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By Elaine S. Krul, PhD,
Gut microbiota play a critical role in human metabolism and health by processing nutrients and drugs, synthesizing vitamins and inhibiting growth of potential pathogen. The gut microbiota co-evolved with humans in a symbiotic manner, so that those microbes that thrive on ingredients in the human diet serve to provide additional metabolic activity to the host (gut microbiota have 100 times more genes than human), thereby enhancing nutrient availability while also affording protection against opportunistic pathogens. The large intestine harbors most of the gut microbiota and is the major site for fermentation of dietary ingredients which are not efficiently digested in the small intestine. The efficient extraction of energy from the diet made possible by the metabolic activity of the colonic microbiota, in some cases, has undesirable consequences. For instance, gut microbiota have a causal role in the development of obesity in mice. Ridaura et al. demonstrated that when gut microbiota from human twins who were discordant for obesity were transferred to germ-free mice, the mice receiving the microbiota from the obese twin had significantly more body mass and fat tissue than mice receiving the microbiota from the lean twin. The donor obese individuals had a higher ratio of certain phyla of bacteria (Firmicutes to Bacteroidetes) and overall reduced bacterial diversity in the gut compared with lean individuals.
By Mark Messina, PhD, MS,
Fermented soyfoods play an important role in the cuisines of many Asian countries. Fermentation produces changes in the composition of the food itself but the health implications of these changes aren’t precisely understood. Limited evidence suggests fermented soyfoods exert favorable changes on the composition of the intestinal microbiota.