Overall Study Design
D2d is a multicenter, randomized (1:1),
double-masked, placebo-controlled,
parallel-group, primary prevention clinical
trial with two arms (oral daily vitamin
D vs. placebo) in participants at
high risk for diabetes (i.e., prediabetes)
who will be followed for incident diabetes
for 2–4 years after randomization.
D2d was designed entirely by the planning
group (the authors) with input
from an NIDDK-appointed external
evaluation committee and investigators
at each collaborating site. No pharmaceutical
manufacturers contributed to
the planning or design or will participate
in the conduct of D2d. Study pills
were purchased from an independent
nutritional supplement manufacturing
company that has no association with
any members of the D2d Research
Group.