Do Multivitamins Work? What the Evidence Shows

A daily multivitamin is the most popular supplement in the world. Millions of people take one as a kind of insurance, a way to cover the gaps in a busy diet and feel they have done something for their health. The pitch is simple and the pills are cheap, so the habit sticks.

The harder question is what that insurance actually buys. Multivitamins have now been tested in hundreds of thousands of people over decades, including one of the largest studies of its kind. The answer is more specific than either the marketing or the sceptics suggest. Here is what a daily multivitamin does, what it does not, and the few people who genuinely gain from one.

What a multivitamin promises

A multivitamin is a single pill that packs in a broad mix of vitamins and minerals, usually more than 20 of them, at or near the daily amount an adult needs. The logic is that a modern diet is uneven, so a daily dose fills whatever is missing and protects against shortfalls. It is a sensible idea on paper, and it is why the multivitamin became a health staple rather than a medicine.

The claims made for it, though, go much further than filling gaps. Adverts and habit have turned the multivitamin into a promise of longer life, fewer diseases and sharper thinking. Those are testable claims, and large trials and cohorts have now put them to the test. The results separate what the pill can do from what it is sold to do.

Does it help you live longer?

This is the biggest promise, and it is where the evidence is strongest. In 2024, researchers at the US National Cancer Institute pooled three large cohorts, following 390,124 generally healthy adults for up to 27 years. It is among the longest looks at multivitamin use and death ever done. The finding was blunt. Daily multivitamin users were no less likely to die than non-users over the study.

The hazard ratio for death from any cause was 1.04, where 1.00 means no difference. There was no benefit for death from cancer, heart disease or stroke either. If anything the estimate sat a fraction above 1.00, but the authors pointed to a familiar statistical trap rather than to harm from the pills. People often start a supplement when their health is already slipping, so users can look slightly worse without the vitamin being the cause. The plain reading is that a daily multivitamin did not lengthen life. As the authors put it, they "did not find evidence to support improved longevity among healthy adults who regularly take multivitamins."

Is there anything it does help?

One area has produced a real signal, and it is the brain. The COSMOS programme ran several randomised trials of a daily multivitamin against a dummy pill in older adults, then pooled three of them covering more than 5,000 people. Published in 2024, the meta-analysis found that the multivitamin group held on to memory and thinking skills slightly better over two to three years. The authors estimated the effect as the equivalent of about two years less cognitive ageing, with a clear benefit for episodic memory.

This is genuine, controlled evidence, and it is the best case in favour of a daily multivitamin. It also comes with honest limits. The effect was modest, it was measured on cognitive tests rather than on dementia diagnoses, and it was strongest in older people whose diets may already have been short on some nutrients. It is a reason for interest, not a reason to expect a multivitamin to keep anyone sharp on its own.

For disease prevention more broadly, the official verdict is caution. In 2022 the US Preventive Services Task Force reviewed the trial evidence and concluded that "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." The same review went further on two ingredients, recommending against beta-carotene and vitamin E supplements for that purpose, because the trials showed no benefit and beta-carotene raised lung cancer risk in smokers.

Who actually needs a supplement

The evidence against a longevity benefit is not an argument against all supplements. It is an argument against the scattergun multivitamin as a health tool for people who are already well fed. The NHS states plainly that "most people should get all the nutrients they need by having a varied and balanced diet." Where it advises a supplement, it is specific about the nutrient and the group, not a one-pill-covers-all approach.

Vitamin D is the clearest example. Because UK sunlight is too weak in autumn and winter for the skin to make enough vitamin D, the NHS advises that people consider a daily 10 microgram supplement over those months. Some groups need it all year, including people with darker skin, those who cover their skin or spend little time outdoors, and adults in care homes. Folic acid is advised for anyone who could become pregnant, and vitamin B12 matters for people on a fully plant-based diet. These are targeted fixes for known shortfalls, which is a different thing from a broad multivitamin.

Common mistakes

The first mistake is treating a multivitamin as a licence to eat poorly. A pill does not carry the fibre, protein and thousands of plant compounds that come with real food, and no trial has shown it can stand in for a decent diet. The second mistake is expecting it to add years. The biggest cohort found no longevity benefit, so a multivitamin is a weak lever compared with sleep, movement, not smoking and a good diet. The third mistake is assuming more is safer. Fat-soluble vitamins such as A, D and E build up in the body, and high-dose single nutrients like beta-carotene have caused harm in trials, so a sensible dose at or near the daily requirement is the safe choice.

Frequently asked questions

The bottom line

A daily multivitamin is not the longevity pill it is sold as. In the largest study to date, across nearly 400,000 adults, it did not lower the risk of early death. Its one genuine bright spot is a modest slowing of cognitive ageing in older adults, and even that is measured on tests rather than on disease. For nearly all people, a varied diet does the job, with a winter vitamin D supplement and a few targeted nutrients for those who need them. If a cheap multivitamin gives you peace of mind, it does little harm, but do not let it stand in for the food, sleep and training that genuinely improve health.

Sources

• Loftfield E, et al. Multivitamin Use and Mortality Risk in 3 Prospective US Cohorts. JAMA Network Open, 2024. pmc.ncbi.nlm.nih.gov
• Vyas CM, et al. Multivitamin-mineral supplementation and cognitive function, meta-analysis of 3 COSMOS cognitive studies. American Journal of Clinical Nutrition, 2024. pmc.ncbi.nlm.nih.gov
• US Preventive Services Task Force (Mangione CM, et al.). Vitamin, Mineral, and Multivitamin Supplementation to Prevent Cardiovascular Disease and Cancer. JAMA, 2022. jamanetwork.com
• NHS. Vitamins and minerals (overview). nhs.uk
• NHS. Vitamin D. nhs.uk