Diet not vitamins 'better for preventing cancer'Evidence doesn't support supplements, says study

18 February 2008

Vitamins bottles

Look carefully at the label before you choose a supplement

People who take vitamin supplements to cut their risk of cancer may be wasting their money, a leading expert has warned.

Professor Martin Wiseman said that rather than rely on supplements people should eat a healthy diet full of fruit and vegetables.

Professor Wiseman is medical and scientific adviser for World Cancer Research Fund (WCRF).

It published a report at the end of last year examining more than 7,000 studies about how lifestyle affects cancer risk.

Supplement results

This included evidence from almost 50 different clinical trials on supplements, with experts behind the study finding the results too inconsistent to recommend using them.

Professor Wiseman said: ‘Many people still think they can reduce their cancer risk by taking supplements, but the evidence does not support this.

‘This is why we need to get across the message that supplements should not be taken for cancer prevention and instead people should be aiming to get the nutrients they need from their diet alone.

People should aim to get the nutrients they need from their diet alone

Professor WisemanScientific advisor, WCRF

‘It is true that there is some evidence that certain supplements may protect against cancer, but we simply do not know enough to be able to confidently predict the balance of risks and benefits for the general population.'

'Protective effect'

Pamela Mason, spokeswoman for the Health Supplements Information Service (HSIS), said some studies had shown a protective effect against cancer in some people taking supplements.

But she said far more studies were needed into the effects of vitamins.

According to the WCRF report the following supplements had some evidence of leading to a decreased cancer risk:

  • calcium decreases bowel cancer risk (probable evidence). However, other evidence in the report found that calcium probably increases risk of prostate cancer
  • selenium decreases prostate cancer risk (probable evidence)
  • retinol decreases skin cancer risk (limited suggestive evidence)
  • alpha-tocopherol decreases prostate cancer risk (limited suggestive evidence)
  • selenium decreases bowel and lung cancer risk (limited suggestive evidence)

But the WCRF report found the following supplements had some evidence of leading to an increased cancer risk:

  • beta carotene increases risk of lung cancer in smokers (convincing evidence)
  • selenium increases skin cancer risk (limited suggestive evidence)
  • retinol increases lung cancer risk in smokers (limited suggestive evidence).