A study, published this week in Journal of the American Medical Association, indicates that vitamin D in the diet helps prevent colorectal cancer, while smoking and drinking alcohol increases the risk of getting the disease. Doctors also warn that people with no symptoms may still be stricken with colorectal cancer.
Previous studies have identified family history and abnormal growths, called colon polyps, as the main factors for colorectal cancer.
But a study of more than 3,000 volunteers turned up advanced colon tumors in one in 10 men, even though they had no symptoms.
Besides family history and colon polyps, a questionnaire found the men smoked and drank alcohol.
Lead author David Lieberman, a gastroenterologist with the U.S. Veterans Administration medical facility in Portland, Oregon, says the most significant risk appears to come from smoking.
"Either past or current," he said. "And this is a stronger risk factor than in some of the other studies that have been done. And that reinforces the fact that smoking isn't good for you in a number of ways, and isn't good for your colon."
Researchers also found that even smokers and drinkers who stopped, did not reduce their likelihood of developing colon cancer.
Dr. Lieberman hopes the findings result in a new set of testing guidelines that not only take into account family history of colorectal cancer and colon polyps, but smoking and drinking.
But he says the message remains the same.
"People need to go in for screening beginning at age 50 when they are feeling perfectly fine," said David Lieberman.
On the positive side, men who did not develop colon cancer had fiber-rich diets and ate foods containing a lot of calcium and vitamin D. Investigators have long suspected that vitamin D is protective, but the study results confirmed that.