Why Does Diabetes Increase Cancer Risk?

According to the American Diabetes Association, there is a link between diabetes type 2 and certain types of cancer, particularly liver, pancreas, colon, bladder, breast, uterus, stomach, and kidney cancers. Why is diabetes associated with cancer and how can someone with diabetes prevent the development of cancer? Although this connection is not fully understood, there are some ways to explain how these two conditions are linked. 

Some reasons why diabetes is linked with cancer

Diabetes and cancer share certain risk factors, increasing the odds to see both conditions in certain individuals. For example, the age factor- both diabetes type 2 and cancer are more prevalent in older adults. The male gender could be another factor, as men have slightly more chances to get diabetes and colon, liver, and pancreatic cancer. 

Some ethnic groups, including African Americans, Native Americans, Latinos, and Pacific Islanders have an increased risk of diabetes and some cancers. 

Being overweight and leading a sedentary life increases the chances of developing diabetes. Obesity is also linked with several types of cancer, particularly liver, pancreatic, colon, breast, endometrial, and stomach cancers. 

Finally, unhealthy habits such as smoking and excess drinking are associated with increased risks of diabetes type 2 and some cancers. 

The latest research on the link between diabetes and cancer

Abnormal glucose metabolism- which is characteristic of diabetes- is emerging as an independent risk factor for the development of certain types of cancer and may also affect the prognosis of cancer.

For example, about 80% of the cases of pancreatic cancer are linked with diabetes and impairments in glucose tolerance. Furthermore, there is a 94% risk of pancreatic cancer in those with diabetes compared to individuals who do not have diabetes. Some health experts suggest that diabetes may be a consequence of undiagnosed pancreatic cancer, while others believe diabetes is a cause, not a consequence of pancreatic cancer. 

When it comes to liver cancer, people with diabetes are almost two times more likely to be diagnosed with this form of cancer compared with those without diabetes. Other liver diseases like hepatitis due to hepatitis B virus, excess alcohol, and fatty liver may play a role as well.

Diabetes seems to affect the prognosis of colon cancer. According to one study related to colorectal cancer, people with colorectal cancer and diabetes have a 5 year shorter survival compared to individuals without diabetes. Having diabetes does not seem to have a negative impact on lung cancer survival.

Based on research studies, there are certain factors that may be responsible for the relationship between diabetes and cancer.  High blood sugar levels and inflammation are key factors in the progression of diabetes to cancer. Abnormal glucose metabolism directly promotes the formation of cancer cells and also indirectly through a hormone called insulin-like growth factor 1 or IGF-1. In addition, diabetes is associated with increased free radicals and oxidative stress, which promote DNA damage and subsequent cancer. 

Although studies found mixed results, some research suggests that insulin therapy may be associated with an increased risk of overall cancer in general, and pancreatic and colorectal cancer in particular.  Some oral diabetes drugs showed similar effects. 

Good news: Diabetes and the drug metformin  inversely correlated with some cancers

On the other hand, some researchers suggest a reduced risk of prostate cancer in individuals with diabetes. In fact, one study concluded that people with diabetes have a “significant” decrease in risk of developing prostate cancer. For women,  researchers noted a significantly decreased risk of gallbladder cancer in females with diabetes type 2. 

Unlike other diabetes oral drugs, the most commonly used oral drug, metformin, may help protect against cancer and decrease the risk of death. There is increasing evidence showing that metformin offers protection against breast cancer and may prolong the life of a person who has both diabetes and cancer. Metformin is one of the most researched drugs studied for its ability to extend life. So far, animal studies show promising results. 

More good news

In addition to keeping diabetes well controlled with medication, adopting a healthy lifestyle can have a positive impact on both diabetes and cancer prevention. For example, many studies show a strong and inverse relationship between Mediterranean diet adherence and chronic illnesses like diabetes, heart diseases, and cancer. This diet is rich in antioxidants which help fight inflammation, free radicals, and the formation of cancer cells. Regular exercise, sleeping well, and managing stress can also help stay as healthy as possible and better cope with chronic illnesses. 

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