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Red Meat, Obesity Raise the Risk of Colon Cancer


Two new research studies have added weight to the evidence that both the consumption of red meat and excess weight contribute to the increased risk of developing colon cancer.

A team from the Division of Cancer Epidemiology and Genetics at the US National Cancer Institute (NCI) in Rockville MD reviewed data from a cohort of over 300,000 men and women and reviewed the detailed questionnaires by the participants about the types of meat that they consumed and how it was cooked. After seven years of follow-up, there were 2,710 cases of colon cancer in the group.

Those who ate the most red and processed meat showed a significantly higher risk of developing colorectal cancer than those in the bottom quintile who consumed the least amount of meat. In a separate study conducted in 2005 and published in the Journal of the American Medical Association, high consumption of meat was described as 3 or more ounces per day for men and 2 or more ounces for women. The average American eats about 5 ounces of red meat per day. Eating red meat only a couple of times a week was considered low consumption.

The researchers were particularly interested in three compounds in the meat: heme iron, nitrate/nitrite, and heterocyclic amines. Heme iron is particularly high in red meat and nitrates are mostly found in processed meats such as salami or hot dogs. Heterocyclic amines are produced when the meat is cooked at a high temperature and are known to be mutagenic, meaning that they can alter DNA thus increasing the rate of cell production that can lead to cancer. All three compounds were found to have a positive association with colorectal cancer.

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This study was published in the March journal Cancer Research.

Researchers out of the Epidemiology Research Program at the American Cancer Society in Atlanta studied the association between obesity and colorectal cancer. The scientists performed a case-control study of subjects with colorectal cancer and their unaffected, sex-matched sibling. They evaluated weight and tumor microsatellite-stability (MSI) status, which indicates 5-year survival rate.

A body mass index of 30 or more was positively associated with the overall risk of colorectal cancer for both men and women. Obesity was also more closely associated with MSI-low or MS-stable colorectal tumors, which means that those patients had a lower survival rate.

An earlier study by the Mayo Clinic found similar results. Obesity increased the risk of death from colon cancer by 35% in men and 24% in women. Compared to normal weight patients, the obese were also found to have more recurrence and metastases.

This study was published online in the Journal of the National Cancer Institute.