In a recent study published in PLoS Pathogensresearchers explore the role of the human gut microbiome as a source of essential vitamins.
Study: Can we microbially manage our vitamin intake for better health? Image Credit: Lallapie/Shutterstock.com
Production of vitamins by the intestinal microbiota
Vitamins are essential micronutrients required for various metabolic and regulatory processes in all living organisms. Importantly, many vitamins cannot be synthesized by humans; therefore, they must be obtained from external sources.
Within the gastrointestinal (GI) tract, many microorganisms can produce vitamins again, some of which include vitamin K and various B vitamins such as niacin, riboflavin and cobalamin. Indeed, recent genome annotation studies have indicated that up to 65% of human gut commensal microorganisms produce at least one type of vitamin B, with some organisms producing all eight and others not involved in again vitamin synthesis. The gut microbiota is also capable of converting dietary vitamin A into its metabolites, which subsequently contribute to immune homeostasis and protection against pathogenic invasion.
Recent estimates indicate that up to 30% of the recommended daily intake of these vitamins is produced by the intestinal microbiota. However, this largely depends on the individual’s dietary habits and microbiome composition.
Vitamins may also exert beneficial effects on the gut microbiota by increasing the number of commensal microorganisms, enhancing microbial diversity, modifying short-chain fatty acid (SCFA) levels, and regulating barrier function and immune response capabilities. Furthermore, vitamins exhibit antioxidant properties that can protect the host from infectious diseases by directly influencing the immune system or indirectly through their impact on the redox state.
The role of pathogens in the gastrointestinal tract
The presence of opportunistic pathogens such as candida albicans in the human gastrointestinal tract can lead to serious and life-threatening invasive disease. Notably, most individuals carry these pathogens in the gastrointestinal tract without experiencing any infection, thus indicating a potentially commensal role of these organisms.
There are various benefits that can be attributed to harboring potential pathogenic species in the gastrointestinal tract. For example, C. albicans has been shown to produce high concentrations of riboflavin; however, the reason for this overproduction remains unclear. Comparatively, other pathogens appear to stimulate neutrophil reactivity, thereby training the immune system to respond to invasive infections.
Probiotics and diet
As research has advanced our understanding of the important role of the microbiome in human health, probiotic foods and supplements have become increasingly popular. Probiotics typically include Lactobacilli, BifidobacteriaOR Saccharomyces species, all capable of producing vitamins again.
Certain dietary habits can also affect vitamin production. High-carbohydrate, low-fat diets, for example, have been linked to increased urinary excretion of riboflavin, thus indicating a potential increase in riboflavin secretion by the microbiota under these conditions.
Vitamin fortification and its impact on human health
The enrichment of food products with vitamins is an approach that has been used to improve the nutritional quality of foods, particularly in high-income countries where diets are often dominated by high-calorie, low-nutrient food products.
In addition to fortified foods, vitamin supplementation is another way people can ensure they are meeting their daily vitamin needs; however, the scientific evidence supporting the benefits of vitamin supplementation is unclear. For example, excessive intake of fat-soluble vitamins such as vitamins A, D, E and K can accumulate in adipose tissue, thus leading to adverse health effects.
Additionally, there is some research indicating that the high doses that are often used in oral vitamin supplements can disrupt host-microbiome interactions by altering the competitive or syntrophic interactions between gut microbes. For example, previous live Studies in mice have shown that supplementing with vitamin B12 promotes the colonization and pathogenesis of a specific mouse pathogen known as Citrobacter rodentium interfering with Lachnospiraceae activity.
The study results underscore the importance of the commensal relationship between the gut microbiota and the human host through its role as a source of critical vitamins. Further research is needed to elucidate the molecular mechanisms of communication between the microbiome and the human host to discern the impact of these microorganisms on human health and potentially identify new therapeutic targets.
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