The B vitamins are a class of water-soluble nutrients that have numerous important roles in everyday physiology and benefits to our health.

For example, the family of B vitamins plays a functional role in cellular energy production, as methyl donors for proper methylation, for neurotransmitter synthesis, in immune function, for cell signaling, and in DNA synthesis.

More recently, however, evidence is emerging that the B vitamins influence the composition and function of the gut microbiome.

How B vitamins shape the microbiome

Although the gut microbiome is complex, we know the major influences on this ecosystem generally take place in two ways:

  1. Directly ‒ the action of nutrients modulates its composition and activity. 
  2. Indirectly ‒ changes in gut physiology lead to changes in the ecosystem’s composition

The B vitamins play a crucial role in shaping the diversity and richness of the gut microbiota.1 Research is expanding on the role all vitamins play, not just the B vitamin complex, in directly influencing the microbiome, whether in sufficient, sub-optimal, or deficient amounts. 

At the same time, the gut contains bacteria that can directly make or support the pathways to produce the B vitamins. In turn, this production contributes to the B vitamin levels our bodies need daily for cellular processes and to support the microbiome ecosystem.2  

Each of the B vitamins plays a specific, bi-directional role in influencing the ecosystem of the gut microbiome, stressing the importance of maintaining a healthy gut for optimal B vitamin synthesis and function. 

The B vitamins and their roles in the microbiome

The following are several key things to know about each B vitamin:

Thiamin (vitamin B1) is synthesized by several bacteria in the gut, primarily by Prevotella and Desufovibrio, but almost 90 percent of Bacteroides can biosynthesize thiamin, too.3 Although the role of thiamine on intestinal integrity is not fully understood, some research suggests that thiamine directs the energy balance that controls immunometabolism and plays a role with intestinal-linked immune cells.4

Riboflavin (vitamin B2) is primarily produced by gut microbiota in the large intestine. Bacteroidetes and Fusobacteria, as well as 92 percent of Proteobacteria and 50 percent of Firmicutes, have the genetic capability to produce riboflavin.5 Riboflavin is also required in newborn nutrition, supplied from breast milk or formula, because it is needed for the early development of the GI tract.

Vitamin B3 in dietary supplements generally refers to two different molecules – niacin (nicotinic acid) and niacinamide (nicotinamide). Vitamin B3 is synthesized by intestinal bacteria from tryptophan. Several species of Bacilli, Clostridia, and Proteobacteria are niacin-synthesizing. In addition, Bacteroides fragilis, Prevotella copri, and Ruminococcus lactaris can also produce vitamin B3 in the gut.5 The special B3-synthesizing bacteria help maintain the morphology of intestinal stem cells and contribute to the nutrition of the epithelial cells that line the colon.6 Research shows associations between low vitamin B3 status and low gut microbiome alpha-diversity and abundance of Bacteroidetes in obese adults.7

Vitamin B5 or pantothenic acid is produced in the gut by the following bacterial species: Escherichia coli, Salmonella typhimurium, and Corynebacterium glutamicum. Research shows pantothenic acid supports the growth of Lactobacillus helveticus, which in turn is related to the synthesis of fatty acids used for producing cellular energy.8

Vitamin B6 is produced by multiple microbes in the gut, including Bacteroides fragilis and Prevotella copri (Bacteroidetes), Bifidobacterium longum and Collinsella aerofaciens (Actinobacteria), and Helicobacter pylori (Proteobacteria).9 A small study found low dietary intake of vitamin B6 was associated with greater gastrointestinal distress, perhaps explained by the role vitamin B6 plays in supporting a healthy balance of anti-inflammatory and pro-inflammatory cytokines.10

Biotin (vitamin B7) is produced by Bacteroides fragilis, Prevotella copri, Fusobacterium varium, and Campylobacter coli, and at the same time, Lactobacillus murinus is known to deplete biotin in the gut.11

Folate (vitamin B9) can be produced by many organisms that reside in the gut, including Bacteroides fragilis, Prevotella copri, Clostridium difficile, Lactobacillus Plantarum, L. reuteri, L. delbrueckii ssp. bulgaricus, Streptococcus thermophilus, Bifidobacterium spp., Fusobacterium varium, and Salmonella enterica.5 Some research indicates that a folate deficiency can alter intestinal cell structure and function.

Vitamin B12, or cobalamin, is perhaps the most complex B vitamin. Although it is made by 20 percent of the bacteria in the gut, it is needed by 80 percent of gut organisms for their metabolic reactions. A vitamin B12 deficiency can unfavorably impact changes in the intestinal barrier and the villus that line the GI tract. Vitamin B12 supplementation has been shown to increase Prevotella but decrease Bacteroides.12 

Why you should supplement your gut health with B vitamins

It has been long known that the biggest factors adversely affecting B vitamins in the gut include antibiotic use, free radicals, diet, and a person’s genetics.1 Because an individual’s B vitamin status can affect their gut microbial composition, colonic health, and overall metabolism, the overall ability to produce B vitamins should be considered when calculating B vitamin requirements for optimal health and wellness.

Want to learn about your gut’s ability to produce B vitamins? Thorne’s Gut Health Test provides insights into how well your gut is populated with the bacteria and pathways that produce B vitamins.

References

  1. Hossain KS, Amarasena S, Mayengbam S. B vitamins and their roles in gut health. Microorganisms 2022;10(6). doi:10.3390/microorganisms10061168
  2. Uebanso T, Shimohata T, Mawatari K, Takahashi A. Functional roles of B vitamins in the gut and gut microbiome. Mol Nutr Food Res 2020;64(18):e2000426.
  3. Costliow ZA, Degnan PH. Thiamine acquisition strategies impact metabolism and competition in the gut microbe Bacteroides thetaiotaomicron. mSystems 2017;2(5). doi:10.1128/mSystems.00116-17
  4. Mathis D, Shoelson SE. Immunometabolism: an emerging frontier. Nat Rev Immunol 2011;11(2):81.
  5. Magnúsdóttir S, Ravcheev D, de Crécy-Lagard V, Thiele I. Systematic genome assessment of B-vitamin biosynthesis suggests cooperation among gut microbes. Front Genet 2015;6:148.
  6. Kumar JS, Subramanian VS, Kapadia R, et al. Mammalian colonocytes possess a carrier-mediated mechanism for uptake of vitamin B3 (niacin): studies utilizing human and mouse colonic preparations. Am J Physiol Gastrointest Liver Physiol 2013;305(3):G207-G213.
  7. Fangmann D, Theismann EM, Türk K, et al. Targeted microbiome intervention by microencapsulated delayed-release niacin beneficially affects insulin sensitivity in humans. Diabetes Care 2018;41(3):398-405.
  8. Yao C, Chou J, Wang T, et al. Pantothenic acid, vitamin C, and biotin play important roles in the growth of Lactobacillus helveticus. Front Microbiol 2018;9:1194.
  9. Yoshii K, Hosomi K, Sawane K, Kunisawa J. Metabolism of dietary and microbial vitamin B family in the regulation of host immunity. Front Nutr 2019;6:48.
  10. Ligaarden SC, Farup PG. Low intake of vitamin B6 . . . . Nutr Res 2011;31(5):356-361.
  11. Hayashi A, Mikami Y, Miyamoto K, et al. Intestinal dysbiosis and biotin deprivation induce alopecia through overgrowth of Lactobacillus murinus in mice. Cell Rep 2017;20(7):1513-1524.
  12. Carrothers JM, York MA, Brooker SL, et al. Fecal microbial community structure is stable over time and related to variation in macronutrient and micronutrient intakes in lactating women. J Nutr 2015;145(10):2379-2388.