12 January - 20 June 2016

Vitamin D supplementation can improve gut microbiome richness

A study published in the European Journal of Nutrition conducted by researchers from the Medical University of Graz, Austria, suggests that high doses of vitamin D may increase the diversity of gut microbiota in the upper Gastrointestinal (GI) tract and reduce bacteria which may explain the effects of vitamin D on irritable bowel disease (IBD) and bacterial infections.

A study published in the European Journal of Nutrition conducted by researchers from the Medical University of Graz, Austria, suggests that high doses of vitamin D may increase the diversity of gut microbiota in the upper Gastrointestinal (GI) tract and reduce bacteria which may explain the effects of vitamin D on irritable bowel disease (IBD) and bacterial infections.

Many factors, including diet, are known to affect the composition of the intestinal microbiome and the study by Bashir et al. notes that impairment of gut homoeostasis has been linked to a number of gastrointestinal diseases including IBD, irritable bowel syndrome (IBS) and intestinal infections. Appropriate vitamin D levels have previously been shown to be associated with a lower risk of autoimmune diseases including IBD but the current study indicates that the effects of vitamin D on the intestinal microbiome have not previously been investigated. Bashir et al. hypothesised that some of the beneficial effects of vitamin D might be brought about by the intestinal microbiome.

The authors recruited seven female and nine male, non-smoking, volunteers aged between 18 and 40. These participants were examined by a gastroduodenoscopy and colonoscopy and samples were taken from seven sites across the stomach, small bowel and colon along with stool samples both before and after the trial. During the trial, participants were given vitamin D3 supplements of a daily average dose of 140 IU/kg bodyweight for four weeks to a maximum of 68,600 IU/week followed by an additional four weeks with an average daily dose of 70 IU/kg bodyweight to a maximum of 34,300 IU/week.

Bashir et al. discovered that after the 8-week vitamin D3 supplementation, there was an increase in microbiome diversity and a significant decrease in Gammaproteobacteria including “opportunistic pathogens” such as Pseudomonas spp. and Escherichia/Shigella spp, mainly in the upper GI tract. Only minor changes were found in the lower GI Tract and stool samples. The study found that “the intestinal microbiome varies along the human GI tract and thus supports a previous study which found a similar bacterial distribution pattern in the ileum and colon of healthy humans”. In addition, Bashir et al. “observed a trend towards elevated CD8+ T (immune) cell levels in all seven assessed GI regions,” and suggest that the increase in the fraction of CD8+T cells in the upper GI tract might be responsible for the decrease in Gammaproteobacteria. The study also notes that CD8+T cells are capable of “directly destroying harmed or infected host cells, thus lowering the number of pro-inflammatory cells” which might in turn diminish the advantage opportunistic pathogens have in an inflammatory environment.

Bashir et al. note[JM1]  that an increase in microbiome diversity “could be particularly beneficial for gastrointestinal problems such non-alcoholic steatohepatitis or IBD which is characterised by decreased bacterial richness, lower vitamin D levels, and an overgrowth of pathogens”. In conclusion, the authors reiterate that the reduction in Gammaproteobacteria and increased microbiome diversity “supports the beneficial effect of a high-dose vitD3 supplementation on the human gut microbiome” and might go some way to explaining the effects of vitamin D on IBD and gut bacterial infections. They also note that the fact that the effects were only evident in the upper GI tract should guide future microbiome work to also assess this area as well as stool and colonic samples.

RSSL's Functional Ingredients Laboratory provides vitamin analysis in a wide range of matrices including drinks, fortified foods, pre-mixes and multi-vitamin tablets, including the analysis for  Vitamin D2 and Vitamin D3.  For more information please contact Customer Services on +44 (0) 118 918 4076 or email enquiries@rssl.com

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