Diet changes due to urbanization in South Africa are linked to microbiome and metabolome signatures of Westernization and colorectal cancer.

Transition from traditional high-fiber to Western diets in urbanizing communities of Sub-Saharan Africa is associated with increased risk of non-communicable diseases (NCD), exemplified by colorectal cancer (CRC) risk. To investigate how urbanization gives rise to microbial patterns that may be amenable by dietary intervention, we analyzed diet intake, fecal 16 S bacteriome, virome, and metabolome in a cross-sectional study in healthy rural and urban Xhosa people (South Africa). Urban Xhosa individuals had higher intakes of energy (urban: 3,578 ± 455; rural: 2,185 ± 179 kcal/d), fat and animal protein. This was associated with lower fecal bacteriome diversity and a shift from genera favoring degradation of complex carbohydrates (e.g., Prevotella) to taxa previously shown to be associated with bile acid metabolism and CRC. Urban Xhosa individuals had higher fecal levels of deoxycholic acid, shown to be associated with higher CRC risk, but similar short-chain fatty acid concentrations compared with rural individuals. Fecal virome composition was associated with distinct gut bacterial communities across urbanization, characterized by different dominant host bacteria (urban: Bacteriodota; rural: unassigned taxa) and variable correlation with fecal metabolites and dietary nutrients. Food and skin microbiota samples showed compositional differences along the urbanization gradient. Rural-urban dietary transition in South Africa is linked to major changes in the gut microbiome and metabolome. Further studies are needed to prove cause and identify whether restoration of specific components of the traditional diet will arrest the accelerating rise in NCDs in Sub-Saharan Africa.

Differences in Fecal Gut Microbiota, Short-Chain Fatty Acids and Bile Acids Link Colorectal Cancer Risk to Dietary Changes Associated with Urbanization Among Zimbabweans.

The incidence of colorectal cancer (CRC) is gradually rising in sub-Saharan Africa. This may be due to dietary changes associated with urbanization, which may induce tumor-promoting gut microbiota composition and function. We compared fecal microbiota composition and activity in 10 rural and 10 urban Zimbabweans for evidence of a differential CRC risk. Dietary intake was assessed by a food frequency questionnaire. Fecal microbiota composition, metabolomic profile, functional microbial genes were analyzed, and bile acids and short chain fatty acids quantified. Animal protein intake was higher among urban volunteers, but carbohydrate and fiber intake were similar. Bacteria related to Blautia obeum, Streptococcus bovis, and Subdoligranulum variabile were higher in urban residents, whereas bacteria related to Oscillospira guillermondii and Sporobacter termitidis were higher in rural volunteers. Fecal levels of primary bile acids, cholic acid, and chenodeoxycholic acid (P < 0.05), and secondary bile acids, deoxycholic acid (P < 0.05) and ursodeoxycholic acid (P < 0.001) were higher in urban residents. Fecal levels of acetate and propionate, but not butyrate, were higher in urban residents. The gut microbiota composition and activity among rural and urban Zimbabweans retain significant homogeneity (possibly due to retention of dietary fiber), but urban residents have subtle changes, which may indicate a higher CRC risk.

Impaired gastric acid and pancreatic enzyme secretion in patients with Crohn's disease may be a consequenece of a poor nutritional state.

INTRODUCTION: Impaired pancreatic function has been reported in Crohn's disease, the cause of which is uncertain. This study investigated the effect of malnutrition, and subsequent re-feeding, on digestive function and protein synthesis in Crohn's disease patients. METHODS: Gastric acid and pancreatic secretion studies were performed on malnourished Crohn's patients before, and after a period of intensive nutritional support. Whole body, as well as pancreatic enzyme protein synthesis was investigated by [14C]leucine isotope incorporation studies. Results were evaluated in comparison to normal healthy volunteers. RESULTS: The mean body mass index (BMI) of the Crohn's patients was 14.14 kg/m2. The Crohn's patients had reduction in the secretion of gastric acid (7.36 versus 25.53 mEq/h; P < 0.01), and the pancreatic enzymes, amylase (759.6 versus 2305 U/h; P < 0.01), lipase (33.01 versus 118.6 U/h; P < 0.01) and trypsin (97.43 versus 341.4 U/h; P < 0.01). Resting energy expenditure (REE), expressed in relation to body mass, was greater in the malnourished Crohn's disease patients (38.25 versus 25.36 kcal/kg/d; P = 0.01). Total body protein synthesis was reduced (2.82 versus 4.39 g protein/kg/d; P < 0.05), with significant impairment in the synthesis of pancreatic enzymes, and reduction of zymogen stores. Following re-feeding, the BMI of the Crohn's patients improved to 16.80 +/- 0.66 kg/m2. Pancreatic enzyme synthesis improved, with significant increase in pancreatic enzyme stores and secretion, to levels similar to control values. Gastric acid secretion also improved, although still lower than the control value. CONCLUSION: Malnutrition may play a significant role in the impairment of gastric acid and pancreatic secretion in Crohn's disease patients.