Wild rice as a microbiome-mediated colorectal cancer-reducing amendment to the Western Diet

Abstract

Colorectal cancer (CRC) is increasing in frequency, especially in increasingly younger populations. This risk is elevated in rural and Indigenous populations across the US and within the state of Minnesota. The average diet of many Americans contains low fiber, highly refined carbohydrates, and red meats. These dietary patterns overlap significantly with dietary patterns associated with CRC. Dietary fiber is known for its chemopreventive and overall health-promoting properties. Addressing the diet by adding more dietary fiber is a potential way to reduce the risk of developing CRC. Wild rice is known to be a source of dietary fiber and beneficial antioxidants and nutrients. Additionally, wild rice is sacred and accessible to Indigenous communities, making it an attractive potential dietary amendment to also address the disparate health risks these groups face. Dietary fiber interventions from other rice varieties are known to have many benefits by influencing the composition of the gut microbiome, increasing beneficial metabolites like short-chain fatty acids (SCFAs), and ameliorating CRC outcomes. This study demonstrated that when wild rice was added to the diet of rats, abnormally growing cells in the colon were significantly less likely to display cancerous markers. SCFA concentrations within the cecum increased, which are known to have protective and antitumor properties within the gut. Wild rice also had effects on the gut microbial community, increasing alpha diversity indices and producing microbiome communities that were significantly different from those of rats on a diet without wild rice, showing one small dietary change had a significant impact. Beneficial SCFA-producing taxa such as the Lachnospiraceae and Ruminococcaceae families were influenced positively by wild rice in the diet. In culture-based methods, wild rice supplementation facilitated the growth of the probiotic bacteria Limosilactobacillus reuteri. Based on these results, wild rice as a source of dietary fiber has the potential to be a chemopreventive agent against CRC by influencing the types and presence of microorganisms and their metabolic products within the gut.