According to the American Cancer Society, about 135,000 people will be diagnosed with colorectal cancer this year, and about one in seven of them will be under the age of 50. Researchers have also predicted that cases of colon cancer among people age 20 to 34 would increase 90% by 2030. Researcher Dr. Yi-Qian Nancy You adds that about a third of the cases can be attributed either to a genetic condition or a family history of the disease. But for the remaining two-thirds, it’s unclear. She says, “We don’t know if it’s diet or lack of exercise or other factors.”
WebMD, December 2016