Dr. Cedrek McFadden is a physician with GHS.
At the moment, Kaiser recommends average-risk patients begin screening at 50 with either an annual test to check for blood in stool or a colonoscopy every 10 years.
"There is compelling evidence that the optimum age to start is now 45", Dr. Richard Wender of the ACS told NPR, noting a sharp increase in deaths from colon and rectal cancers among men and women under age 50.
The American Cancer Society urged people to talk with their doctors about which kind of screening to pursue, based on risk factors like family history, diet, alcohol consumption and exercise patterns.
Dr. McFadden says if you have symptoms like bleeding, changes in bowel habits or abdominal pain, you should be screened right away, no matter your age. "We see a lot of younger patients", he said.
Other groups, including the independent and volunteer U.S. Preventative Services Task Force of specialists, maintain their recommendation that screenings start at 50.
According to Elena Ivanina, a gastroenterologist at Lenox Hill Hospital in NY, the 51 percent increase in colorectal cancer among those under age 50 since 1994 is an "alarming" trend.
The data that influenced the American Cancer Society found that the lower screening age would result in about a 6 percent increase in the benefit of screening and would require a 17 percent increase in colonoscopies. Unlike classic optical colonoscopy, no sedation is needed, so virtual CT colon cancer screening can be performed in the middle of a work day.
Rising rates of colon cancer and deaths in younger people led to the updated guidelines that were released on Wednesday.
"I have come across so many people - whether it is survivors, patients, or families of patients - and so many of them are in their 30s and 40s", said Sanford.
O'Neil said catching colon cancer early increases the chances of controlling it. Every five years, a person could do a computed tomography colonography test (a scan like a CAT scan) or a flexible sigmoidoscopy scan (essentially a tube with a light and camera on it).
According to the ACS, there's still a "strong recommendation" that adults begin screening at age 50 - that wording means there's good evidence that doing so will help reduce mortality rates.
With these new findings, she suggests people refer to their insurance company and doctor to find out when they should get screened. But based on the ways colon and rectal cancers have started to affect younger people, the ACS determined that such a change is still important to recommend. He believes, eventually, the recommended age will be even younger.