Many think that colon cancer is something that people aged over 50 should be worried about, but it pays to be on guard against the disease at a much earlier age, doctors say.

A study released Thursday by the Korean Society of Coloproctology found that over 20 percent of men in their 30s who underwent colonoscopies between 2009 and 2011 had one or more polyps, the primary seed of colon cancer.

It was a surprisingly high rate for the age group, which was regarded as less vulnerable, researchers said. Men in that age group showed a higher rate of 21.1 percent, than women (13.2 percent).

“The study shows that people in their 30s should no longer be considered a low-risk group,” said Oh Seung-taek, president of the coloproctogy body. “To effectively fight colon cancer, we need to advise people to start colon cancer screening from their 30s,” he added.

Existing guidelines recommend colon cancer screenings begin from the age of 50.

The study looked into nearly 150,000 patients who underwent colonoscopies at seven hospitals and clinics between 2009 and 2011. Of them, 36 percent was found to have one or more polyps and 0.5 percent were diagnosed with colon cancer.

Colon cancer, which is cancer of the large intestine, is the third most common form of cancer among Koreans, after stomach and thyroid cancer.

It accounts for 12.7 percent of all cancer incidences.

It often begins as a small, benign clump of cells known as a polyp in the large intestine or colon. Over time, this can develop into a life threatening cancer that can spread throughout the body. The larger the polyp is the higher the risk of cancer.

But the problem is that polyps can go unnoticed for a long time ― they are small and accompanied by few or no symptoms.

So doctors advise people to undergo colonoscopies or other forms of screening to catch polyps and remove the risk of cancer.

“Thus, this year's campaign against colon cancer has a particular focus on raising awareness of polyps,” Oh said.

Oh's KSC and Korean Cancer Association has designated September the month for colon cancer five years ago and has since rolled out various campaigns aimed at raising public awareness for early detection.

This month, nearly 70 hospitals and clinics throughout the country are planning free public lectures on colon cancer, offering tips on prevention, diagnosis and treatment of the disease.

Lifestyle changes to reduce your risk:

● Adopt a varied diet that includes fruits, vegetables and whole grains rich in vitamins, minerals, fiber and antioxidants.

● Quit smoking and excessive drinking and exercise every other day for at least 30 minutes.

● Maintain a healthy weight.

● Watch out for a change in bowel habits or constituency of the stool.

● Don't eat too much salty food and drink more than 1.5 liters of water a day.

By Lee Sun-young (milaya@heraldcorp.com)