Milk, dietary calcium may protect against bowel cancer
risk of bowel cancer, according to a major study based on 10
different trials.
The findings contrast with evidence that dairy products can increase the risk of other cancers, such as breast and prostate, although only milk was linked with a decreased cancer risk in the new study.
Researchers from the Brigham and Women's Hospital in the US analysed the results from studies carried out in five different countries, involving around half a million people, 5,000 of whom developed bowel cancer.
They report in this week's Journal of the National Cancer Institute (vol 96, no 13, 1015-1022) that the more milk people drank, the less likely they were to have bowel cancer.
People with an intake between 70-174g had a 6 per cent lower risk than those drinking less than 70g. The risk decreased further to 12 per cent for those with an intake of up to 249g and to 15 per cent lower risk for those with an intake of more than 250g daily.
The study did not find a significant impact on risk from other dairy foods such as cheese and yoghurt.
Bowel cancer, also known as colorectal cancer, is the third most common form of the disease worldwide.
Studies in animals have suggested that calcium may reduce the risk of colorectal cancer although research into the impact of calcium or dairy foods on bowel cancer risk has been inconclusive. Calcium is also known to help combat the risk of colon cancer.
The new study also showed that calcium intake was inversely related to the cancer risk. The relative risk for the highest versus the lowest quintile of intake was 0.86 for dietary calcium and 0.78 for dietary and supplemental sources combined. These results were consistent across studies and sex, said the researchers.
This suggests that increasing calcium intake to 1,000mg a day or more could result in 15 per cent fewer cases of bowel cancer in women and 10 per cent fewer cases in men.
Researchers do not yet understand the mechanism by which milk could prevent cancer.
A diet rich in fruit and vegetables and fibre has also been shown to have a protective effect on the disease.
