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High-choline diet linked to colorectal polyps in women

Last Updated: 2007-08-08 17:17:01 -0400 (Reuters Health)

NEW YORK (Reuters Health) - Diets high in choline may raise a woman's risk of distal colorectal adenoma, according to findings from the Nurses' Health Study. Whether it is the choline itself that contributes to the risk, or other components of a high-choline diet, has yet to be explored, according to research results published in the Journal of the National Cancer Institute for August 15th.

The research team, led by Dr. Eunyoung Cho at Brigham and Women' Hospital in Boston, also examined the effects of choline's oxidation product betaine, and observed no significant effect on the incidence of colorectal polyps.

Because dietary choline is a methyl-group donor, as is folate, the investigators suspected it would have folate's anti-cancer characteristics.

Dr. Cho's group notes that theirs is the first epidemiologic study to evaluate the effect of dietary choline and betaine and the risk of chronic diseases, including colorectal adenoma, probably because food composition databases have only recently been available.

Their analysis included women who had provided diet information in 1984 and underwent a colonoscopy or sigmoidoscopy between 1984 and 2002 (n = 39,246). Every 2 to 4 years, the subjects completed food frequency questionnaires.

During the study period, 2408 women were diagnosed with adenoma (1841 distal colon adenomas and 675 rectal adenomas), Dr. Cho and colleagues report.

In multivariable analysis of quintiles of dietary choline, the relative risk increased from 1.00 for the lowest quintile to 1.45 for the top quintile (p < 0.001 for trend). The positive association remained statistically significant after adjusting for the amount of foods high in choline. The associated risk was strongest among those with a low folate intake and those with higher alcohol intake.

In contrast, betaine had a nonsignificant, nonlinear inverse association with colorectal adenomas (p for trend = 0.09).

Dr. Cho's group hypothesizes that "once a tumor is initiated, growth into a detectable adenoma depends in part on choline availability because choline is needed to make membranes in all rapidly growing cells."

Dr. Regina G. Ziegler and Dr. Unhee Lim write in a related editorial that "choline's role in carcinogenesis is more complicated than originally anticipated."

The editorialists, from the National Cancer Institute in Bethesda, Maryland, urge "caution in developing public health policy" until more data are available. "We should remember the surprises and complexities that emerged for beta-carotene, vitamin E, vitamin C, and selenium, other initially promising chemopreventive agents."

J Natl Cancer Inst 2007;99:1214-1215,1224-1231.

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