New study on connection between gut microbes and Vit D levels.
Conclusions: To our knowledge this is the first report of increased circulating 25-hydroxyvitamin D in response to oral probiotic supplementation.
What was special about the L. reuteri used in the Vit D study, is that is was encapsulated in a substance resembling resistant starch, so it was able to survive the stomach ans small intestine and actually grow in the large intestine. The company that makes this probiotic uses "silicon dioxide, mag*nesium stearate, microcrystalline cellu*lose (for even dispersal of cultures)" to encapsulate the live bacteria.
This same effect is seen by simply stirring potato starch into your yogurt or kefir. The microbes love RS so much, they attach themselves to it the second they come in contact.