In a recent review published in the journal Food Research International, researchers reviewed the impact of vitamins C and E and β-carotene on the gut microbiome to understand how known vitamins modify the gut microbiota.
Background
A growing body of evidence indicates that the gut microbiome plays a significant role in human health and the development of various diseases. Diet can cause changes in the gut microbiome directly by altering the metabolic state and composition of the gut microbiome or indirectly by altering the intestinal environment. Furthermore, dietary intake is the least intrusive and most direct method to influence gut microbiome composition.
Apart from the macronutrient content of the diet, such as fats, carbohydrates, and proteins, the micronutrient intake, such as vitamins, can also alter the diversity and abundance of the gut microbiome.
Vitamins C and E and β-carotene have antioxidant properties and protect cellular components by blocking reactive free radicals. Vitamin C is also essential for the normal functioning of the central nervous system, while vitamin E is important for the protection of cellular membranes from free-radical damage.
Β-carotene is a common carotenoid, and along with vitamins C and E, it has shown beneficial effects in the treatment of various diseases such as type 2 diabetes, periodontal disease, non-alcoholic fatty liver disease, and Parkinson’s disease. Given their significant roles in human health, it is important to understand their impact on the gut microbiome.
Vitamin C and the gut microbiome
Vitamin C is water soluble and is important in hormone, collagen, and carnitine synthesis by promoting iron ion absorption. It also contributes to the functioning of the immune system. Various studies on animal models have shown that vitamin C improves immune health and digestion and inhibits the growth of bacteria. Supplementation of broiler feed with vitamin C increased the Firmicutes/Bacteriodetes ratio, improved gut health, and decreased Enterobacteriaceae abundance.
Hypertension is believed to be linked to gut microbiome dysbiosis. In mouse models of hypertension, supplementation with vitamin C improved the richness and diversity of the gut microbiome, reduced oxidative stress and inflammation, and lowered blood pressure. In vitro studies using a fermentation reactor found that treatment with vitamin C increased the abundance of Firmicutes, Actinobacteria, and Verrucomicrobia, and decreased the phylum level abundance of Bacteriodetes, while increasing the genus level relative abundance of Bifidobacterium, Faecalibacterium, Roseburia, and Akkermansia.
Impact of vitamin E on gut microbiota
Vitamin E is fat-soluble and mainly found in seeds, nuts, and edible oils. Of its eight isomers, α-tocopherol is the most common one. Vitamin E has been used in adjunctive and preventative therapy in Alzheimer’s disease, cardiovascular disease, and non-alcoholic fatty liver disease.
Interventional studies in humans have reported the potential impacts of vitamin E on the gut microbiome. Studies among lactating women and infants with iron deficiency indicated an increase in the abundance of Firmicutes after supplementation with vitamin E. The studies also reported a decrease in the abundance of Bacteriodetes. Another study comprising pregnant women showed a decrease in the relative abundance of the phylum Proteobacteria as compared to Firmicutes, and Actinobacteria after vitamin E supplementation.
Studies in animal models reported improvements in the abundance of Ruminococcaceae, Lachnospiraheae, and Roseburia after supplementation with tocopherols. In mouse models of colitis-associated colon cancer, diets supplemented with vitamin E significantly altered the β-diversity and composition of the gut microbiome. In vitro studies have also shown an increase in the abundance of Firmicutes, and Actinobacteria and decreased abundance of Bacteriodetes associated with vitamin E supplementation.
β-carotene and the gut microbiome
β-carotene is a source of vitamin A and is found in various vegetables and fruits. Studies have reported anti-cancer, antioxidant, cardioprotective, and immunomodulatory properties associated with β-carotene. Various longitudinal observation studies, some involving postpartum women, have reported positive associations between β-carotene supplementation and Firmicutes diversity and negative associations between the abundance of Bacteriodetes and β-carotene.
Animal studies reported that β-carotene supplementation resulted in increased α-diversity, modulations of the gut microbiome resulting in reduced inflammatory cytokine production, increased abundance of Candidatus, Akkermansia, Faecalibaculum, and Stoquefichus, and a lower relative abundance of Helicobacteraceae, Proteobacteria, Alloprevotella, Peptococcaceae, and Helicobacter.
Conclusions
Overall, the findings indicated that supplementation with vitamins C and E and β-carotene modulate the diversity and abundance of the gut microbiome, maintain immune system function, and improve intestinal barrier function. Various animal, human, and in vitro studies have reported that supplementation with vitamins C and E and β-carotene improve the Firmicutes/ Bacteriodetes ratio.
