Wed. Apr 14th, 2021
  • Colorectal cancer (CRC) remains the third most common cause of malignancy-related death in men and women in the United States.
  • It is estimated that 134,490 new cases and 49,190 deaths occured in 2016.
  • Among all racial and ethnic groups, African-American men and women continue to have the highest rate of death and shortest survival for CRC.
  • African Americans have the highest mortality rate of CRC of any ethnic group in the United States.  
  • African Americans also are often diagnosed at a younger age (median ages, 66 and 70 years for African American men and women compared with 72 and 77 years for white men and women, respectively)
  • Moreover, African Americans are two times more likely to be diagnosed with CRC before the age of 50 years, which justified the recommendation to begin endoscopic screening at the age of 45 years instead of 50 years. 
  • Some of this difference can be explained by tumor stage and socioeconomics, but the disparity remains even after accounting for tumor stage at diagnosis and after adjusting for socioeconomics, comorbidities, and treatment. The effect of body mass index on survival was assessed, and although it had an effect on survival, it was determined not to contribute to the disparity.  

Medical Study Results: Differences between African Americans & South African Blacks

  • Incidence rates of CRC are vastly different for African Americans (60 per 100,000 per year) and South African blacks (5 per 100,000 per year). 
  • Of the many differences that characterize the environment for these different individuals, diet can play an outsize role in the incidence rates for CRC. 
  • The diet for rural South African blacks is highly enriched in fiber and low in meat and fat, whereas the Western diet is low in fiber and high in meat and fat.
  • O’Keefe and colleagues conducted a diet switch in which they gave Pittsburgh African Americans the traditional South African black diet, whereas they gave rural South African blacks the Western diet. They then examined changes in the gut microbiome and fecal metabolites. Reciprocal changes were observed in the gut microbiome and the metabolome within 2 weeks of diet switch. 
  • African Americans receiving the high-fiber, low-fat diet exhibited increases in the abundance of microbial species involved in fiber fermentation, including species that metabolize butyrate and other short-chain fatty acids and the hydrogenotrophic microbes that remove hydrogen, including methanogens, acetogens, and sulfate-reducing bacteria. Concomitantly, there was suppression of microbial species that process bile acids, including bile acid deconjugators and the pathogenic sulfidogenic bacteria Bilophila wadsworthia and Fusobacterium nucleatum
  • South Africans receiving the low-fiber, high-fat diet exhibited the opposite pattern (ie, a lower abundance of species engaged in saccharolytic fermentation and higher bile acid deconjugating species). In addition, there were also reciprocal changes in gut epithelial cell proliferation, which is a marker for cancer development.  

What We can Do:

  • It is estimated that genetic factors contribute as much as 35% to the overall risk of CRC. Our understanding of genetic risk factors is anchored in mendelian genetics (ie, in single-gene defects that are associated with a high risk of CRC development). Mutations in the adenomatous polyposis coli (APC) gene are linked to familial adenomatous polyposis.
  • 90 percent of all colorectal cancer cases and deaths are preventable by removing polyps and cancer can be successfully treated — and often cured — when detected early. That is why screening for prevention and early detection is so important.
  • Experts suggest that African Americans get screened beginning at age 45. If you have a personal or family history of colorectal cancer, colorectal polyps or inflammatory bowel disease, talk with your health care professional. You may need to be tested earlier or more frequently.
  • Colonoscopy, when performed by a well-trained endoscopist, gastroenterologist or surgeon, is the most effective screening test.
  • Eat lots of vegetables, fruits, and whole grains. Diets that include lots of vegetables, fruits, and whole grains have been linked with a decreased risk of colon or rectal cancer. Eat less red meat (beef, pork, or lamb) and processed meats (hot dogs and some luncheon meats), which have been linked with an increased risk of colorectal cancer.
  • Get regular exercise. If you are not physically active, you may have a greater chance of developing colon or rectal cancer. Increasing your activity may help reduce your risk. Learn more about how to meet diet and exercise goals at
  • Watch your weight. Being overweight or obese increases your risk of getting and dying from colon or rectal cancer. Eating healthier and increasing your physical activity can help you control your weight.
  • Don’t smoke. Long-term smokers are more likely than non-smokers to develop and die from colon or rectal cancer. If you smoke and you want to quit, or know someone else who does, see the American Cancer Society guide to quitting tobacco, or call us at 1-800-227-2345. Getting help increases your chances of quitting successfully.
  • Limit alcohol. Alcohol use has been linked with a higher risk of colorectal cancer. The American Cancer Society recommends no more than 2 drinks a day for men and 1 drink a day for women. A single drink amounts to 12 ounces of beer, 5 ounces of wine or 1½ ounces of 80-proof distilled spirits (hard liquor).


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