Westernization of Diet and the Gut

Dr. Sören Ocvirk


Diets associated with a modern lifestyle in high-income countries are often characterized by low intake of dietary fiber and high consumption of fat and red meat. This “Western diet” pattern promotes fundamental changes in the human gut microbiota composition and metabolism, collectively increasing the risk of several non-communicable diseases (NCD) including obesity, diabetes or colorectal cancer. Being at the interface of gut microbe-host interactions, gastrointestinal health is clearly affected by diet-mediated dysbiotic traits of the gut microbiota. But to identify what features characterize a disease-associated (=dysbiotic) gut microbiota, we need to understand first how a healthy microbiota is defined, in particular in populations having a low NCD risk.  

Here, we focus on traditional diets of rural communities in sub-Saharan Africa to identify how Westernization of diet changes the intestinal milieu and affects gastrointestinal health. In collaborative research efforts together with local partners (e.g., African Microbiome Institute at Stellenbosch University, South Africa) and international research initiatives such as the German Alliance for Global Health Research (GLOHRA), we analyze dietary patterns and gut microbiota profiles from different healthy cohorts in rural sub-Saharan Africa. These clinical observation studies are complemented by mechanistic work in gnotobiotic animal models to study causal relationships in underlying interactions of diet, gut bacteria and the host. Current projects investigate the role of dietary fiber and short-chain fatty acid-producing bacteria in colorectal cancer risk, and the functional relevance of bile pigments and microbial bile acid metabolism in intestinal health.

Based on this multidisciplinary approach, we aim to identify how dietary factors may help to maintain gut health in populations of the Global South that are currently undergoing nutrition transition to a Western diet. In addition, we will also learn how dietary and environmental factors in rural sub-Saharan Africa shape a human gut microbiota that may be beneficial in terms of NCD prevention.

  1. Ocvirk, S. & O’Keefe, S. J. D.: Dietary fat, bile acid metabolism and colorectal cancer. Semin. Cancer Biol. 73, 347–355 (2021).

  2. Ocvirk, S., Wilson, A. S., Posma, J. M., Li, J. V., Koller, K. R., Day, G. M., Flanagan, C. A., Otto, J. E., Sacco, P. E., Sacco, F. D., Sapp, F. R., Wilson, A. S., Newton, K., Brouard, F., DeLany, J. P., Behnning, M., Appolonia, C. N., Soni, D., Bhatti, F., Methe, B., Fitch, A., Morris, A., Gaskins, H. R., Kinross, J., Nicholson, J. K., Thomas, T. K., O’Keefe, S. J. D.: A prospective cohort analysis of gut microbial co-metabolism in Alaska Native and rural African people at high and low risk of colorectal cancer. Am. J. Clin. Nutr. 111(2), 406–419 (2020).

  3. Katsidzira, L., Ocvirk, S., Wilson, A., Li, J., Mahachi, C. B., Soni, D., DeLany, J., Nicholson, J. K., Zoetendal, E. G., O’Keefe, S. J. D.: Differences in fecal gut microbiota, short-chain fatty acids and bile acids link colorectal cancer risk to dietary changes associated with urbanization among Zimbabweans. Nutr. Cancer. 71, 1313-1324 (2019).

  4. Ocvirk S., O’Keefe S. J. D.: Influence of Bile Acids on Colorectal Cancer Risk: Potential Mechanisms Mediated by Diet - Gut Microbiota Interactions. Curr. Nutr. Rep. 6(4), 315–22 (2017).