The American Cancer Society (ACS) is urging people to start having colorectal cancer screenings at age 45, not 50, as previously advised. 
Colorectal cancer is the 4th-most diagnosed cancer, and the 2nd leading cause of cancer deaths in the United States.
In the past, adults were advised to undergo screenings starting at age 50 to catch slow-growing malignancies. But in a paper published by the ACS on May 30, the group said that screenings should start 5 years sooner.
Dr. Richard Wender of the ACS said:
“There is compelling evidence that the optimum age to start is now 45. People born in the eighties and nineties are at higher risk of developing colon cancer, particularly rectal cancer, than people born when I was born back in the fifties. We just have to face reality. We just don’t know why it’s increasing.”
Wender noted that there has been a sharp increase in the number of deaths caused by cancers of the colon and rectum in adults under 50.
The U.S. Preventative Services Task Force and other groups continue to recommend age 50 as the best time to start getting screenings.
According to Dr. Robin Mendelsohn of New York City’s Memorial Sloan Kettering Cancer Center, her hospital has seen 4,000 new cases of colorectal cancer in patients under 50 in the last decade, and the majority of them don’t have any of the traditional risk factors, such as obesity, smoking, physical inactivity, or high-fat diets.
Disturbingly, many of them are remarkably healthy individuals. In many cases, according to Mendelsohn, their doctors told them they were “too young” to have cancer.
“[Some] are marathon runners who don’t eat red meat, don’t smoke, do everything right and say ‘Why did this happen to me?’”
A Rise Due to Improved Screenings? Maybe, Maybe Not.
Part of the uptick in diagnoses could be the result of improved screenings, the organization explained. If so, that would be a positive thing, as it means doctors are catching more cancer cases before they have a chance to become untreatable.
However, there is likely more to the story. The risk of developing colon cancer is twice as high as it was years ago, and the risk of developing rectal cancer is 5 times higher, according to Wender. 
There has been an increase in obesity in the U.S. Consider the following data from the U.S. Centers for Disease Control (CDC), published in a report titled “Obesity Trends Among U.S. Adults Between 1985 and 2010”:
- In 1990, among states that participated in the Behavioral Risk Factor Surveillance System, 10 states had a prevalence of obesity less than 10% and no states had prevalence equal to or greater than 15%. 
- By 2000, no state had a prevalence of obesity less than 10%, 23 states had a prevalence between 20%-24%, and no state had prevalence equal to or greater than 25%.
- By 2010, no state had a prevalence of obesity less than 20%. Thirty-six states had a prevalence equal to or greater than 25%; 12 of these states (Alabama, Arkansas, Kentucky, Louisiana, Michigan, Mississippi, Missouri, Oklahoma, South Carolina, Tennessee, Texas, and West Virginia) had a prevalence equal to or greater than 30%.
Wender said that “we don’t think that explains the entire change. There is a great deal of interest and a lot of research beginning to try to answer that question.” 
Some of the other culprits researchers are investigating include over-the-counter anti-inflammatory drugs, antibiotics, and antidepressants, in addition to multiple vitamins, probiotics, and other dietary supplements.
In the report, the ACS said the best methods for colorectal cancer screenings are colonoscopies, visual tests, and a high-sensitivity stool-based test. In addition, the organization said it categorized screenings for adults ages 45-50 as a “qualified recommendation,” while tests for people over 50 are categorized as a “strong recommendation.” 
The good news is that the rates of colorectal cancer deaths have been falling for decades, thanks, in part, to better screening and treatment methods. 
However, this year an estimated 140,000 Americans are expected to be diagnosed with colorectal cancer, and about 50,000 may die from it.
 CBS News