Daily vitamins have no role in cancer prevention

TAKING folic acid, vitamin B₆ or B₁₂ supplements has no effect on the incidence of cancer in women, new research shows, contradicting previous studies that had indicated they may be preventive.

A US randomised trial has found the widely used supplements, while not harmful, do not prevent incidence of total invasive cancer or breast cancer. Observational studies had indicated they may prevent colorectal cancer and breast cancer in particular.   

More than 5000 women aged 42 or older received a daily combination of 2.5 mg folic acid, 50 mg vitamin B₆ and 1 mg vitamin B₁₂, or placebo. After 7.3 years, the two groups had a similar risk of developing all cancer, breast cancer or of death from cancer.   

Professor Ian Olver, CEO of the Cancer Council Australia, said the results invalidated the use of folate supplements or multivitamins to prevent cancer.

“This large study has shown that taking daily vitamins, if you are taking them because you thought it would help prevent cancer, then it hasn’t shown evidence of that,” Professor Olver said.

“The data had been somewhat equivocal in the past, and some smaller, observational studies suggested there may be an effect.” 

However, Professor Olver said it was equally comforting to know that folate supplementation did not seem to promote tumour development, as had been suspected by some experts.

“There was a suggestion that if folate stopped the initiation of cancer, it could do the opposite with established cancer.This study offers absolutely no credence for that theory at all. It’s not going to promote cancer so you can safely give folate supplements.”

Mandatory folate fortification of bread is to commence in Australia in September 2009 to prevent neural tube defects.

JAMA 2008; 300:2012-21.