Do You Need a Multivitamin? What the Big Trials Show

A multivitamin is one daily pill with many vitamins and, usually, minerals. About a third of US adults take one: 31% reported using a multivitamin-mineral supplement in a national survey (USPSTF 2022). This guide covers adults and what the largest trials found.

The short version

• Heart disease: no fewer heart attacks, strokes or heart deaths in two large trials of older adults. A Grade A (Sesso 2012; Sesso 2022).
• Living longer: no effect on deaths from any cause across 21 pooled trial reports (91,074 people). A Grade A (Macpherson 2013).
• Cancer: 8% fewer cancers in one large trial of male doctors, no clear drop in the other. B Grade B, mixed (Gaziano 2012; Sesso 2022).
• Memory in older adults: slightly better scores when three sub-studies of one trial were pooled, but no gain in another large trial. B Grade B (Vyas 2024; Grodstein 2013).
• High-dose beta-carotene in smokers: more lung cancer in two large trials. A Grade A for harm (ATBC 1994; Omenn 1996).

Do multivitamins prevent heart disease?

A Grade A: no. In the Physicians' Health Study II (PHS II), 14,641 US male doctors aged 50 or older took a common daily multivitamin or placebo for a median of 11.2 years. Major heart events (heart attack, stroke or heart death, the main outcome) were no different (hazard ratio 1.01) (Sesso 2012). In COSMOS, 21,442 US adults (women 65 and older, men 60 and older) were randomized to a multivitamin-mineral or placebo each day; after a median of 3.6 years, heart disease events were again no different (hazard ratio 0.98) (Sesso 2022). Our multivitamin page grades these no-effect findings D; two trials this large and consistent support A.

Do multivitamins lower cancer risk?

B Grade B, mixed. In PHS II, total cancer, the main outcome, was 8% lower on the multivitamin (hazard ratio 0.92, a result just inside statistical significance), while prostate and colorectal cancers did not change and cancer deaths showed no clear difference (Gaziano 2012). In COSMOS, total invasive cancer, its main outcome, was no different (hazard ratio 0.97); lung cancer, one of its secondary outcomes, was lower (hazard ratio 0.62) (Sesso 2022). The US Preventive Services Task Force (USPSTF) judged the evidence insufficient to recommend multivitamins for preventing heart disease or cancer (USPSTF 2022; USPSTF 2022 summary).

Do multivitamins help you live longer?

A Grade A: no. Pooling 21 trial reports (91,074 people, average age 62), multivitamin-minerals did not change deaths from any cause (risk ratio 0.98), from heart disease or from cancer (Macpherson 2013). Neither PHS II nor COSMOS found a clear drop in deaths (Sesso 2012; Sesso 2022). Across three US cohorts (390,124 adults, follow-up as long as 27 years), daily users had a slightly higher death rate than non-users in the first half of follow-up (hazard ratio 1.04), not a lower one; an observational study like this can't prove cause (Loftfield 2024).

Do multivitamins help memory in older adults?

B Grade B: a small gain in one trial program. COSMOS ran three memory sub-studies. In a telephone-tested trial of 2,262 people (average age 73), those on a multivitamin did better on global cognition over 3 years, a pre-specified secondary outcome, and on memory and executive function (Baker 2023). In an online trial of 3,562 people, the multivitamin group did better on immediate word recall at 1 year, the main outcome, but not on secondary outcomes (Yeung 2023). Pooling all three sub-studies, the gain in global cognition (0.07 standard units) equalled about 2 years less cognitive aging (Vyas 2024). New cases of mild cognitive impairment or dementia did not fall over 3 years, though the study had little power to show it (Sachs 2023).

In a PHS II study of 5,947 male doctors aged 65 or older, a multivitamin for up to 12 years made no difference in thinking or verbal memory (Grodstein 2013). Our multivitamin page shows D for memory and thinking; the COSMOS sub-studies and their pooled analysis support B, with PHS II as the counterweight. See supplements for memory and brain fog.

Do multivitamins help energy, immunity, eyes or hair?

• Infections: grade B, no clear benefit. Across 8 trials in older people, multivitamins cut days with infection in 3 trials but not the number of people who got an infection (odds ratio 1.10, 3 trials) (El-Kadiki 2005). In 910 adults aged 65 or older living at home, a year of multivitamins did not change infections or doctor visits (Avenell 2005).
• Stress and tiredness: grade B, small. Pooling 8 placebo-controlled trials in healthy people taking supplements for at least 28 days, perceived stress, anxiety and fatigue fell slightly; depression did not (Long 2013).
• Cataracts: grade C. In PHS II, cataracts were 9% less common (hazard ratio 0.91), with no effect on macular degeneration (hazard ratio 1.19, not significant) (Christen 2014).
• Hair: no trial has tested an ordinary multivitamin for hair loss. See supplements for hair loss.

Who may need a multivitamin?

A multivitamin isn't the only way to fill a gap, and often a single nutrient fits better. These groups have a real reason to ask:

• Adults over 50: older stomachs absorb vitamin B12 from food less well; atrophic gastritis, which cuts B12 absorption, affects 8% to 9% of adults 65 and older (NIH ODS). See vitamin B12 for energy and, on metformin, does metformin lower vitamin B12?
• Vegans: natural B12 comes only from animal foods, so vegans need fortified foods or a supplement (NIH ODS; Guéant 2022).
• Pregnant or planning a pregnancy: folic acid matters most; see prenatal supplements.
• After weight-loss (bariatric) surgery: your surgical team sets your supplements; a US surgical society's guideline has 92 recommendations on vitamins and minerals alone (Parrott 2017).
• On a GLP-1 medicine and eating much less: see supplements on GLP-1 medicines.
• Heavy periods: iron is the usual gap; test first. See iron supplements.
• Pregnancy, older age and poor absorption: iodine in pregnancy and vitamin D for some older adults are common single-nutrient gaps, as are deficiencies in people with conditions that cut absorption, such as coeliac or Crohn's disease; take them as your clinician advises (NIH ODS: iodine; NIH ODS: vitamin D).

