Supplements and cancer prevention

For cancer prevention, don't use dietary supplements.

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

What are dietary supplements?

Dietary supplements contain vitamins, minerals, herbs or plant material. They can be found in pill, capsule, tablet or liquid form and are used to supplement (add to) the diet, but they should not be considered a substitute for food.

For most people, it's sensible to get nutrients from 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.

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

Dietary supplements and cancer prevention – the evidence

Scientific research shows strong evidence that high-dose supplements of some nutrients can affect the risk of different cancers in unpredictable ways.

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.

Research shows that in general, the best wource of nourishment is food and drink and not dietary supplements. The studies examined in our Expert Report showed that while some high-does nutrient supplements can protect against cancer, others can actually raise the risk of cancer.

As these studies have been done in specific groups of people and not in the general population, there is no way of accurately predicting the risks or benefits of taking supplements. Therefore, we recommend not to use supplements to protect against cancer.

Can supplements be beneficial?

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.

If you want more advice on any of these situations, it’s best to contact your GP.

Tips for a balanced diet without dietary supplements

• Eat a variety of vegetables and fruits. Aim to eat lots of different vegetables and fruits; this way you will be making sure that you are getting all the different nutrients that you need. Try to eat five different vegetables and fruits each day.
• Eat a balance of plant foods, protein and dairy foods. Filling at least two-thirds of your plate with plant foods will help you to achieve a healthy balance.

Read all our Recommendations for Cancer Prevention