Human microbiome as a source of folate modifiable by nutritional and non-nutritional factors

Hippocrates, in 400 years before our era, indicated that the intestines are central to human health and that “bad digestion is the root of all evil”. The microbiome influences immune status, protects against colonization by pathogenic microorganisms, performs metabolic and trophic functions, and participates in the synthesis of vitamin K, B1, B6, B12, and folic acid. Diet is a key factor in determining its composition. For many microbial strains, p-aminobenzoic acid is an indispensable substrate for the formation of folates. Bifidobacteria (HRB) strains in humans are mainly responsible for the synthesis of folates. Non-HRB strains that have the ability to synthesize folates include B. thermophilum and B. longum ssp. The only hitherto indicated factor that can affect the microbiota’s potential for folate synthesis is metformin, which improves glucose tolerance in people with type II diabetes. Metformin reduces the production of glucose in the liver by inhibiting gluconeogenesis and glycogenolysis, increases the sensitivity of tissues to insulin, and reduces the absorption of glucose. In order to thoroughly understand the ability of the microbiota to synthesize folic acid, it is necessary to conduct studies that include people with varying degrees of exposure to factors that may affect health, such as: poor dietary habits, smoking, low physical activity, diet-related diseases, or taking medications.