The Bottom Line Up Front
For most healthy adults eating a reasonably varied diet, a daily multivitamin is unlikely to prevent major diseases or extend your life. But specific populations, including pregnant women, older adults, people with restricted diets, and those with documented deficiencies, can benefit meaningfully. The honest answer is: it depends entirely on who you are and what you eat.
The Big Studies: What We Actually Know
The COSMOS Trial (2022-2024)
The COcoa Supplement and Multivitamin Outcomes Study (COSMOS) is the most important recent evidence. This was a large, rigorous, randomized, double-blind, placebo-controlled trial involving over 21,000 adults aged 60 and older, run by researchers at Brigham and Women's Hospital and Harvard.
The headline results for the multivitamin arm (using Centrum Silver):
- Cancer: No statistically significant reduction in total cancer incidence
- Cardiovascular disease: No significant reduction in major cardiovascular events
- Cognition: The COSMOS-Mind sub-study found a modest but statistically significant benefit for global cognition, roughly equivalent to slowing cognitive aging by about 2 years. This was the most encouraging finding, though researchers noted it needs replication
- Mortality: No significant effect on overall mortality
COSMOS followed up on the earlier Physicians' Health Study II (PHS II), which tracked over 14,000 male physicians for more than a decade. PHS II found a modest 8% reduction in total cancer risk with daily multivitamin use, but no effect on cardiovascular disease or mortality.
The U.S. Preventive Services Task Force (USPSTF)
In 2022, the USPSTF updated its recommendation on vitamin supplementation for disease prevention. Their conclusion: "The current evidence is insufficient to assess the balance of benefits and harms of the use of multivitamin supplements for the prevention of cardiovascular disease or cancer." This was categorized as an "I" statement, meaning they could not determine whether the benefits outweigh the harms, not that there is no benefit.
Notably, they recommended against beta-carotene supplementation (which increases lung cancer risk in smokers) and found insufficient evidence for vitamin E supplementation.
Earlier Large-Scale Trials
Several earlier studies also inform the picture:
- The Women's Health Initiative found no significant effect of multivitamins on cancer, heart disease, or mortality in postmenopausal women
- The Iowa Women's Health Study found a possible small increase in mortality associated with certain supplements (though this was observational and heavily debated)
- Multiple meta-analyses have found no consistent evidence that multivitamins reduce mortality in general adult populations
So Who Actually Benefits?
The population-level studies above test whether everyone should take a multivitamin. The answer to that question is probably no. But the question "should YOU take a multivitamin" depends on your specific situation.
Strong evidence for supplementation
Pregnant women and women trying to conceive: Folate (folic acid or methylfolate) supplementation before and during early pregnancy significantly reduces the risk of neural tube defects. This is one of the most well-established findings in all of nutrition science. Prenatal vitamins also provide iron, DHA, and other nutrients that have meaningful evidence during pregnancy. This is the single clearest case for a multivitamin.
Adults over 65: Older adults have increased risk of deficiency in vitamin B12 (due to reduced absorption), vitamin D (due to less skin synthesis), and calcium. The COSMOS cognitive benefit was found in this age group. A multivitamin as nutritional insurance is reasonable for this population, even if the disease-prevention evidence is modest.
People with documented deficiencies: If blood work shows you are low in specific nutrients, supplementation is clearly warranted. Common deficiencies include vitamin D (especially at higher latitudes), iron (especially in menstruating women and vegetarians), B12 (especially in vegans), and magnesium.
Reasonable case for supplementation
Vegans and strict vegetarians: Vitamin B12 is essentially absent from plant foods. Vegans need to supplement B12, and may also benefit from supplemental iron, zinc, iodine, and omega-3 (DHA/EPA). A well-chosen multivitamin can serve as a convenient vehicle for several of these.
People with highly restricted diets: If you eat fewer than 1,500 calories per day, eliminate entire food groups, or have a medical condition that impairs absorption (celiac disease, IBD, post-bariatric surgery), a multivitamin provides a reasonable safety net.
Heavy exercisers and athletes: Increased metabolic demands, sweating, and caloric turnover can increase requirements for certain nutrients, particularly magnesium, zinc, and B vitamins.
Probably does not need a multivitamin
Healthy adults eating a varied diet: If you eat a mix of vegetables, fruits, whole grains, lean proteins, and dairy (or fortified alternatives), you are likely getting adequate levels of most nutrients. The large-scale trials consistently fail to show meaningful benefits in this population. Your money would be better spent on food quality.
Multivitamin vs. Targeted Supplementation
One underappreciated argument against multivitamins: they are a blunt instrument. Most multivitamins include 20-30 ingredients, many of which you almost certainly get enough of from food (biotin, for example, is virtually impossible to be deficient in from a normal diet). Meanwhile, the nutrients you are most likely to be deficient in (vitamin D, magnesium, omega-3) are often included at doses well below the clinically effective range.
Consider this example: a typical multivitamin contains 400-800 IU of vitamin D. But the clinically effective dose for most people who are insufficient is 2,000-4,000 IU per day. It contains 50-100 mg of magnesium, when the effective supplement dose is 200-400 mg. It contains no omega-3 at all, or a token 100 mg when the effective dose is 1,000-2,000 mg of EPA+DHA.
In many cases, a smarter and more cost-effective approach is to get a blood test, identify any actual deficiencies, and supplement those nutrients at clinically effective doses. You might end up with a vitamin D supplement, a magnesium supplement, and a fish oil, and skip the multivitamin entirely.
If You Do Take a Multi: What to Look For
Not all multivitamins are created equal. Here are the key things our multivitamin scorecard evaluates:
- Active forms of vitamins: Methylfolate (not folic acid), methylcobalamin (not cyanocobalamin), vitamin D3 (not D2), vitamin K2 as MK-7 (if included). Active forms are better absorbed and more effective for many people
- No mega-doses: More is not better. Some multivitamins include 1,000-5,000% of the daily value for certain nutrients, which is unnecessary and in some cases risky (excess vitamin A, for example, can cause liver damage)
- Meaningful doses of commonly deficient nutrients: At minimum, look for 1,000-2,000 IU of vitamin D3, 200+ mg of magnesium, and 15 mg of zinc
- Third-party testing: The multivitamin category has some of the worst quality control issues in the supplement industry. A ConsumerLab review found that nearly half of multivitamins tested did not pass quality checks, primarily due to having too much or too little of listed ingredients
- No proprietary blends: You should be able to see exactly how much of each ingredient you are getting
The Cost Equation
Premium multivitamins from brands like Thorne, Pure Encapsulations, and Ritual cost $1.00-$2.00 per day. Budget options from Nature Made, Kirkland, and Centrum cost $0.05-$0.15 per day. The premium brands typically use better ingredient forms and have stronger third-party testing.
But here is the value question: if you are spending $1.50/day on a premium multi that includes sub-clinical doses of nutrients you are not deficient in, would that money be better spent on $0.30/day of targeted supplements addressing actual gaps? In most cases, yes.
Check our multivitamin scorecard for detailed cost-per-day comparisons and quality assessments across the top-selling products.
Our Take
The multivitamin is neither the miracle that supplement companies sell nor the waste of money that some critics claim. The truth is nuanced and depends on your individual situation. If you are pregnant, over 65, eat a restricted diet, or have known deficiencies, a well-chosen multivitamin is a reasonable choice. For most healthy adults eating a varied diet, targeted supplementation based on blood work is likely a better use of your money.
Whatever you decide, check our scoring methodology to understand how we evaluate products, and remember that the most important "supplement" for health is a varied, nutrient-dense diet.