Why Do African Americans Get More Colon Cancer than Native Africans?

Abstract

The incidence of colorectal cancer (CRC) is dramatically higher in African Americans (AAs) than in Native Africans (NAs) (60:100,000 vs. <1:100,000) and slightly higher than in Caucasian Americans (CAs). To explore whether the difference could be explained by interactions between diet and colonic bacterial flora, we compared randomly selected samples of healthy 50- to 65-y-old AAs (n = 17) with NAs (n = 18) and CAs (n = 17). Diet was measured by 3-d recall, and colonic metabolism by breath hydrogen and methane responses to oral lactulose. Fecal samples were cultured for 7-alpha dehydroxylating bacteria and Lactobacillus plantarum. Colonoscopic mucosal biopsies were taken to measure proliferation rates. In comparison with NAs, AAs consumed more (P < 0.01) protein (94 +/- 9.3 vs. 58 +/- 4.1 g/d) and fat (114 +/- 11.2 vs. 38 +/- 3.0 g/d), meat, saturated fat, and cholesterol. However, they also consumed more (P < 0.05) calcium, vitamin A, and vitamin C, and fiber intake was the same. Breath hydrogen was higher (P < 0.0001) and methane lower in AAs, and fecal colony counts of 7-alpha dehydroxylating bacteria were higher and of Lactobacilli were lower. Colonic crypt cell proliferation rates were dramatically higher in AAs (21.8 +/- 1.1% vs. 3.2 +/- 0.8% labeling, P < 0.0001). In conclusion, the higher CRC risk and mucosal proliferation rates in AAs than in NAs were associated with higher dietary intakes of animal products and higher colonic populations of potentially toxic hydrogen and secondary bile-salt-producing bacteria. This supports our hypothesis that CRC risk is determined by interactions between the external (dietary) and internal (bacterial) environments.

Diet, microbiota, and microbial metabolites in colon cancer risk in rural Africans and African Americans

“…In sharp contrast, rural Africans rarely get the disease (3). Studies of ours have ascribed this difference to higher meat and fat intakes in Americans and to higher resistant starch intakes in Africans (4).…”

Disparities in colorectal cancer in African-Americans vs Whites: Before and after diagnosis

“…Fiber consumption is significantly associated with 50%-60% reduced risk of colorectal cancer in African Americans and non-significantly with 30% reduced risk of colorectal cancer in Whites [56] . Hydrogen response to 10 g of oral lactulose is significantly higher in the African-American than in the Caucasian American population implicating a difference in colonic bacterial metabolism between the two groups [57] . African Americans in all age groups seem to consume fewer mean daily servings of total dairy, milk, cheese, and yogurt than non-African Americans, and have lower mean intakes of calcium, magnesium, and phosphorus [58] .…”

Gut microbiome compositional and functional differences between tumor and non-tumor adjacent tissues from cohorts from the US and Spain

“…Only a small number of studies have compared the gut microbiome composition of CRC patients from different populations. A study comparing the microbiome of healthy individuals from a high CRC risk population (African-Americans) with a low risk population (Africans) 36,37 showed differences in the microbiome composition between the 2 populations, which probably reflect a diet high in fiber and less meat and fat for Africans compared to the African-American diet more comparable to the Western diet. The study found an over abundance of Prevotella, Succinivibrio, and Oscillospira in Africans and a predominance of the genus Bacteroides in African-Americans.…”