Vitamin and mineral supplements are widely used, but scientific evidence does not support a simple conclusion that everyone needs them — or that taking more necessarily produces better health.

Instead, research points to a more specific conclusion: certain vitamins and minerals can provide important benefits for particular people, nutritional deficiencies, life stages and medical circumstances. For generally well-nourished people, however, evidence supporting routine supplementation for broad disease prevention is considerably more limited.

For this article, AABEAT.TV reviewed information from government and scientific authorities including the U.S. National Institutes of Health (NIH), Centers for Disease Control and Prevention (CDC), Health Canada, European Food Safety Authority (EFSA) and peer-reviewed randomized clinical research. Here is what those sources actually tell us.

1. Multivitamins can help meet nutritional needs — but they don't replace food

The NIH Office of Dietary Supplements says that a person's nutritional needs should generally be met primarily through food, including fortified foods. However, NIH also recognizes that dietary supplements may be useful when specific nutrient requirements cannot be met through food alone, particularly during certain life stages.

Importantly, NIH's review of the evidence says multivitamin/mineral supplements have not reliably reduced the risk of chronic diseases in clinical trials and observational research. An evidence review cited by NIH found little or no benefit in preventing cardiovascular disease, cancer or death overall, although some individual outcomes and populations remain subjects of ongoing research.

Source: U.S. National Institutes of Health — Office of Dietary Supplements, Multivitamin/mineral Supplements: Fact Sheet for Health Professionals; NIH Vitamin & Mineral Supplement Fact Sheets.

2. Folic acid: one of the clearest evidence-based uses

Folic acid provides one of the strongest examples of supplementation being recommended for a specific public-health purpose. The U.S. Centers for Disease Control and Prevention recommends that women capable of becoming pregnant obtain 400 micrograms (mcg) of folic acid every day. According to the CDC, getting 400 mcg of folic acid daily can help prevent serious birth defects of the brain and spine known as neural-tube defects (NTDs). The CDC also notes that folic acid is the form of folate shown in studies to help prevent NTDs.

Source: U.S. Centers for Disease Control and Prevention, About Folic Acid; Folic Acid: Sources and Recommended Intake.

Canada provides similar guidance. Health Canada's current dietary guidance advises adults and adolescents who could become pregnant to take a daily multivitamin containing 400 mcg (0.4 mg) of folic acid to decrease the risk of a pregnancy affected by neural-tube defects.

Source: Government of Canada / Health Canada, Applying Canada's Dietary Guidelines: Advice on Vitamin and Mineral Supplementation.

This is an important example of how supplement evidence should be interpreted: a particular nutrient has an established benefit for a particular population and purpose. That does not mean everyone needs the same supplement.

3. Multivitamins and cognitive aging: promising evidence in older adults

One of the more interesting recent findings comes from the COcoa Supplement and Multivitamin Outcomes Study (COSMOS). A 2024 randomized clinical trial and meta-analysis examined three COSMOS cognitive studies involving older U.S. adults. Researchers reported statistically significant benefits from daily multivitamin/mineral supplementation for global cognition and episodic memory. The researchers estimated that the magnitude of the effect on global cognition was approximately equivalent to reducing cognitive aging by two years.

But this finding requires an important qualification. The study does not establish that multivitamins prevent Alzheimer's disease or dementia, nor does it prove that every person taking a multivitamin will experience a cognitive benefit. It is evidence of a measured cognitive effect in the population studied.

Peer-reviewed research: Vyas CM, Manson JE, Sesso HD, et al. "Effect of multivitamin-mineral supplementation versus placebo on cognitive function: results from the clinic subcohort of COSMOS and meta-analysis of 3 cognitive studies within COSMOS." American Journal of Clinical Nutrition. 2024;119(3):692–701. PMID: 38244989. DOI: 10.1016/j.ajcnut.2023.12.011. PubMed | Full-text research archive.

4. Vitamin D: essential nutrient, but disease-prevention claims need context

Vitamin D is essential to human health, but research on supplementation illustrates why broad claims about vitamins can become misleading. Vitamin D has established physiological roles, including supporting calcium absorption and bone health. But researchers have also investigated whether additional vitamin-D supplementation can prevent major chronic diseases.

One of the largest studies was the U.S. VITamin D and OmegA-3 TriaL (VITAL). The randomized, placebo-controlled trial included 25,871 U.S. adults and examined vitamin D3 supplementation at 2,000 IU per day. The primary finding was important: vitamin-D supplementation did not result in a significantly lower incidence of invasive cancer or major cardiovascular events compared with placebo during the trial.

That does not mean vitamin D is unimportant. It means evidence supporting vitamin D for maintaining adequate nutritional status should not automatically be transformed into claims that supplementation prevents cancer, heart attacks or other diseases.

Peer-reviewed research: Manson JE, Cook NR, Lee IM, et al. "Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease." New England Journal of Medicine. 2019;380:33–44. PMID: 30415629. DOI: 10.1056/NEJMoa1809944. PubMed.

5. Vitamin B12: deficiency changes the question

Vitamin B12 illustrates another fundamental principle: the value of supplementation can depend heavily on whether a person actually needs the nutrient. Vitamin B12 is required for important biological functions, including healthy blood and neurological function. Deficiency can have significant consequences, and certain people — including some older adults and people with conditions affecting nutrient absorption — can have difficulty obtaining or absorbing adequate B12.

