What are the first signs of colon cancer? Common symptoms and how to prevent

Colon cancer is one of the most common cancers in the United States and cases among younger adults are rising. Early detection is critical, as symptoms may not appear until the cancer has progressed.

"It's important for people to realize that colon cancer is undergoing an age shift, meaning that there are more young people, particularly under the age of 50, being diagnosed with colon cancer," said Dr. Arif Kamal, chief patient officer of the American Cancer Society.

Signs and symptoms of colon cancer

The first sign to look for is abnormal bleeding. Knowing if there is blood in your stool can be somewhat tricky, as blood can vary in appearance — from bright red to dark or tarry — depending on where it originates in the colon.

Blood changes color over time. If the bleeding begins in the earlier parts of the colon, Dr. Kamal said it may turn from bright red to dark or brown.

Other colorectal cancer signs and symptoms include persistent changes in bowel habits, such as diarrhea, constipation, narrow stools, or still feeling that you need to have a bowel movement despite already having one.

If food isn't passing through the colon normally, that could be a sign something is obstructing the path, Dr. Kamal said. Abdominal bloating, pain and unexplained weight loss are also red flags.

Though colon cancer has traditionally affected older adults, more cases are occurring in younger individuals. Dr. Kamal said, emphasizing that people with a family history of colorectal or gastrointestinal cancers have an increased risk.

"While colon cancer does happen in people of all ages, I would tell you the youngest person I've seen was in their teenage years," Dr. Kamal said.

Screening for colon cancer

Early detection significantly increases the chances that a person will recover from cancer. For colorectal cancers, screening through a colonoscopy remains the most important tool.

For people at average risk for colorectal cancer, the American Cancer Society recommends screening begin at age 45.

"You're putting a long, thin camera into the colon to look around. What you're looking for is polyps, those abnormal, precancerous, or cancerous growths," Dr. Kamal said. "The benefit of a colonoscopy is that if you see something abnormal — right then and there, you can cut it out and take it out."

"The idea is to find a precancerous growth before it ever turns into cancer," Dr. Kamal said.

At-home stool tests are also available for people hesitant about colonoscopies. These tests detect either hidden blood or abnormal DNA in the stool.

If results are positive, a colonoscopy is necessary for confirmation and removal of any precancerous growths, Dr. Kamal said.

Prevention of cancer

There are factors that increase your risk that you can't control but there are many that you can control to prevent colorectal cancer:

• Eat a healthy, balanced diet by increasing intake of fruits, vegetables and whole grains while limiting red and processed meats.
• Exercising — increasing the amount and intensity of physical activity helps reduce risk.
• Maintain a healthy weight. Obesity is a known risk factor.
• Quit smoking. Long-term smoking increases colorectal cancer risk, along with other cancers.
• Limit alcohol consumption. Moderation is key.
• Get enough calcium and vitamin D. Some studies suggest these nutrients may help protect against colon cancer, but talk to your doctor before taking supplements.
• Consider taking aspirin or nonsteroidal anti-inflammatory drugs under medical supervision.

Many people may need screening before the standard age of 45, especially if they have a family history of colon or other gastrointestinal cancers, Dr. Kamal said.

The American Cancer Society offers the free Cancer Risk 360 assessment tool to help assess risk.