Is there any scientific evidence that multivitamins work?

December 27, 2025 •

5 min read

Despite the widespread popularity of multivitamins, with over a third of American adults using them, decades of large-scale scientific studies have consistently shown little to no health benefit for the average person. Is there any scientific evidence that multivitamins work, or is it mostly marketing hype? This article explores the research to provide a clear, evidence-based answer.

Quick Summary

Decades of research indicate that, for most healthy individuals, multivitamins offer no significant health benefits for preventing chronic diseases like cancer and heart disease. While they can help fill nutritional gaps for some specific populations with deficiencies, evidence suggests healthy people are better served by a balanced diet.

Key Points

General Health Benefits: For most healthy people, large-scale studies show no significant benefit from multivitamins in preventing heart disease, cancer, or cognitive decline.
Specific Populations May Benefit: Targeted groups like pregnant women, older adults, vegans, and those with malabsorption issues can benefit from supplementation to fill specific nutritional gaps.
No Replacement for Diet: Multivitamins cannot replicate the complex array of nutrients, fiber, and other beneficial compounds found in whole foods.
Evidence is Mixed on Specific Outcomes: Some recent studies suggest a modest benefit for memory in older adults, while evidence for cancer and cardiovascular prevention is largely unsupportive.
Potential for Harm: Excessive intake of fat-soluble vitamins (A, D, E, K) from multivitamins and fortified foods can be harmful, and high doses of beta-carotene are linked to increased lung cancer risk in smokers.
Marketing vs. Regulation: The dietary supplement industry is not strictly regulated by agencies like the FDA, allowing for broad marketing claims that are not backed by rigorous science.

The Scientific Consensus on Multivitamins

For years, multivitamins have been a staple in medicine cabinets, sold on the promise of nutritional insurance and disease prevention. However, the scientific evidence from numerous large-scale, randomized controlled trials (RCTs), considered the gold standard of medical research, offers a sobering perspective for the general, healthy population. Multiple extensive reviews and meta-analyses have found no overall benefit for the prevention of chronic diseases like cardiovascular disease, cancer, or age-related cognitive decline in healthy adults.

A 2024 analysis published in JAMA Network Open, which looked at data from nearly 400,000 healthy US adults over two decades, concluded that regular multivitamin use was not associated with a lower risk of death from any cause. In fact, some studies have even pointed toward potential harm associated with certain vitamins, particularly in specific at-risk populations.

Limitations of Scientific Evidence

Interpreting the scientific literature on multivitamins is complex for several reasons:

Methodological Challenges: Many early studies were observational, comparing people who chose to take supplements to those who did not. Since supplement users often have healthier lifestyles to begin with, attributing health benefits solely to the multivitamin is difficult. Randomized controlled trials, while more robust, must be very long-term to observe effects on chronic diseases, and different trials often use varying multivitamin formulations.
Dietary Context: The effectiveness of multivitamins depends heavily on an individual's diet. For people with sufficient nutrient intake from food alone, taking a multivitamin provides no additional benefit and may lead to excessive intake of certain fat-soluble vitamins (A, D, E, K). In populations with known micronutrient deficiencies, however, supplements can be vital.
Marketing vs. Science: Aggressive marketing often overstates the benefits of multivitamins. Because dietary supplements are less strictly regulated by agencies like the FDA than prescription drugs, companies can make broad, unsubstantiated claims about promoting overall health. The legally required disclaimer, stating that statements have not been evaluated by the FDA and the product is not intended to treat or prevent disease, is often overlooked by consumers.

Scientific Findings Across Different Health Outcomes

Evidence regarding multivitamins' impact on specific health conditions is mixed and often lacks strong support for general use.

Cardiovascular Health: The Physicians' Health Study II, a large-scale RCT following male physicians for over a decade, found no protective effect of multivitamins against heart attacks, strokes, or cardiovascular mortality. A 2018 meta-analysis also concluded no benefit for overall cardiovascular outcomes.
Cancer: The Physicians' Health Study II showed a modest 8% reduction in total cancer risk in men, but no reduction in overall cancer mortality. Other studies have shown mixed results, with some linking specific vitamins (like beta-carotene in smokers) to increased cancer risk.
Cognitive Function: Recent ancillary studies to the COcoa Supplement and Multivitamin Outcomes Study (COSMOS) have shown promising results. In older adults, daily multivitamin use was found to modestly improve cognitive function, memory, and slow cognitive aging over a few years. However, older studies often found no protective effect.
Bone Health: Studies on vitamin D and calcium supplementation for bone health, often included in multivitamins, have shown mixed results. Some trials have failed to show a benefit in preventing fractures, while targeted supplementation is still recommended for at-risk individuals.
Immune Function: While some studies show multivitamins can improve micronutrient status in older or specific deficient populations, evidence for a significant reduction in general illness is not definitive. A balanced diet provides a more complete range of immune-supporting nutrients and compounds.

