NEW YORK (CBSNewYork) — The American Cancer Society said young adults are dying from colon and rectal cancers at an increasing rate.

As CBS2’s Dr. Max Gomez explained, it’s happening at an age when they should start getting screened.

Colon cancer strikes about 140,000 Americans each year.

The overall rates for colorectal cancer have been going down for several decades with the exception of one group; young white patients.

The reason is a mystery, but there are things that can be done to buck that trend.

Each pregnancy for Chaya Biskin-Sitko seemed to get harder and more painful, but it took years for her doctors to find what was working.

“I’ve never even considered colon cancer as a thing, I thought old men get that,” Biskin-Sitko said.

The 33-year-old mother of three is one of a growing number of young people diagnosed with colorectal cancer, according to a new American Cancer Society study in the Journal of the Amereican Medical Association

It shows colon cancer rates have increased in white individuals ages 30 to 54 — this after decades of decline.

“Not only are the incidence rates going up — that’s been previously reported — but mortality rates in the 20 to 54-year-old population are also going up,” Dr. Alok Khorana said.

The problem is that the reasons why are not at all clear, although there are theories.

“Some of it may be due to the fact that there have been changes in young people, in the millennial generation, in terms of a more sedentary lifestyle, dietary changes, obesity may play a role, but that is not really clear,” Dr. Andrea Cercek said.

Gastroenterologist and CBS News Senior Medical Editor, Dr. John Lapook said that while the study also found that colon cancer death rates for non-white patients have not gone up, their overall rate is still higher.

“Year to year yes, there’s been some increase in mortality in whites, but still overall, blacks are much more likely to die and to get colon cancer than whites,” he said, “You tend to get them at an earlier age, and they tend to be more deadly, and more advanced when they are discovered.”

That’s why the American College of Gastroenterology suggests blacks have a screening colonoscopy starting at age 45, as opposed to 50 for others.

More research is needed to determine who else should be targeted for earlier screening, including factors such as family history and changes in bowel habits.

The good news is that colonoscopies can actually prevent most colon cancers by finding and snipping polyps before they become cancerous.