GI

Vitamin D Supplementation Positively Impacts GI Diseases?

It is well known that vitamin D positively influences human health, but data on its impact on the human gut microbiome are lacking. Researchers conducted a pilot study on sixteen healthy volunteers. They were endoscopically examined to access a total of 7 sites to investigate the effects of oral vitamin D3 supplementation on the human mucosa-associated and stool microbiome, as well as CD8(+) T cells. Supplementation decreased relative abundance of Gammaproteobacteria including Pseudomonas spp. and Escherichia/Shigella spp. and increased bacterial richness. While no major changes occurred in the terminal ileum, appendiceal orifice, ascending colon, and sigmoid colon or in stools, the CD8(+) T cell fraction was significantly increased in the terminal ileum. Researchers concluded vitamin D3 modulates the gut microbiome of the upper GI tract, which might explain its positive influence on GI diseases such as inflammatory bowel disease or bacterial infections, and local effects of vitamin D demonstrate pronounced regional differences in the response of the GI microbiome to external factors.

Bashir M, et al. Effects of high djoses of vitamin D3 on mucosa-associated gut microbiome vary between regions of the human gastrointestinal tract. Eur J Nutr. 2016;55(4): 1479-89. doi: 10.1007/s00394-015-0966-2. Epub 2015 Jul 1.

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Gluten-Free Diet Impacts the Human Microbiome:

A gluten-free diet (GFD) is commonly adopted as an effective treatment for celiac disease, and is often followed to alleviate GI complaints. While we know there is an important link between diet and the gut microbiome, how a switch to a GFD affect the human gut microbiome is largely unknown. Twenty one healthy human volunteers followed a GFD for four weeks. Researchers collected stool samples from each at baseline, four during the GFD period, and four when they returned to their habitual diet (HD). They determined microbiome profiles using 16S rRNA sequencing, then processed the samples for taxonomic and imputed functional composition. They also measured six gut health-related biomarkers in all samples. Inter-individual variation in the gut microbiota remained stable during the short term GFD intervention. A number of taxon-specific differences were seen during the GDF: the most striking shift was seen for the family Veillonellaceae (class Clostridia), which was significantly reduced during the intervention. Seven other taxa also showed significant changes; the majority of them known to play a role in starch metabolism. Stronger differences in pathway activities were seen: 21 predicted pathway activity scores showed significant association to the diet change. Strong relation between the predicted activity of pathways and biomarker measurements were observed. Researchers concluded that CFD changes the gut microbiome composition and alters the activity of microbial pathways.

Bonder MJ, et al. The influence of a short-term gluten-free diet on the human gut microbiome. Genome Med. 2016 Apr 21;8(1):45. doi: 10.1186/s13073-016-0295-y.

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Vitamin D for gut microbiome and GI function?

Vitamin D is known for its effects on bone mineralization, inflammatory processes and immunomodulatory properties, which positively influences human health, but in-vivo data on its effects on human gut microbiome are missing. Researchers conducted an open-label, interventional pilot study to investigate the effects of oral vitamin D3 on the human mucosa-associated and stool microbiome as well as CD8+ T cells in healthy volunteers. Sixteen participants were endoscopically examined to access a total of 7 sites, and researchers sampled stomach, small bowel, colon, and stools before and after 8 weeks of vitamin D3 supplementation. Weeks 1-4 participants took a weekly dose representing 140 IU/Kg body weight per day up to a max of 68,600 IU/week (9,800 IU/day). The following 4 weeks they took half the amount (70 IU/Kg body weight per day up to 34,300 IU/week (4,900 IU/day). Supplementation changed the gut microbiome in the upper GI tract (gastric corpus, antrum and duodenum). Researchers found a decreased relative abundance of Gammaproteobacteria including Pseudomonas spp., Escherichia/Shigella spp. and increased bacterial richness. No major changes occurred in the terminal ileum, appendiceal orifice, ascending colon, and sigmoid colon or in stool, but the CD8+ T cell fraction was significantly increased in the terminal ileum. They concluded that vitamin D3 modulates the gut microbiome of the upper GI tract which might explain its positive influence on GI diseases such as inflammatory bowel disease or bacterial infections. Local effects demonstrate pronounce regional differences in the response of the GI microbiome to external factors.

M Bashir, et al. Effects of high doses of vitamin D3 on mucosa-associated gut microbiome vary between regions of the human gastrointestinal tract. Eur J Nutr. 2015 Jul 1. [Epub ahead of print]

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