To reduce your risk of cancer, choose a balanced diet with a variety of foods rather than taking supplements.

Nutrient-rich whole foods contain substances that are necessary for good health like fibre, vitamins and minerals. Although some of these substances are available as supplements, scientists cannot be sure that we get the same benefit if we consume nutrients in this form.

Research also shows that taking high doses of some supplements could be harmful to our health.

Although some studies do show that supplements protect against some cancers, they have normally been tested in one particular group of people, so the benefits might not apply to the general population.

Some supplements can have side effects but the trials are not always able to pick them up. So for most people, it’s sensible to get nutrients from whole foods, where the balance of risks and benefits is known. By eating a balanced diet, rich in vegetables, fruits and other plant-based foods, most of us should be able to obtain all the nutrients we need.

However, some groups of people may benefit from taking supplements. These are the most common situations when taking a supplement can be beneficial:

• All women of childbearing age intending to conceive a child should take a folic acid supplement before conception and up to the 12th week of pregnancy
• Pregnant women and nursing mothers should take a vitamin D supplement and possibly an iron supplement if their iron levels are low
• Children between six months and five years could benefit from taking drops containing vitamins A, C and D, although children with a good appetite who eat a wide variety of foods may not need them
• Frail older people who have low calorie needs may benefit from a low-dose, balanced micronutrient supplement
• Older people should consider taking a vitamin D supplement, as should: people of Asian origin; people who rarely go outdoors; people who cover up all their skin when outdoors; those who don’t eat meat or oily fish
• If you want more advice on any of these situations, it’s best to contact your GP

Dietary supplements – the evidence

There is strong evidence that high-dose supplements of some nutrients can affect the risk of different cancers.

Some studies have shown that supplements can upset the balance of nutrients in the body. More research needs to be done, but this is one way that they might affect our risk of cancer.