Diabetes and Colon Cancer: What Is the Relationship?

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The American Diabetes Association’s guidelines for medical care now recognize a link between colon cancer and type 2 diabetes. Knowing how the two conditions are related can help those with diabetes or colon cancer and their healthcare providers better understand what can be done to reduce the risk of the other condition and/or manage both conditions.

This article talks about the connection between diabetes and colon cancer, the shared risk factors of both conditions, and how they can be treated and prevented to improve health and quality of life.

A woman speaking with a healthcare provider.

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Connection Between Diabetes + Colon Cancer

There are a few points of connection between diabetes and colon cancer. Some biological factors of diabetes affect the gut in a way that can stimulate cancer growth.

The three potential pathways that connect diabetes to colon cancer include:

  • Insulin resistance
  • High blood sugar
  • Inflammation

These are outlined below.

Hyperinsulinemia

Elevated insulin levels in the blood (hyperinsulinemia) due to insulin resistance may partly explain the association between diabetes and colon cancer.

Insulin is an important growth factor for cells in the colon. Therefore, too much insulin in the blood increases the amount of growth factor, which may stimulate tumor cell growth.

Hyperglycemia

Another potential link between diabetes and colon cancer is elevated blood sugar (hyperglycemia). High blood sugar levels can impact cellular metabolism, the immune system, and reactive oxygen species, all of which could contribute to cancer development in people with diabetes.

Inflammation

Inflammation plays a role in both type 1 diabetes and type 2 diabetes.

The diabetic inflammatory response has been associated with colon cancer through different cellular pathways that then lead to cancer growth. Furthermore, issues with inflammatory responses in the gut have been associated with an abnormal gut microbiome, worse gut inflammatory response, and colon tumor growth.

Risks

Having diabetes increases the risk of developing colon cancer. A 2015 study found that people with type 2 diabetes had a 1.3-fold increased risk of colorectal cancer.

Another study found that having diabetes increased the risk of colorectal cancer in a similar magnitude as having a family history of colorectal cancer. This risk was more likely among people who were diagnosed with diabetes before 50. This highlights the importance of early intervention to prevent and/or manage diabetes early on. 

Below are some risk factors associated with type 2 diabetes and colon cancer. Importantly, while some factors like genes are out of your control, most of these risk factors can be modified to reduce risk, putting some control back into your hands.

Genetic Variants

Research has shown that type 2 diabetes-related genetic variants affect the risk of developing colorectal cancer.

For example, one study found that people with type 2 diabetes who had the TCF7L2_rs7903146_T genetic variety had an increased risk of colorectal cancer. This genetic variant may impact colorectal cancer risk in different ways, including the reduced function of beta cells, which are responsible for secreting insulin to make glucose absorption possible.

Obesity

Obesity is a risk factor for both type 2 diabetes and colon cancer.

Obesity is considered a major cause of insulin resistance and is associated with hyperglycemia, both of which are tied to diabetes. In addition, colon cancer is one of the cancers most commonly associated with being overweight and obese.

Lifestyle Factors

Lifestyle factors are often involved in chronic conditions like diabetes and cancer. The association between type 2 diabetes and colon cancer is strongly influenced by a few shared lifestyle risk factors:

  • Physical inactivity
  • Smoking
  • Alcohol use

It’s important to note that while these are modifiable risk factors, it’s not always easy to change them, especially if addiction is at play. Talk to your healthcare provider if you have concerns about how your lifestyle may impact your risk of diabetes and colon cancer.

Treatment and Management of Diabetes With Colon Cancer

The relationship between diabetes and colon cancer is complex, which makes the treatment of both conditions at the same time also complex. However, research has explored ways to simultaneously manage both conditions through surgical and non-surgical methods. 

Surgery

Some people with colon cancer need surgery to manage the condition and keep cancer from growing. Surgery can damage some of the nerves in the colon, which could negatively affect incontinence, especially if some of the nerves are already affected by diabetes. This is something for the operating surgeon to consider before surgery.

Chemotherapy

5-fluorouracil (5-FU)-based chemotherapy is the main treatment for colorectal cancer. This therapy can cause hyperglycemia, which is an important consideration for healthcare providers treating people with diabetes and colon cancer.

Other potential effects of chemotherapy that are especially important considerations for people with diabetes include increased risk of:

Because the treatment and management of diabetes with colon cancer are complex, a healthcare provider must carefully consider the risks and benefits of treatment.

While the management of colon cancer may require special medical care, managing blood sugar can be done every day. Knowing what a healthcare provider may consider in the treatment plan can help you feel more informed about what it means to have both conditions.

Prevention

Some risk factors of diabetes and colon cancer are out of one’s control, like genetic factors or family history. However, many risk factors can be reduced through lifestyle changes, and many of these risk factors overlap.

Below are some shared preventative factors that have been shown to reduce the risk of colon cancer and diabetes:

  • Screening: According to the Centers for Disease Control and Prevention (CDC), the most effective way to reduce colon cancer risk is to get screened routinely, starting at age 45. Blood sugar tests are also an easy screening to help identify prediabetes and diabetes.
  • Diet: Eating a diet low in animal fat and high in fruits, vegetables, and whole grains is recommended to reduce the risk of some chronic diseases, including diabetes and colon cancer.
  • Physical activity: Studies have shown that physical activity is associated with a decreased risk of colon cancer. In addition, physical activity has been shown to lower A1C levels in people with type 2 diabetes, even without a significant change in BMI.
  • Alcohol: According to the CDC, the less alcohol you drink, the lower your risk of cancer. Drinking can also cause low blood sugar, which can be dangerous for people with diabetes, especially if taking insulin.
  • Smoking: Many studies have shown a causal link between smoking and health risks. The American Diabetes Association has smoking cessation as part of its treatment guidelines for people with diabetes and colon cancer.
  • Healthy weight: Being overweight can increase the risk of high blood sugar and type 2 diabetes. Maintaining a healthy weight is also important for reducing colon cancer risk. 

These key factors involved in the prevention of diabetes and colon cancer are also important for overall health. Talk with your healthcare provider about steps you can take to reduce your risk and support to help you move away from unhealthy behaviors like smoking.

Summary

Diabetes and colon cancer are both common conditions, and research has shown that diabetes can impact the risk of colon cancer.

The two conditions share some risk factors, some of which are changeable, like physical activity and diet. While simultaneous treatment of these two conditions may be complicated and require medical advice, prevention can be done at home every day through lifestyle changes.

A Word From Verywell

Chronic conditions are hard enough to manage in day-to-day life, let alone if you have two.

Management of diabetes and colon cancer may make the everyday kinds of things that much harder. But if you’re living with diabetes and colon cancer, know that you are not alone. These two conditions share risk factors, so it’s not uncommon for someone to have both.

Prevention is possible, but for some, it’s too late, or their risk is out of their control.

Treatment may seem complicated, but your healthcare provider can help you understand what can be done to manage these conditions to make you feel more in control and take back your quality of life.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Emily Brown, MPH
Emily is a health communication consultant, writer, and editor at EVR Creative, specializing in public health research and health promotion. With a scientific background and a passion for creative writing, her work illustrates the value of evidence-based information and creativity in advancing public health.