The Role of Diet on Sulfidogenic Bacteria Composition among African Americans and non-Hispanic Whites

Background: African Americans (AAs) are diagnosed with (CRC) at earlier ages and have higher mortality. Diet high in red meat and animal fat is associated with increased CRC risk and this might be modulated through diet’s effect on gut microbiota. Hypothesis: There are significant differences in dietary intake specifically in consumption of animal protein and fat between AAs and NHWs, and abundance of sulfidogenic bacteria is higher in AAs due to consumption of diet high in animal fat and protein. Methodology: Sociodemographic, clinical and dietary data were collected. Mucosal biospecimens were obtained from the right and left colon for determination of sulfidogenic bacteria [Bilophila wadsworthia-specific dissimulatory reductase gene (dsrA-Bw) and pan-dsrA that detects all sulfate-reducing bacteria (SRB)] composition by qPCR. Regression analyses were completed to identify predictors of dsrA-Bw and pan-dsrA gene copy numbers (gcn) in AAs and NHWs while adjusting for key covariates. Results: Study included 146 subjects; 78 AAs and 68 NHWs. Mean age was 58.05 and mean BMI was 30.64. NHWs had higher education (0.008), income (0.025) and alcohol consumption (0.016) levels while AAs had higher BMI (0.033) and predominance of female subjects (0.041). AAs had higher % energy from fat (0.045) and meat (0.035) consumption while NHWs had increased dairy (0.020) and alcohol intake (0.030). There were no significant differences in gcn of dsrA-Bw and pan-dsrA between right and left colons. NHWs had significantly higher dsrA-Bw gcn in the right (p=0.009) and left colon (p=0.002) and numerically higher pan-dsrA-Bw gcn in the right (p=0.076) and left colon (p=0.055). In regression analyses in AAs, BMI was the only predictor of dsrA-Bw gcn (p=0.003) while BMI (p=0.049) and alcohol (p=0.024) were independent predictors of pan-dsrA gcn. In NHWs, alcohol use (p=0.007) was the only independent predictor of pan-dsrA gcn. Conclusion: Results underline existing disparities and significant differences in dietary intakes among AAs and NHWs. Alcohol use in AAs and NHWs and BMI in AAs are independent predictors of sulfidogenic bacteria gcn. If these results are confirmed in larger datasets, preventive strategies that address dietary differences and modify sulfidogenic bacteria composition can be developed especially for high risk populations.