For someone with an established deficiency, supplementation may therefore have an entirely different risk-benefit profile than it does for someone whose B12 status is already adequate. Consumers can review NIH's evidence-based information concerning B12, including recommended amounts, food sources, deficiency and supplementation.

Source: NIH Office of Dietary Supplements, Vitamin & Mineral Fact Sheet Directory.

6. What about vitamin C and the common cold?

Vitamin C provides a useful lesson in interpreting supplement research. It is frequently marketed or discussed in connection with colds and immune health. However, a scientific finding involving the duration or severity of symptoms is not equivalent to demonstrating that a supplement prevents or cures an infection. That distinction matters. Consumers should look at the actual outcome measured in a study rather than assuming that research involving an immune-related outcome establishes general "immune boosting" or disease-prevention effects.

Source: NIH Office of Dietary Supplements, Vitamin & Mineral Fact Sheet Directory.

7. Europe: how much of a nutrient do healthy people actually need?

The European Food Safety Authority (EFSA) uses Dietary Reference Values, or DRVs, to describe nutrient requirements. EFSA explains that nutrient requirements can vary according to factors including age, sex, physical activity, pregnancy, dietary habits and genetic background. This is another reason a single supplement recommendation cannot automatically be applied to everyone.

EFSA's framework includes measures such as:

  • Average Requirement
  • Population Reference Intake
  • Adequate Intake
  • Reference Intake ranges

These values help health professionals determine amounts of nutrients needed to maintain health in otherwise healthy people and populations.

Source: European Food Safety Authority, Dietary Reference Values.

What the evidence does — and does not — show

When the evidence is considered together, several important distinctions emerge. Evidence supports certain targeted uses: examples include folic-acid supplementation for people capable of becoming pregnant and treatment or prevention of particular nutrient deficiencies. Recent randomized research has also produced promising findings concerning multivitamin supplementation and cognition among older adults.

But evidence from one population cannot automatically be generalized. A benefit demonstrated among deficient people does not prove the same benefit among people with adequate nutritional status. A study involving adults over 60 does not establish the same outcome among adults in their 20s or 30s. A specific formulation tested in a randomized trial does not establish that every supplement containing similar ingredients produces the same outcome. And evidence that a nutrient is necessary for normal biological function does not automatically establish that taking additional amounts improves that function beyond normal levels.

More isn't necessarily better

Vitamins and minerals are biologically active substances. That means taking increasingly large amounts isn't automatically beneficial. Some nutrients can cause adverse effects at excessive doses, and supplements can interact with medications. For example, the NIH notes that vitamin K can interact with anticoagulant medications such as warfarin. This is one reason consumers should be cautious about assembling high-dose supplement regimens based on isolated studies or social-media recommendations.

Source: NIH Office of Dietary Supplements, Multivitamin/mineral Supplements — Health Professional Fact Sheet.

So, do vitamin supplements really work?

The research suggests that the original question is too broad. A more scientifically useful question is: which nutrient, for which person, for what purpose, at what dose — and supported by what evidence?

For certain populations and circumstances, supplementation can provide important and well-established benefits. For other uses, evidence remains preliminary, mixed or does not demonstrate the claimed benefit.

The most defensible conclusion from the evidence reviewed by AABEAT.TV is this: vitamin and mineral supplements can be beneficial when they address a specific nutritional need, deficiency, life stage or evidence-supported circumstance. Current evidence does not establish that everyone benefits from routine or high-dose supplementation, and results from one population or condition should not automatically be generalized to others.

Sources & research

U.S. government sources
National Institutes of Health — Office of Dietary Supplements, Multivitamin/mineral Supplements — Health Professional Fact Sheet
NIH Office of Dietary Supplements, Vitamin & Mineral Supplement Fact Sheets
Centers for Disease Control and Prevention, About Folic Acid
CDC, Folic Acid: Sources and Recommended Intake

Canadian government source
Health Canada / Government of Canada, Applying Canada's Dietary Guidelines: Advice on Vitamin and Mineral Supplementation

European scientific authority
European Food Safety Authority (EFSA), Dietary Reference Values

Peer-reviewed clinical research
Vyas CM, Manson JE, Sesso HD, et al. (2024). Effect of multivitamin-mineral supplementation versus placebo on cognitive function: results from COSMOS and meta-analysis of three cognitive studies. American Journal of Clinical Nutrition. 119(3):692–701. PMID: 38244989. pubmed.ncbi.nlm.nih.gov
Manson JE, Cook NR, Lee IM, et al. (2019). Vitamin D Supplements and Prevention of Cancer and Cardiovascular Disease. New England Journal of Medicine. 380:33–44. PMID: 30415629. pubmed.ncbi.nlm.nih.gov

AABEAT.TV Editorial & Medical Disclaimer: This article is provided for general educational and informational purposes only. It is not medical advice and is not intended to diagnose, treat, cure or prevent any disease. AABEAT.TV does not recommend or endorse any specific vitamin, dietary supplement, product, manufacturer, brand or dosage through this article. Descriptions of research findings are limited to the populations, interventions and outcomes studied and should not be interpreted as guarantees of individual results. Scientific evidence and public-health guidance can change as new evidence becomes available. Dietary supplements can interact with medications and may not be appropriate for everyone. Readers should consult an appropriately qualified healthcare professional regarding individual nutritional needs, medical conditions, medications and supplement use. References to NIH, CDC, FDA, Health Canada, EFSA or other governmental, academic or scientific organizations are provided solely as sources of information and do not imply endorsement of AABEAT.TV by those organizations.

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