Figure 1.

Schematic representation of the beneficial functions of the gut microbiota. Intrinsic and extrinsic factors can alter the composition of the gut microbiota, including the mode of delivery at birth, host genetics, age, antibiotics, exercise, dietary habit, and stress. The gut microbiota plays a critical role in human health, such as preservation of intestinal barrier integrity, breaking down food compounds (e.g., carbohydrates and proteins), supplying essential nutrients, and regulation of immune system development. Commensal microbes also coordinate energy, glucose and lipid metabolism. Importantly, they confer protection against invading pathogens. In addition, intestinal microbes have the ability to influence the bioavailability, absorption and therapeutic efficacy of oral agents.