Secondary
outcomes include safety and tolerability
of vitamin D supplementation;
variation of response to vitamin D supplementation
among subgroups defined
by key baseline characteristics; variability
of response to vitamin D supplementation
by adherence based on pill counts
and by achieved 25OHD concentration;
effect of vitamin D supplementation on
hemoglobin A1c, FPG, and 2hPG as continuous
variables, insulin resistance and
secretion (indices derived from the
OGTT), systolic and diastolic blood pressure
and blood 25OHD concentration;
and identification of phenotypic, including
seasonal and geographic, characteristics
associated with variation in achieved
blood 25OHD concentration.