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Pre-Diabetes Increases Colon Cancer Risk

Researchers Say Rising Insulin Levels Are to Blame
WebMD Health News

April 6, 2004 -- As people get heavier and less active, their insulin levels rise. They are on the way to diabetes, heart disease -- and colon cancer, a new study shows.

Here's a test. What disease do people risk if:

  • Their diet is high in calories, animal fat, and refined carbs?
  • Their diet is low in fiber?
  • They get little exercise?
  • They are overweight or obese?
  • They have a super-sized waistline?

Diabetes? Yes. Heart disease? Yes. Colon cancer? Yes.

It's never been clear exactly why colon cancer is on this list. Now Jing Ma, MD, PhD, of Harvard Medical School and Brigham and Women's Hospital in Boston, has a prime suspect: Insulin.

As people get fatter, their bodies begin to resist the effects of insulin. To compensate, their pancreases make more and more of the sugar-lowering stuff. Ma and colleagues now show that people whose bodies make the most insulin because of insulin resistance have the highest risk of colon cancer.

The researchers analyzed blood samples collected from 1982 to 1984 from a study of some 15,000 male doctors. Compared to 294 matched noncancer control subjects, the 176 men who eventually developed colon cancer tended to have higher levels of an insulin by-product known as a C-peptide -- an indicator of insulin levels.

In their study, men with the highest C-peptide levels (levels of 0.74 or greater) had a 2.7-fold increased risk of colon cancer compared with those with the lowest C-pepitde levels. The findings appear in the April 7 issue of the Journal of the National Cancer Institute.

"Our data ... support the hypothesis that elevated long-term insulin production is one underlying mechanism to link dietary and lifestyle risk factors with colorectal cancer risk," Ma and colleagues write. "[They] also provide a strong biologic argument that avoiding or reducing the modifiable risk factors -- such as being overweight, being physically inactive, and following the Western dietary pattern -- could effectively decrease the risk of colorectal cancer and the risk of type 2 diabetes and cardiovascular disease."

SOURCE: Ma, J. Journal of the National Cancer Institute, April 7, 2004; vol 96: pp 546-553.

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