High Blood Sugar Seems to Invite Colon Cancer

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Elevated blood sugar levels may increase women's risk of developing colon cancer, a new study suggests.

Of the postmenopausal women who were studied, those with the highest blood sugar levels were nearly twice as likely to develop cancer of the colon or rectum over a 12-year period as women with the lowest levels. None of the study subjects had sugar levels high enough to classify them as diabetic.

The findings may explain why obesity, which often goes hand-in-hand with high blood sugar, also raises a person's risk factor of colorectal cancer, the researchers said.

The study highlights the importance of maintaining a healthy weight, eating a good diet and getting exercise, all of which lower the risk of colorectal cancer, said study researcher Geoffrey Kabat, an epidemiologist at Albert Einstein College of Medicine in New York City.  

The study was published online today (Nov. 29) in the British Journal of Cancer.

Colon cancer risk

This year about 141,000 Americans will be diagnosed with colorectal cancer and 49,000 will die of it, the National Cancer Institute has projected.

Previous studies examined the effects of high blood sugar and the hormone insulin on colorectal cancer risk, but results from these studies were inconsistent.

Kabat and colleagues analyzed information from about 4,500 women ages 50 to 70 who were part of the Women's Health Initiative — a large study examining the most common causes of death and poor health in postmenopausal women. The new analysis focused on data gathered over 12 years, including the results of blood sugar level tests conducted several times during this period.

Participants were divided into three groups based on their blood sugar levels at the start of the 12 years (high, middle and low). By the end of the study period, 81 women had developed colorectal cancer. Of these, 35 were from the "high" group, and 18 were from the "low."

Those with consistently high blood sugar levels over time also were found to have an increased risk of colon cancer, the researchers said.

How sugar may harm colon cells

High levels of blood sugar, or glucose, may directly fuel the growth of cancer cells, or they could be a marker for other factors, such as increased levels of inflammation, that in turn increase the colon cancer risk, the researchers said.

More studies are needed to find the exact way high blood sugar levels increase the risk of this cancer, Kabat said.

No link was found between insulin levels and colorectal cancer risk.

Pass it on: A healthy weight, diet and exercise may reduce your risk of colon cancer by keeping blood sugar levels in check.

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Rachael Rettner

Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.