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Vitamin supplements of no benefit for colorectal cancer risk: Study

15-Oct-2012
Last updated on 15-Oct-2012 at 17:22 GMT

Vitamin supplements no benefit for colorectal cacncer risk

Combined supplementation with folic acid, vitamin B6 and vitamin B12 has no statistically significant effect on the risk of colorectal adenoma, according to new research.

The study – published in the Journal of the National Cancer Institute – analyses data from more than 5,000 women who took part in a randomised, double-blind, placebo-controlled trial of female health professionals at high risk for cardiovascular disease.

The researchers, led by Dr Yiqing Song of Harvard Medical School, USA, reveal that although previous research has suggested such supplements could help to battle the risk of such cancers, but the new data found the risk of colorectal adenoma – a precursor to colorectal cancer –was not significantly affected.
“Our findings do not support recommending B-vitamin supplementation for the prevention of colorectal adenomas,” wrote the researchers – adding that more evidence is needed in order to verify their findings.

In an accompanying editorial, Dr Regina Ziegler, noted that while the comparison of folate intake from the highest to lowest groups showed no statistically significant reduction in adenoma risk, further study is needed. 

“These observational epidemiology results, from prospective studies of diet and supplements or of circulating biomarkers, are provocative and imply that the role of folate and other B vitamins in colorectal carcinogenesis merits continued exploration,” she said.

Early promise

Song and his colleagues revealed that previous in vitro and animal studies have shown B vitamins are able to combat colorectal carcinogenesis, whilst some observational epidemiologic studies have suggested high folate intake could help to reduce the risk of colon cancer by between 20% and 40%.

Randomised trial

In order to determine the potential effects of folic acid, B6 and vitamin B12 on the risk of colorectal adenoma the researchers analysed data from the Women’s Antioxidant and Folic Acid Cardiovascular Study (WAFACS) – a randomised, double-blind, placebo-controlled trial involving 5,442 females.

Participants were randomly assigned to a combination of folic acid, vitamin B6 and vitamin B12, or placebo.  This analysis included 1,470 WAFACS participants who received a follow-up endoscopy at some point during the 9 year follow-up. 

Song and his team found that the risk of colorectal adenoma among women receiving the supplement was not statistically significantly different to those receiving placebo.
“The risk of colorectal adenoma was similar among participants receiving treatment (24.3%, 180 of 741 participants) vs placebo (24.0%, 175 of 729 participants),” they wrote.
They also found that consumption of alcohol – known to be a folate ‘antagonist’ did not influence the effect of supplements on colorectal adenoma risk.

Source: Journal of the National Cancer Institute
Published online ahead of print, doi:10.1093/jnci/djs370
Effect of combined Folic Acid, Vitamin B6, and Vitamin B12 on colorectal Adenoma
Authors: Yiqing Song, JoAnn E. Manson, I-Min Lee, Nancy R. Cook, Ligi Paul, et al

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