The Cancer-Diabetes Connection

For most people, diabetes stems from problems with the production of insulin, a hormone made in the pancreas. When someone no longer makes insulin it's diagnosed as Type 1 diabetes; when someone doesn't make enough insulin or the body doesn't use it normally, it's Type 2. Either way, it can result in high blood glucose levels and cells that aren't getting the energy they need. In Type 2,  high blood sugar can also trigger the production of more insulin, leading to too much insulin in the blood.

The connection between signs of insulin resistance and cancer is strongest among certain types of cancers, including colon cancer and pancreatic cancer.

A 2006 study published in the Journal of the National Cancer Institute found that men who had signs of the highest insulin levels were almost three times more likely to develop colon cancer than men with the lowest levels. Other studies found increased risk in people with Type 2 diabetes and prediabetes.

Many studies have shown a link between pancreatic cancer and diabetes. Yet because pancreatic cancer and diabetes both involve the pancreas, evidence remains unclear on whether diabetes causes or results from the cancer.

Although the association is not as strong, studies have also linked diabetes to prostate, endometrial, liver and breast cancers.

High amounts of insulin, Type 2 diabetes and cancer all share a major risk factor: high body fat. Researchers also found that high body fat is convincingly linked to the increased risk of several cancers, including pancreatic and colorectal.

Excess body fat can lead to the pancreas producing excess amounts of insulin. And studies have shown that insulin stimulates cell proliferation and tumor growth. Also, high levels of insulin, independent of body fat, are linked to increased production of insulin and growth factor 1 (IGF-1), which plays a key role in promoting cancer cell growth.

In the same way that similar factors increase risks for both cancer and diabetes, there are similar ways people can lower their risk. Maintaining a healthy weight and physical activity can decrease the risk of cancer and diabetes.

For cancer, Americans could prevent approximately 100,500 cases of cancer annually if they maintained low body fat. For diabetes, a major study sponsored by the National Institutes of Health found that people at increased risk for Type 2 diabetes can significantly prevent or delay the onset of the disease by losing 5 to 7 percent of their body weight through increased physical activity and diet.