2. Definition of Vitamin D Deficiency
Optimal serum concentration of 25-hydroxyvitamin D considers
only bone health and was defined as the concentration
that maximally suppresses serum parathyroid hormone [15].
Most experts define vitaminDdeficiency as a calcidiol level of
30 ng/mL, and vitamin D intoxication is
considered if >150 ng/mL [16]. There are variations among
professional bodies regarding the cut-off values for insufficient
or deficient vitamin D level [17].
According to a report of the Institute ofMedicine (IOM),
vitamin D at doses of 600 IU/day is beneficial for the bones,
but it is not certain if higher doses could reduce the risk
of chronic diseases, including cancer and cardiovascular
pathology [17]. A threshold effect between vitamin D status
and cardiovascular risk was suggested [11]. Zittermann et al.
found a vitamin D level of 30–35ng/L as the best choice for
risk reduction in cardiovascular mortality