Vitamin D deficiency is a global epidemic and has been linked to many autoimmune diseases, including type 1 diabetes, systemic lupus erythematosus, multiple sclerosis, and inflammatory bowel disease (IBD). In a study just published this month, researchers investigated the impact of high dose vitamin D supplementation on the composition of the gut microbiome of adolescent girls.

Previous research has shown an interaction between the gut microbiome with vitamin D. Animal studies have shown that vitamin D can change the composition of the gut microbiome. This data suggests vitamin D may play a role in modulating the microbiome, and a deficiency may lead to inflammation or dysbiosis. Some human data demonstrates vitamin D may shift the microbiome in IBD.

This new research was an intervention study including 50 healthy teenage females between the ages of 12 and 18 years. All fifty individuals received vitamin D supplementation at 50,000 IU once a week over a nine-week period. Fasting vitamin D levels were assessed at baseline and at the end of the study, and stool samples were taken as well. At the start of the study 86% of the participants had a vitamin D deficiency (20 ng/ml or less), 8% had an insuffiency (21-29 ng/ml), and only 6% had normal levels (30 ng/ml or higher). The results showed that vitamin D supplementation significantly improved vitamin D status as well as increased levels of Firmicutes and Bifidobacterium. In addition, there was a reduction of Bacteroidetes after supplementation.

There are a few mechanisms in which vitamin D may have this effect. Its impact on the gut microbiome is most likely from immune modulation and well as anti-inflammatory effects, which change the microbiome composition.

Although this study used high weekly dosing of vitamin D, most patients will obtain optimal levels of vitamin D in daily doses between 5,000 IU and 10,000 IUs. Research suggests daily dosing is more effective than weekly dosing. It is also essential to use a supplement that combines vitamin D with vitamin K, or provide a separate vitamin K supplement. There are intricate relationships between fat-soluble vitamins and it is important take this into account when recommending vitamin D.

By Michael Jurgelewicz, DC, DACBN, DCBCN, CNS

Source: Tabatabaeozadeh SA, Fazeli M, et al. The effects of high doses of vitamin D on the composition of the gut microbiome of adolescent girls. Clin Nutr ESPEN. 2020 Feb;35:103-108.