Assessment of Vitamin D Supplementation and Immune Function

Hypothesis: Volunteers with vitamin D insufficiency (serum 25(OH)D 25-50 nmol/L) given intermediate or high dose vitamin D supplements (2,000 or 5,000 IU per day) will have increased production of anti-bacterial peptides and interleukin-1, decreased production of other pro-inflammatory cytokines, increased production of regulatory cytokines and an enhanced T- and B-cell response to a tetanus vaccine compared to vitamin D insufficient subjects given low dose vitamin D supplements (400 IU per day).