Which vitamins are risky in high doses?

Beta-carotene in smokers: grade A for harm. In 29,133 Finnish male smokers, 20 mg of beta-carotene a day raised lung cancer by 18% and total deaths by 8% (ATBC 1994). In CARET, 18,314 people at high risk (current or former smokers, or workers exposed to asbestos) took 30 mg of beta-carotene plus 25,000 IU of vitamin A a day or placebo; the combination's lung cancer risk ratio was 1.28, the death risk ratio 1.17, and the trial stopped early (Omenn 1996). Upper limit for adults: 3,000 mcg RAE (10,000 IU) of preformed vitamin A a day, because more can cause birth defects and liver damage; take more only with blood tests or your clinician's advice (NIH ODS; check your stack). In pregnancy, don't take preformed vitamin A supplements above that limit unless your midwife or obstetric team advises it: in a study of 22,748 pregnant women, more than 10,000 IU a day from supplements went with about 4.8 times the rate of certain birth defects (Rothman 1995). Our beta-carotene page grades the beta-carotene lung cancer harm D; two large trials pointing the same way support A.

High-dose vitamin E: grade B for harm. Pooling the 11 high-dose trials (at least 400 IU daily), deaths from all causes were higher by 39 per 10,000 people, though many of those trials enrolled people with chronic disease (Miller 2005). The USPSTF recommends against beta-carotene and vitamin E supplements for preventing heart disease or cancer (USPSTF 2022 summary). See our vitamin E page.

Can a multivitamin push you over an upper limit?

Yes, when you add single-nutrient pills on top. Check your stack against these adult upper limits (NIH ODS):

Women's multivitamins often hold 18 mg of iron, while men's and seniors' formulas often hold little or none (NIH ODS).

What we'd skip

• A multivitamin to ward off heart disease or early death: no effect in large trials (Sesso 2012; Macpherson 2013).
• Beta-carotene pills if you smoke or used to: more lung cancer (Omenn 1996).
• High-dose vitamin E: more deaths in high-dose trials (Miller 2005).
• Stacking "hair, skin and nails" or immunity blends on a multivitamin without adding up vitamin A, zinc, selenium and B6 (check your stack).

Safety and interactions

• Side effects: trials of multivitamins at no more than recommended amounts found only minor ones, such as stomach upset, and no difference from placebo (Biesalski 2017); COSMOS reported no safety concerns (Sesso 2022).
• Warfarin: in 9 warfarin users with low vitamin K levels, a multivitamin with 25 mcg of vitamin K pushed blood clotting tests below the target range in all 9 (Kurnik 2004). Tell your anticoagulation clinic before starting or stopping one; see supplements and blood thinners.
• Levothyroxine and antibiotics: iron, calcium and zinc in multivitamins can bind them. A multivitamin with zinc lowered ciprofloxacin levels in 12 healthy men (Polk 1989). See can I take iron, calcium or magnesium with levothyroxine? and ask your pharmacist about spacing.
• Biotin in some multivitamins can distort lab results; tell the lab, or stop it before blood tests as your clinician advises; see does biotin affect thyroid and troponin tests?
• Iron overload: men, people past menopause and anyone with haemochromatosis (a condition that makes the body store too much iron) should choose an iron-free multivitamin unless a blood test shows they need iron (NIH ODS).
• Children and iron: keep multivitamins with iron out of reach. Between 1983 and 2000, at least 43 US children died after swallowing high-dose iron supplements (NIH ODS).

When to see a doctor

• Emergency: a child who may have swallowed adult vitamins with iron.
• Soon: tiredness, numbness or tingling in the hands and feet, a sore tongue, or memory changes, which can come with low B12, especially over 50, on metformin or on a vegan diet (NIH ODS).
• Before starting: pregnancy, kidney or liver disease, warfarin, or more than one supplement product.

Don't stop a prescribed medicine on your own; ask the prescriber or pharmacist. If you are pregnant or breastfeeding, ask your midwife or obstetric team. If you are under 18, ask a clinician.

FAQ

Do multivitamins actually work? For heart disease and living longer, no: two large trials and 21 pooled trial reports found no difference (grade A). Cancer results were mixed (grade B), and older adults in COSMOS did slightly better on memory tests (grade B).

Should healthy people take a multivitamin? The USPSTF says the evidence is insufficient to recommend one for preventing heart disease or cancer. A specific gap, such as B12 on a vegan diet or after weight-loss surgery, is a better reason.

Is a multivitamin good for adults over 50? In COSMOS, adults 60 and older scored slightly better on memory tests (grade B), but a PHS II study of men 65 and older found no memory gain, and heart and cancer outcomes did not change. Some older adults absorb B12 from food poorly, so ask about a B12 test.

What is the best time to take a multivitamin? Timing has not been tested. If your multivitamin contains iron and you take levothyroxine or certain antibiotics, ask your pharmacist about spacing.

Can I take a multivitamin with iron? Many multivitamins already contain iron, often 18 mg in women's formulas. Add the iron in every product you take; the adult upper limit is 45 mg a day.

Related pages

• Multivitamin · Vitamin B12 · Vitamin D · Vitamin E · Beta-carotene · Iron · Zinc · Folic acid
• Aging · Healthy muscle aging
• Vitamin B12 for energy · Prenatal supplements · Supplements on GLP-1 medicines · How to choose a quality supplement
• Check my stack · How we grade

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