This is a monocentric, open pilot study, with the aim to evaluate the effect of vitamin d supplementation on regulatory FoxP3+ T cells in the gastrointestinal mucosa in healthy women and men.~The primary goal is to evaluate the influence of vitamin D supplementation on the regulatory FoxP3+ T cells in the gastrointestinal mucosa under controlled conditions within 2 months.~The secondary study goals are to evaluate the effect of vitamin D supplementation on peripheral induced tregs and on other important immune cells in the tissue (NK, NKT cells and LPCD) and in the blood (NK, NKT cells, Th17, Th1, Th2 cells) within 2 months.
In this pilot study the investigators aim to investigate the effects of vitamin D supplementation on regulatory FoxP3+ T cells in the gastrointestinal mucosa in healthy women and men.