Fiber may boost vitamin B availability in the gut and support immunity
Data published in Microbiome indicated that depriving lab mice of fiber in their diet led to a significant decrease in microbiota-produced B vitamins, which play a role in immune regulation. The lack of fiber caused some bacteria to use up the B vitamins for themselves, leaving less for the host.
However, additional experiments showed that supplementation with either complex fibers or prebiotic inulin restored the production of these vitamins and re-established immune balance.
“These data emphasize the multimodal role of dietary fiber to harness microbial synthesis of anti-inflammatory and immune-regulating metabolites and vitamins in the colon,” wrote scientists from the Luxembourg Institute of Health, led by Professor Mahesh Desai.
“While we highlight dynamics for B vitamins in this work, it is also clear that the synthesis of other microbial metabolites, such as secondary bile acids and the expected SCFAs [short chain fatty acids], are also altered in the face of fiber deprivation, collectively influencing local immunity.
“Assessing metabolic products from the fermentation of specific fiber types by specific bacterial species will be a useful intermediate step in translating this work to humans, along with mechanistic work in cell lines or mice to improve understanding of the associated host effects.”
Implications for personalization
In addition to deepening our understanding of the role of specific fibers in the gut, the study also highlights opportunities for approaches in using diet to modulate the microbiome and improve immune health.
“Regarding translational applications in humans,” said Dr. Amy Parrish, joint first author of the publication. “This could have significant implications for personalized nutrition and the development of targeted dietary interventions to support colonic immune health.”
Study details
Professor Desai and his co-workers fed lab mice one of five different types of diets: 1) a fiber-free diet; 2) a standard rodent chow; 3) rodent chow with added fiber from cereals, alfalfa, yeast and beet; 4) a fiber-free diet with additional inulin; or 5) the fiber-free diet fortified with fiber from apple, wheat, oat, pea and psyllium.
Results from this 40-day feeding study showed that fiber deprivation consistently led to a marked decrease in microbiota-produced B vitamins.
On the other hand, supplementation with either complex cereal fibers or inulin restored the production of these vitamins and re-established immune balance.
“This phenomenon was not always explained by reduced biosynthesis, rather, metatranscriptomic analyses pointed toward increased microbial usage of certain B vitamins under fiber-free conditions, ultimately resulting in a net reduction of host-available B vitamins,” wrote the researchers.
“Broad immunophenotyping indicated that the local gut effector immune populations and activated T cells accumulate in a microbiota-dependent manner.”
The data also showed that inulin supplementation led to a recovery in the availability of microbially-produced B vitamins and a restoration in immune balance.
Professor Mahesh Desai explained: “Our findings underscore the significant role of dietary fibers in modulating the gut bacteria's metabolic output, particularly in enhancing the availability of B vitamins. This, in turn, has a profound effect on the host's immune landscape. Since deficiency of B vitamins is associated with a plethora of diseases, our study highlights the potential for dietary interventions to boost B vitamins in the large intestine in order to support immune health.”
Probiota: Exploring the ‘pantryome’
The study has links to a wider conversation about a concept called the “pantryome”. Proposed by Dr. Jeremy Burton at the Lawson Health Research Institute, the pantryome is based on the idea of community sharing of nutritional metabolites produced by the microbiome. In other words, individual bacteria that lack some nutrients can access what they need from this shared pool of metabolites and can, in return, give excess metabolites back to the pool for other microorganisms to use.
This concept has important implications when thinking about health, wellness and disease as we need to think about the microbial community as a whole and not just an individual bacterium.
The topic will be explored at the upcoming Probiota in Copenhagen, Feb. 5-7, 2025, with presentations by Dr. Burton and Dr. Robert Steinert, principal scientist, health, nutrition & care, dsm-firmenich. For more information, please click HERE.
Source: Microbiome
2024, 12, 179. doi: 10.1186/s40168-024-01898-7
“Dietary fibers boost gut microbiota-produced B vitamin pool and alter host immune landscape”
Authors: E.T. Grant, et al.
