Links between diabetes and cancer: An insight

New Delhi: It may sound exaggerated but the unprecedented growth in Type-2 diabetes over the past 15 years and the deadly rise of cancer have a few common -- some even modifiable -- risk factors linked to how we lead our daily lives, health experts say.

These include age, sex, obesity, physical activity, diet, alcohol and smoking.

"In 80-90 per cent cases of cancer occurrence, environmental factors, particularly lifestyle disorders, are responsible, which also account for higher number of diabetes cases," Anil Kumar Dhar, oncologist at Gurgaon's Columbia Asia Hospital, told IANS.

"Appropriate changes in lifestyle have shown reduction in mortality and morbidity of both the diseases," Dhar added.

According to the latest World Health Organisation (WHO) estimates, the number of people diagnosed with diabetes in India doubled to 63 million in 2013 from 32 million in 2000 -- nearly 100 per cent in 13 years. The number is expected to rise to 101 million by 2030.

"As reported by WHO, more than one million new cases are reported in India while about 680,000 people die due to cancer in India," Minister of State for Health Anupriya Patel said in a written reply in the Rajya Sabha last month.

According to endocrinologist Purnima Agarwal of Jaypee Hospital, Noida, diabetes and cancer are common diseases with tremendous impact on health worldwide and epidemiologic studies demonstrated that the people with diabetes are more likely to develop cancer.

"However, the exact biological link between cancer and diabetes is still incompletely understood," she said.

There are two possible links between the two diseases -- general mechanism and tissue-specific mechanism.

The general mechanism is linked to insulin resistance which is a hallmark of Type-2 diabetes. "Insulin is a growth factor with predominantly metabolic action but it can have mitogenic effects that can lead to cancer," Agarwal explained.

"Hyperglycemia or excess of glucose in the bloodstream, chronic inflammation and obesity can also lead to oxidative stress which can increase the risk of cancer," Agarwal told IANS.

Among the tissue-specific mechanisms linking diabetes with cancer, she mentioned that liver and pancreatic cells exposed to higher insulin concentrations could be the cause of higher incidence of these cancers in diabetic patients.

Various changes secondary to diabetes like fatty liver, increased chances of Hepatitis B and C infections can also contribute to the increased risk.

"Type-2 diabetes is associated with liver, pancreas, kidney, breast and endometrium cancers," noted Siddharth Kumar Sahai, an oncologist at Gurgaon's Paras Hospitals.

The common lifestyle factors that can contribute to both diabetes and cancer were recently discussed in a major symposium at the American Association for Cancer Research (AACR) annual meeting where University of Colorado Cancer Center investigator Tim Byers described research showing the link between cancer, diabetes and cardiovascular disease.

"Obesity leads to a chronic inflammatory state and circulating growth factors that have adverse effects on the heart and can also contribute to the development of cancer. But we tend to study these things in isolation, by disease and not by risk factor," Byers told the gathering.

Overweight/obesity is a well-known risk factor for diabetes mellitus. "There is growing evidence that weight gain is associated with increased risk of some cancer like breast cancer, colon cancer and endometrial cancer," Agarwal noted.

Similarly, lack of physical activity increases the risk for both Type-2 diabetes and cancer.

"Epidemiological observational studies consistently indicated that higher level of physical activity is associated with lower risk of colon, breast and endometrial cancer," Agarwal said.

Reducing the risk of diabetes and cancer has to do a lot with what we eat. "Diet rich in red and processed meat, less of fibre is associated with high risk of both Type-2 diabetes and cancer," she noted.

Another risk factor that diabetes shares with cancer is smoking. It is estimated that worldwide tobacco smoking accounts for 71 per cent of lung cancer death and studies suggested that smoking is also independent risk factor for development of diabetes mellitus.

In addition, it increases the risk of complications of diabetes mellitus like cardiovascular disease and retinopathy, the experts said.

Alcohol consumption in moderate amounts increases the risk of cancers in oral cavity, oesophagus, liver and colon. Excess consumption of alcohol is also a risk factor for Type-2 diabetes.

Understanding the similarities and differences in how these risk factors create cancer and diabetes could aid the ways we prevent these deadly diseases, the experts suggested.