Does Smoking Cause Colorectal Cancer?

Tobacco and tobacco products remain leading causes of preventable death worldwide. Although most people know smoking causes lung cancer, fewer know it also increases colon and rectal cancer risk. Research shows that regular smokers are significantly more likely to develop colorectal cancer than people who have never smoked.

The Link Between Smoking and Colorectal Cancer

Scientific studies clearly show that smoking increases colon and rectal cancer risk. Years of smoking damage DNA in intestinal cells, triggering mutations in the process leading to cancer.

• Smokers' colorectal cancer risk is 15–30% higher.
• Risk rises further with heavy daily smoking and prolonged use of 20 years or more.
• Smoking increases both the chance of developing cancer and the likelihood that, at diagnosis, it is more advanced .

Risk Factors and Other Effects

According to the American Cancer Society (ACS), other colorectal cancer risk factors include:

• Overweight or obesity
• A diet rich in red or processed meat
• Low vitamin D levels
• Moderate-to-heavy alcohol consumption
• Type 2 diabetes
• Being over 50
• American Indian, Alaska Native, African American, or Ashkenazi Jewish ancestry
• Previous gallbladder removal (cholecystectomy)
• A history of colorectal cancer, colorectal polyps, inflammatory bowel disease (IBD), or pelvic/abdominal radiotherapy
• A family history of adenomatous polyps or colorectal cancer
• Inherited syndromes such as familial adenomatous polyposis or Lynch syndrome

Quitting Smoking and Reducing Risk

Quitting is one of the most effective ways to reduce colon and rectal cancer risk. Studies show that:

• After quitting, within 5–10 years, colorectal cancer risk decreases substantially.
• After long-term cessation, risk approaches that of never-smokers.
• Quitting also reduces the risk of other cancers, cardiovascular disease, and COPD.

Prevention and Screening

Lifestyle and screening both matter for colorectal cancer prevention and early detection.

When Should You See a Doctor?

The American Cancer Society (ACS) recommends regular colorectal cancer screening starting at age 45 .

However, anyone noticing possible colorectal cancer signs or symptoms at any age should see a doctor.

These include:

• Changes in bowel habits, such as constipation or diarrhea, lasting more than a few days
• Blood in stool
• Black or red stools
• Bright red blood when wiping
• A persistent urge to pass stool after a bowel movement
• Abdominal pain or cramps
• Unintentional weight loss
• Fatigue
• Jaundice (yellowing of skin or the whites of the eyes)

Other health conditions can cause these symptoms. Always consult your doctor to determine their cause. Early colorectal cancer diagnosis and treatment can significantly improve the disease course.