Comparison of Nutrient Sources: Food vs. Supplements


Feature	Nutrient-Dense Whole Foods	Multivitamin Supplements
Nutrient Complexity	Contain a wide array of vitamins, minerals, antioxidants, and fiber in a natural matrix.	Provide isolated, standardized doses of specific vitamins and minerals.
Bioavailability	Nutrients are often more readily absorbed and utilized by the body due to synergistic compounds.	Absorption can vary based on the specific formulation and individual factors.
Health Benefits	Supported by overwhelming evidence to prevent chronic disease and promote long-term health.	No evidence for overall chronic disease prevention in healthy individuals.
Synergy	The combination of nutrients in food works synergistically to enhance health outcomes.	May lack synergistic benefits and can sometimes interfere with the absorption of other minerals.
Regulation	Regulated as food, with safety and nutritional standards.	Regulated as a food product, with less stringent requirements for proving efficacy or safety.

Specific Populations That May Benefit

While the evidence does not support multivitamins for most healthy adults, certain groups may have specific nutritional needs that justify supplementation under a doctor's supervision:

Pregnant and breastfeeding women: Require higher amounts of specific nutrients like folate, iron, and iodine.
Older adults: May have difficulty absorbing vitamin B12 and require more vitamin D and calcium.
Vegans and vegetarians: Can be at risk for vitamin B12 deficiency, as it is found primarily in animal products. They may also need to supplement for other nutrients like iron, zinc, and vitamin D.
Individuals with Malabsorption Issues: People with certain medical conditions like Crohn's disease or who have had bariatric surgery may have impaired nutrient absorption.
Individuals with a Low-Calorie or Restrictive Diet: Those on diets that exclude entire food groups or are very low in calories may struggle to meet daily nutrient requirements.

Outbound Link

For a detailed, evidence-based summary of multivitamin research for health professionals, the National Institutes of Health provides comprehensive fact sheets. National Institutes of Health Fact Sheets

Conclusion

For the average, healthy adult, the scientific evidence does not support the use of multivitamins as a shortcut to better health or as a preventative measure against major chronic diseases. Decades of large-scale randomized trials have consistently shown no significant health benefits in these areas. While multivitamins may serve a role in addressing specific nutrient deficiencies in targeted populations like pregnant women, older adults, or those with restricted diets, they are not a substitute for a healthy diet rich in whole foods. Relying on a balanced diet of fruits, vegetables, whole grains, and lean proteins remains the most effective and scientifically supported approach to obtaining the full spectrum of nutrients and promoting long-term well-being. Consult with a healthcare provider or registered dietitian to determine if supplementation is right for you, and remember that whole foods provide complex nutritional benefits that a pill cannot replicate.

Frequently Asked Questions

For most healthy individuals who eat a balanced diet, it is likely pointless to take a multivitamin for overall disease prevention. The body is very good at absorbing necessary nutrients from a well-rounded diet. While generally safe, the cost may not offer any discernible health benefits.

No, a multivitamin cannot replace a healthy diet. Whole foods provide a complex array of nutrients, antioxidants, fiber, and phytochemicals that work synergistically for health. A pill only provides isolated vitamins and minerals and lacks this crucial synergy.

No, scientific evidence from large randomized controlled trials, including the Physicians' Health Study II, has found no protective effect of multivitamins against heart attacks, strokes, or other cardiovascular events in healthy adults.

The evidence is mixed, and definitive conclusions cannot be made for the general population. Some studies have shown a modest reduction in cancer risk in specific male populations, while others have shown no effect or even increased risk, particularly in smokers taking beta-carotene.

Some recent studies, including ancillary trials to the COSMOS study, have found that daily multivitamin use can modestly improve cognitive function and memory in older adults. However, older research often showed no such benefits, so more research is needed.

Yes, risks can include excessive intake of certain nutrients, especially fat-soluble vitamins (A, D, E, K), which can build up to toxic levels. Specific risks include increased lung cancer risk for smokers taking high-dose beta-carotene and potential medication interactions.

It is advisable to consult a healthcare provider if you are pregnant, an older adult, follow a restrictive diet like veganism, have a diagnosed nutrient deficiency, or have a medical condition affecting absorption. They can determine if supplementation is appropriate for your specific needs.