taken once a day and other types, including high-potency products.

Quality testing and seals

ODS states that several independent organizations offer quality testing and let products that pass display a seal, and it names ConsumerLab.com, NSF International and U.S. Pharmacopeia (USP) as examples without endorsing them. According to ODS, a seal indicates that the product was properly manufactured, contains the ingredients listed on the label and does not contain harmful levels of contaminants. It adds that the seals do not guarantee a product is safe or effective.

The National Cancer Institute summary on medicinal mushrooms makes a related point about the category: it states that ingredients may vary considerably from lot to lot and that there is no guarantee the ingredients claimed on labels are present, or present in the specified amounts.

Adulteration and mislabeling findings

A 2018 analysis in JAMA Network Open examined supplements that the FDA had flagged between 2007 and 2016. It identified 776 adulterated products and 146 companies; most were marketed for sexual enhancement (45.5%), weight loss (40.9%) or muscle building (11.9%). The most common undeclared drugs were sildenafil, sibutramine and synthetic steroids or steroid-like ingredients, and 20.2% of products held more than one unapproved ingredient. Because it covers flagged products, it does not estimate how common adulteration is across all supplements.

A 2024 analysis of 202 commercially available cannabidiol (CBD) products in the United States found that 74% deviated from their labeled CBD potency by at least 10% and 26% did not meet the product type claimed on the packaging. Heavy metals were detected in 44 products. NCCIH also cautions that some products promoted for weight loss, sexual enhancement and bodybuilding may contain prescription drugs or other ingredients not listed on the label.

Correcting a deficiency versus general wellness

The two purposes make different claims. ODS states that some supplements can help people obtain adequate amounts of essential nutrients when they do not eat a nutritious variety of foods. Its examples include calcium and vitamin D for bone strength, folic acid in lowering the chance of certain birth defects, and a vitamin and mineral combination that may slow further vision loss in people with age-related macular degeneration. ODS says many other supplements need more study to determine whether they have value.

Single-nutrient fact sheets from ODS describe what individual nutrients do: vitamin B12 helps keep blood and nerve cells healthy and helps prevent megaloblastic anemia, iron is used to make hemoglobin, iodine is needed to make thyroid hormones, zinc supports the immune system, and vitamin C is needed to make collagen. ODS advises consulting a health care provider before taking supplements to treat a health condition.

ODS fact sheets on omega-3 fatty acids and magnesium describe them as nutrients or fats with defined roles in the body: the three main omega-3 fatty acids are ALA, EPA and DHA, and magnesium contributes to muscle and nerve function, blood sugar regulation and blood pressure.

Wellness and prevention motives

NCCIH reports that in the 2012 National Health Interview Survey, 89% of adults who used supplements other than vitamins and minerals gave wellness-related reasons: general wellness or disease prevention (83%), improving immune function (42%), improving energy (31%), a focus on the whole person (27%) and improving memory or concentration (22%). The USPSTF notes that the most commonly cited reason for using supplements is overall health and wellness and filling nutrient gaps in the diet.

Some users regard a multivitamin as nutritional insurance. In a cohort of 90,771 adults aged 45 and older described by ODS, multivitamin use raised the share with adequate average intake of 17 nutrients from roughly 72% to 76% up to 83% to 84%, while 10% to 15% of users had excessive intakes of vitamin A, iron and zinc. ODS adds that groups at highest risk of low intake are among the least likely to take multivitamins.

Large trials of vitamin D and omega-3

The VITAL trial randomized 25,871 US adults (men 50 and older, women 55 and older) in a two-by-two design to vitamin D3, marine omega-3 fatty acids or placebo. Over a median 5.3 years, vitamin D was not associated with a lower risk of invasive cancer (hazard ratio 0.96, 95% CI 0.88 to 1.06) or major cardiovascular events (0.97, 0.85 to 1.12). Omega-3 supplementation did not lower major cardiovascular events (0.92, 0.80 to 1.06) or cancer (1.03, 0.93 to 1.13); total myocardial infarction, a secondary endpoint, had a hazard ratio of 0.72 (0.59 to 0.90). The trial tested prevention in generally healthy adults, and its results should not be carried to people with deficiency or established disease.

