Calcium More Protective Against Some Polyps
High-Fiber, Low-Fat Diet Helps Calcium Prevent Colon Cancer
June 15, 2004 -- Calcium supplements could cut colon polyp risk
-- especially advanced polyps that lead to colon cancer, new research
The report appears in the latest issue of
the Journal of the National Cancer Institute.
"Our results suggest that calcium
supplementation may have a more pronounced ... effect on advanced [colon
polyps] than on other types of polyps," writes lead researcher Kristin
Wallace, MS, with Dartmouth Medical School in Lebanon, N.H.
While some research has looked at this
link, few have addressed it in any detail -- to look for the effects of calcium
on different types of colon polyps, Wallace explains. These studies make no
distinction on the effects of calcium supplements on polyp size or other
Also, what are the effects of calcium in
the diet and from pills? One study has suggested that a 700 mg supplement daily
may prevent polyps. However, it's not been clear whether a high-calcium diet
boosts or hinders that effect, she writes.
The researchers analyzed data from patients
involved in the large Calcium Polyp Prevention Study. The analysis involved 913
patients whose average age was 61 and who were followed for at least four
They had been randomly assigned to take
either 1,200 mg calcium supplements or a placebo. Each volunteer was asked
about the calcium, fat, and fiber they typically got in their diet. Each
participant had a history of having a polyp removed at least three years prior
to the start of the study. They also had a colonoscopy at the beginning of the
study to document no remaining polyps in the colon.
After four years:
The calcium group had 18% fewer noncancerous polyps and
35% fewer advanced polyps -- those with features that have a higher potential
to become colorectal cancer -- compared with the placebo group.
There was another interesting pattern:
Those with fewest polyps ate a high-calcium, high-fiber, low-fat diet. However,
the numbers did not tally up as a definitive finding, notes Wallace.
In all, her study suggests that total
calcium intake over 1,200 mg daily is necessary for colon protection -- and
that a high-fiber diet with modest levels of fat will boost the protective
effects, she writes.
Wallace's findings are in line with similar
studies but fall short of proving a preventive link between calcium, colon
polyps, and colon cancer, writes Arthur Schatzkin, PhD, with the National
Cancer Institute, in an editorial.
However, studies are in place that could
prove that this one nutritional factor -- calcium -- could offer protection
against colon cancer. "That would be a tremendous advance," writes
It's not clear how calcium acts to reduce
colon polyps, writes Wallace. It may be that calcium binds "irritants"
like bile acids and other fats in the bowel that are carcinogenic -- acting as
a sort of "soap," possibly preventing colon cancer.