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					  Taking dietary calcium supplements to prevent
                 colorectal cancer                                               The Cochrane review suggests
                                                                                 The efficacy of dietary calcium supplements
                                                                                 Taking a daily calcium supplement may have a small to moderate protective
Colorectal cancer                                                                effect against the growth of recurring adenomatous polyps.
Colon cancer is a type of cancer that affects men and women and is more
common in industrialised countries. The risk of colorectal cancer begins to
increase after the age of 40 years and rises sharply in the 50s.                 How it was tested
Most colorectal cancers develop from slowly growing non-cancerous                The researchers made a thorough search of the literature. They found two
(benign) polyps known as adenomatous polyps. These polyps are                    trials that randomly assigned people who had previously had polyps to
considered as risk factors for cancer in the large intestine or rectum. A        receive either a calcium supplement or a non-active treatment (placebo)
decrease in the number of polyps could potentially reduce the likelihood of      taken daily for three to four years.
developing cancer.
                                                                                 The trials involved a total of 1346 people and reported on the number of
                                                                                 people who developed at least one polyp (adenoma) during the trial.
Calcium for the prevention of colorectal cancer                                  The daily amount of calcium was 1200 mg in one trial and 2000 mg in the
                                                                                 other trial.
Calcium in the diet could potentially prevent colorectal cancer, by protecting
the membrane lining the bowel (the mucosa). Other dietary factors include
reduced fat and increased carbohydrate, high fibre and good fluid intake.
Side effects and general cautions
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The trials did not have enough people in them to take into account the
natural variations between people and to make any meaningful conclusions
about whether dietary calcium prevented colorectal cancer.
Colorectal cancer is sufficiently rare that it is extremely difficult to conduct a
controlled trial large enough and lasting long enough to identify the
protective effect of any given single nutrient or nutritional supplement, like
calcium. That is why researchers study the development of the far more
common adenomatous polyps, some of which may be pre-cancerous.

Weingarten MA, Zalmanovici A, Yaphe J. Dietary calcium supplementation
for preventing colorectal cancer and adenomatous polyps. The Cochrane
Database of Systematic Reviews 2005, Issue 2. Art. No.: CD003548.pub3.
DOI: 10.1002/14651858.CD003548.pub3.

Prepared by the Cochrane Consumer Network, supported by Australian Government funding for Cochrane Groups in Australia.

                                                                                     The Cochrane review suggests

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