Multivitamins are the UK's most popular supplement, but for adults who eat reasonably well the evidence that a daily multivitamin improves health, prevents disease or extends life is weak. Large, long-term trials have mostly come up empty. That does not make multivitamins dangerous, but the popular insurance policy framing promises more than the science delivers.
What a multivitamin is trying to do
A typical multivitamin contains small doses of many vitamins and minerals, aiming to cover any gaps in the diet. The logic is intuitive: if you might not get everything from food, a broad low-dose pill fills in. The problem is that intuition and trial results do not agree, at least for people who are not deficient to begin with.
In the UK, most people who eat a reasonably varied diet already meet their needs for most nutrients. The NHS advice on vitamins and minerals is that the majority of people do not need supplements at all, with a short list of specific exceptions such as vitamin D in winter and folic acid in pregnancy.
Do multivitamins actually work?
Multivitamins have been studied in some of the largest and longest nutrition trials ever run, including studies following tens of thousands of people for years. The general finding is a lack of clear benefit for the outcomes that matter most: heart disease, cancer, cognitive decline and overall mortality in well-nourished populations.
The most thorough recent review, carried out for the US Preventive Services Task Force across 84 studies and hundreds of thousands of participants, concluded there was insufficient evidence that multivitamins prevent cardiovascular disease or cancer. A large 2023 trial did report small improvements in memory scores in older adults, which drew headlines, but the effect was modest and sits against a much larger body of null results. It is not a reason for younger, well-nourished adults to start.
This is a genuinely honest area to be blunt about: a lot of people take a multivitamin every day in the belief it protects their health, and the best available evidence does not back that up for people who already eat a reasonable diet.
Why the trials keep coming up empty
Part of the explanation is that most nutrients follow a threshold pattern rather than a more-is-better one. Once you have enough of a vitamin or mineral to meet your needs, taking additional amounts does not push benefit higher; it simply raises what you excrete or, for some fat-soluble vitamins, what you store. A multivitamin adds to intake that, for most balanced eaters, is already sufficient.
There is also a well-documented pattern that people who take multivitamins tend to be healthier in general. They exercise more, smoke less and eat better, which for years made observational studies look more favourable than the controlled trials that followed. When you account for those habits, the pill itself contributes little. The Scientific Advisory Committee on Nutrition, which advises the UK government, takes a similarly cautious food-first position in its nutrient reviews.
Who might actually benefit
Targeted supplementation is different from a blanket multivitamin. Certain groups have real, evidence-based needs, usually met better by specific supplements than an all-in-one:
- Everyone in the UK for vitamin D between October and March; see our guide to vitamin D and UK guidance.
- People who are pregnant or trying to conceive, who are advised folic acid and vitamin D.
- People on vegan or largely plant-based diets, who need a reliable source of vitamin B12.
- People with a diagnosed deficiency, for example low iron; our guide to iron deficiency signs covers when to ask for a test.
- Some older adults, and people with conditions affecting appetite or absorption.
Children are a separate case with clearer guidance: the NHS recommends that children aged 6 months to 5 years take a daily supplement containing vitamins A, C and D, unless they are having more than 500ml of infant formula a day. Families who qualify for the Healthy Start scheme can get these vitamins free. That advice is specific and evidence-led, which is exactly the contrast with the adult multivitamin habit.
Appetite matters too. People eating substantially less than usual, for example during intentional weight loss with treatments that reduce appetite, can find their intake of several nutrients drops at once. Our guide to micronutrients on GLP-1 treatment covers this situation, where a standard multivitamin can be a reasonable stopgap while eating patterns settle.
When a multivitamin is reasonable anyway
There are pragmatic cases. If your diet is genuinely erratic for a period, if you are recovering from illness, or if a low-cost multivitamin gives you peace of mind and does no harm, it is a defensible choice. If you are not sure whether you need anything at all, start with our guide to whether you need supplements.
If you do buy one, keep doses sensible. Avoid megadose products, check you are not doubling up nutrients across several products, and learn what the percentages on the packaging mean; our guide to reading supplement labels explains the detail. The British Dietetic Association makes the same point in its supplements fact sheet: food first, supplements for specific, identified needs. Basic own-brand multivitamins also cost pennies a day, and expensive branded versions offer no advantage that trials can detect.
The honest bottom line
A daily multivitamin is unlikely to harm you and unlikely to do much for you if you already eat reasonably. The better move is to identify any specific gap, such as vitamin D, B12 or iron if tested low, and address that directly, rather than paying for a broad pill that trials suggest does little.
