DISCUSSION
Numerous studies have looked at vitamin D and quality of
life; however, these are often epidemiologic in nature and
provide correlations between vitamin D status and HRQL at
one time point. The use of vitamin D supplements for the
purpose of improving and/or mitigating the decline in HRQL
is not a well-studied field. Specifically, the use of quality-oflife
measures is not the primary end point for many investigations
of vitamin D supplementation. There is great
heterogeneity in study populations (healthy vs diseased);
type, dose, and duration of vitamin D; and quality-of-life
tools used (see Tables 1 and 2 and Figure 2). In addition,
poor study design and lack of control for confounding variables
(sunlight exposure and dietary intake) was widespread
(Table 3). It is not surprising that there were inconsistent
findings in terms of quality-of-life change in response to
vitamin D supplementation.
Differences in dosing and t