Researchers may have discovered a relationship between the
risk of colorectal cancer in women and their consumption of
choline, which has until now been thought to be an essential
nutrient. The link was reported in a study published in the
Journal of the National Cancer Institute.
Choline is a nutrient found in eggs, meat (especially liver)
and dairy products. It plays an important role in the functioning
of cells and the distribution of nutrients through the body,
including a process called one-carbon metabolism. Prior studies
have shown that people with a high dietary intake of other nutrients
involved in one-carbon metabolism, such as folate, have a decreased
risk for colorectal polyps.
Colorectal polyps are often-benign tumors that develop in the
colon and can eventually lead to cancer. In the first study
to examine the issue, researchers expected to find that consumption
of choline, like folate, decreased a person's risk of developing
colorectal polyps.
To their surprise, researchers found the opposite. In a survey
of 39,246 women, researchers used food-frequency questionnaires
to estimate the choline contents of participants' diets. All
the women had no cancer or polyps when the study began, and
had at least one endoscopy between 1984 and 2002. Increased
consumption of choline was found to be correlated with a higher
risk of colorectal polyps.
"Clearly, one-carbon metabolism and its role in [cancer
development] is more complicated than originally anticipated,
and our understanding of the underlying mechanisms is probably
incomplete," wrote Regina Ziegler and Unhee Lim, of the
National Cancer Institute in Bethesda, Maryland, in an accompanying
editorial.
While a correlation does not necessarily mean that choline
is to blame for the increased colon
cancer risk, the authors speculated that it may indeed play
a role.
"Once a tumor is initiated, growth into a detectable [polyp]
depends in part on choline availability, because choline is
needed to make membranes in all rapidly growing cells,"
they wrote.
Prior studies have linked choline deficiency to fatty liver
and muscle damage.
