Multivitamins: is a pill a day worth it?

In many countries multivitamins are the most widely used supplement. They promise to fill the "gaps" in our diet and protect health. But what does the best evidence say?

The 2022 recommendation

In 2022 the US Preventive Services Task Force (USPSTF), an independent group of experts that reviews the evidence, published its recommendation for healthy adults. The conclusions were:

• There is not enough evidence to say whether multivitamins prevent heart disease or cancer.
• It recommends against taking beta-carotene, because in some trials it increased the risk of lung cancer in smokers.
• It recommends against vitamin E for prevention, because it showed no benefit.

The doctors' study

One of the longest trials is the Physicians' Health Study II, in which about 14,000 American doctors over 50 took an ordinary multivitamin or a placebo for on average more than 11 years. The multivitamin group had a small reduction, about 8 per cent, in cancer cases overall, but no change in heart disease or in mortality. Newer studies have suggested a small effect on memory in older people, but this still needs confirmation.

A pill cannot do what a plate of vegetables, beans and whole grains does.

When supplements make sense

This does not mean that no supplement has value. Some groups have a real need, on medical advice:

1. Women planning a pregnancy or who are pregnant: folic acid reduces the risk of some birth defects.
2. People on a vegan diet: vitamin B12 is not found naturally in plant foods.
3. Older people and people with certain conditions may lack B12, vitamin D or iron.
4. People with deficiencies proven by blood tests.

Caution

• Fat-soluble vitamins, such as A, D, E and K, build up in the body and can be harmful at high doses.
• Excess iron can be dangerous, especially for children. Keep the pills out of their reach.
• Some supplements interact with medicines. Tell your doctor what you take.

Before buying a supplement, ask yourself: what problem am I trying to solve? If the answer is "just in case", the money might be better spent on fruit, vegetables, beans and fish. If you have symptoms such as persistent tiredness or weakness, talk to your doctor and have tests before starting any treatment on your own.