Expert-reviewed by Ashwini S.Kanade, Registered Dietician and Certified Diabetes Educator with 17 years of experience
Having diabetes makes one more prone to developing additional health complications later in life. Some of these complications are well known, such as kidney disease and heart disease, but there are some that you might not be aware of.
New research has found that people with diabetes have an increased risk of cancer of the large intestine (known as colorectal cancer).  People with diabetes have a 30% higher risk of developing colorectal cancer than those without diabetes.  This risk is further increased by obesity which, unfortunately, is not uncommon among people with diabetes. The good news, however, is that this risk is reversible.
What does colorectal cancer look like?
Colorectal cancer, which is cancer of the large intestine (the colon and the rectum), has somewhat vague symptoms such as anemia, bleeding from the rectum, pain in the abdomen, etc. But these symptoms are not observable until the cancer has reached an advanced stage. Fortunately, regular check-ups, which can include certain stool tests and colonoscopy, can easily detect the cancer. Indeed, medical guidelines recommended that individuals who are at a high risk for developing colorectal cancer—for instance, if someone in the family has it—should get screened every few years. Even if diagnosed, colorectal cancers in most cases are easily treated through surgery.
How is diabetes related to colorectal cancer?
One of the main causes of type 2 diabetes is insulin resistance: the cells fail to respond to normal levels of insulin, which increases blood sugar levels. To compensate for this increased blood sugar, insulin levels in the blood also increase. This is known as hyperinsulinemia, and is known to cause colorectal cancer.  In other words, just having type 2 diabetes, which inherently includes the risk of hyperinsulinemia, causes an increased risk of colorectal cancer.
It is critical for people with diabetes to exercise good control over their blood sugar levels to reduce chances of hyperinsulinemia and thus colorectal cancer.
Also, read about the increased risk of breast cancer for diabetics.
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What besides diabetes can increase the risk?
- A low fibre diet (risk of cancer is lower in individuals who have high fibre in their diet).
- A “Western” diet, which includes high intakes of red meat (beef), refined grains (pasta, white bread, etc.), and sugar (desserts). 
- Excessive intake of alcohol (the guidelines recommend no more than one glass of a drink per day that is relatively low in alcoholic content, such as beer or wine.)
Are men and women equally affected?
The risk of colorectal cancer increases in both men and women with diabetes, but it seems to be slightly higher in women than in men. In men, however, even the pre-diabetic state (which is fasting glucose between 100 and 125 mg/dL) carries an increased risk.
What is the role of weight?
Low or no physical activity and abdominal obesity (fat deposits concentrating around the waist) are associated with insulin resistance. Other factors that increase the risk of colorectal cancer among people with diabetes are a sedentary lifestyle and a high-calorie diet. The risk is further increased if the person has been obese for 4 years or more.
What can I do to lower my risk of colorectal cancer?
Strategies to reverse the increased risk should aim to lower insulin resistance and keep blood sugar under control. This can be achieved through diet, exercise, weight loss (if overweight/obese), and medications.
- Reduce or completely stop consuming foods that cause a spike in glucose or insulin levels. Refined grains are a perfect example of this.
- Increase your fibre intake.
- Avoid foods with a high glycemic index.
- For decades, scientists have been trying to determine which form of exercise and how much is ideal for decreasing insulin resistance. Although the case hasn’t been closed, it seems that moderate-intensity exercise 3-5 times a week totalling at least 120 min/week improves insulin sensitivity.
- Some studies suggest that vigorous exercise in short bursts (also known as high-intensity interval training) for 170 min/week gives better results.
Consult your doctor to discuss when you should get your screening scheduled. Remember that keeping your blood sugar levels under tight control will considerably lower your risk of not only colorectal cancer but also many other complications related to diabetes.
Disclaimer: The information we share is verified by experts and scientifically validated. However, it is not a replacement for a doctor’s advice. Please always check with your doctor before trying anything suggested on this website.
- Guraya SY. Association of type 2 diabetes mellitus and the risk of colorectal cancer: A meta-analysis and systematic review. World Journal of Gastroenterology: WJG. 2015 May 21;21(19):6026. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4438039/
- Peeters PJ, Bazelier MT, Leufkens HG, de Vries F, De Bruin ML. The risk of colorectal cancer in patients with type 2 diabetes: associations with treatment stage and obesity. Diabetes Care. 2015 Mar 1;38(3):495-502. http://care.diabetesjournals.org/content/38/3/495.short
- Meyerhardt JA, Niedzwiecki D, Hollis D, Saltz LB, Hu FB, Mayer RJ, Nelson H, Whittom R, Hantel A, Thomas J, Fuchs CS. Association of dietary patterns with cancer recurrence and survival in patients with stage III colon cancer. Jama. 2007 Aug 15;298(7):754-64. https://jamanetwork.com/journals/jama/fullarticle/208423