Is it worth taking supplements – and can they prevent cancer?

Vitamin pills and supplements

Should we take vitamins or are we doing more harm than good? Health expert Matt Lambert looks at the evidence for adding pills to your diet and whether supplements affect your risk of cancer.

The supplement industry is big business – the UK market was estimated at a whopping £520 million in 2022. Nearly half of us say we use them regularly, taking tablets such as vitamin D, vitamin C, iron, fish oil and probiotics, and the most widely used are multivitamins.

But why are health supplements so popular? Leaving clever marketing to one side, people use them to ensure they are not missing out on any vitamins and minerals from their diet. Probably the main reason people take supplements is the belief that they will improve their health in some way – or prevent specific diseases.

Vitamins and minerals are fundamental in helping to keep our bodies functioning properly, but taking more than we need isn’t the key to long-lasting health. The findings from a large scientific review – which included more than 287,000 people – did not support the intake of supplements to prevent chronic disease. In fact, research has shown that nutrients obtained from food, not supplements, are associated with a lower risk of cancer.

One of World Cancer Research Fund’s Cancer Prevention Recommendations is don’t use supplements for cancer prevention, as there is strong evidence that some high-dose supplements can be harmful – such as high-dose beta-carotene supplements, which can increase the risk of lung cancer in smokers and non-smokers. As the effect of supplements on cancer risk is unclear, it’s best not to use them to protect yourself against cancer.

Instead, meet your nutritional needs by eating a healthy, balanced diet – food provides a lot more than just vitamins and minerals, such as fibre and other special plant chemicals like phytonutrients – something that supplements can’t provide. Vitamins and minerals are also often absorbed more efficiently by the body in food form.

Who should take supplements?

While most people can get all the nutrients their body needs by eating a healthy, balanced diet, there are times when supplements are recommended:

A pregnant woman drinking

  • The UK government recommends that everyone should consider taking a daily supplement containing 10 micrograms of vitamin D during autumn and winter. If you have dark skin or are not exposed to much sun (for example, if you’re housebound or choose to cover your skin), you are more likely to have lower vitamin D levels. In this situation, you may want to consider taking a 10-microgram vitamin D supplement throughout the year.
  • Women who are trying for a baby or are in the first 12 weeks of their pregnancy should take a folic acid supplement.
  • Older people with a poor appetite may benefit from certain supplements.
  • Vegans may be at risk of certain deficiencies such as vitamin B12, which is mainly found in meat, eggs, and dairy products. Check our our advice for people going vegan.
  • People with bowel disease may not be able to absorb enough nutrients from their diet or to eat a normal diet.
  • People living with and beyond cancer may have a limited diet due to the effects of cancer and its treatment. Speak to your doctor if you are concerned – we have more information for people living with cancer here.

If you have been advised to take a supplement by a health professional, check the label to see how much of the Reference Intake (RI) it contains – it’s advisable to check that it contains 100% of the RI – and no higher. Some supplements contain as much as 1,000% of the RI!

And remember, you can’t make up for a poor diet by taking certain supplements – no supplement can ever have the same benefits as eating a healthy diet. If you feel you could be lacking in certain vitamins and minerals, it is best to look at changing your diet first, rather than going for certain supplements. To help you get the nutrients your body needs and to reduce your risk of cancer, aim to:

Note: you should only add certain supplements to your diet on the advice of a health professional.

Matt Lambert is Health Information and Promotion Manager at World Cancer Research Fund. Read all his blogs here and follow him on Twitter.