Multivitamin trials

The Physicians' Health Study II randomized 14,641 male US physicians aged 50 or older to a daily multivitamin or placebo, with a median 11.2 years of follow-up. Total cancer was modestly lower with the multivitamin (hazard ratio 0.92, 95% CI 0.86 to 0.998), with no significant effect on prostate or colorectal cancer. In the companion analysis, major cardiovascular events did not differ (hazard ratio 1.01, 0.91 to 1.10). NCCIH summarizes that most research shows multivitamins do not result in living longer or lower chances of cancer, heart disease or diabetes.

Antioxidant trials and guideline conclusions

A Cochrane review of 78 randomized trials (296,707 participants) of beta-carotene, vitamin A, vitamin C, vitamin E and selenium found no significant effect on mortality in a random-effects model (relative risk 1.02, 95% CI 0.98 to 1.05), but higher mortality in trials at low risk of bias (1.04, 1.01 to 1.07), with beta-carotene and vitamin E associated with the increase. The authors found no evidence to support antioxidant supplements for primary or secondary prevention.

The USPSTF concludes with moderate certainty that harms of beta-carotene outweigh benefits and that vitamin E has no net benefit, and recommends against both for preventing cardiovascular disease or cancer in nonpregnant adults (grade D). It calls the evidence insufficient for multivitamins and for other single or paired nutrients (I statement), meaning the balance of benefits and harms cannot be determined.

Harms reported in trials of specific nutrients

In the Alpha-Tocopherol, Beta-Carotene trial of male Finnish smokers, beta-carotene was associated with an 18% higher lung cancer incidence (95% CI 3% to 36%) and 8% higher total mortality. In SELECT, selenium and vitamin E did not prevent prostate cancer in the 2009 report, and longer follow-up in 2011 found more prostate cancer in the vitamin E group (hazard ratio 1.17, 99% CI 1.004 to 1.36). ODS advises smokers to avoid multivitamin products that provide large amounts of beta-carotene or vitamin A.

ODS states that side effects are most likely at high doses, when supplements replace prescribed medicines, or when many supplements are taken together. It gives examples: too much vitamin A can cause headaches and liver damage, reduce bone strength and cause birth defects, and excess iron causes nausea and vomiting and may damage the liver and other organs.

Interactions with medicines and surgery

ODS notes that supplements can interact with medicines. Vitamin K can reduce the ability of the blood thinner warfarin to prevent clotting, St. John's wort can speed the breakdown of many medicines, and antioxidant supplements such as vitamins C and E might reduce the effectiveness of some chemotherapy. Some supplements can increase bleeding risk or change the response to anesthesia, so ODS advises talking with a health care provider before any surgical procedure.

Pregnancy, breastfeeding and children

ODS advises caution about supplements beyond a standard prenatal supplement during pregnancy or nursing, and care about giving supplements to children unless a health care provider recommends them, because many have not been well tested in these groups. Excess preformed vitamin A in pregnancy can increase the risk of birth defects. NCCIH reports cases of severe or fatal infections in premature infants given probiotics.

Who to ask

ODS recommends telling health care providers, including doctors, dentists, pharmacists and dietitians, about all supplements taken, and keeping a written record of each product, its amount and the reason for use. It advises approval from a health care provider before using supplements in place of or alongside prescribed medicines, and reporting any suspected bad reaction. This page is not a substitute for care, and supplements should not delay or replace necessary medical treatment.

Evidence differs by product

NCCIH notes that the amount of evidence varies widely, with a lot on some supplements and very little on others, and that store-bought products may differ in important ways from those tested in studies. For melatonin, it reports that supplements may help with jet lag, delayed sleep-wake phase disorder and some sleep problems in children, describing the jet lag evidence as based on medium-sized reviews. For probiotics, it states that a benefit shown for one kind of Lactobacillus does not mean another Lactobacillus or any Bifidobacterium would do the same.

Collagen and medicinal mushrooms

A 2026 systematic review of 25 randomized trials of oral hydrolyzed collagen reported improvement over placebo in skin hydration in 10 of 15 trials, elasticity in 10 of 13 and wrinkle measures in 9 of 10, but rated most trials at high risk of bias and called for higher-quality, longer trials. The National Cancer Institute summary on medicinal mushrooms states that clinical trials in cancer patients found Ganoderma lucidum products generally well tolerated. These findings apply to those products and should not be carried to supplements in general.