Table 3.

Table of possible effects of vitamin D supplementation in patients with kidney disease

Outcome	Nutritional or Active Vitamin D	Proposed Mechanism	Level of Evidence	References
PTH suppression	A, maybe N	Direct suppression of parathyroid gland	A: RCT	13,14
			N: limited RCTs	15,66
Reduction of albuminuria	A, maybe N	Suppression of renin-angiotensin system	A: RCT	59
			N: limited RCTs	61
Reduced risk of infections	N	Increase in cathelicidin levels	Observational studies in general population only	32,33
Reduction of BP	A, maybe N	Suppression of renin-angiotensin system	A: RCT	59
Progression of kidney disease	A, maybe N	Suppression of renin-angiotensin system	A: Observational studies only	51,52
			N: low levels associated with outcome	38,46
Cardiovascular effects (left ventricular hypertrophy and vascular calcification)	A	Suppression of renin-angiotensin system, possibly direct effects on myocytes	Animal studies	20
Mortality	A	Likely multiple mechanisms	Observational studies only	6,7,48

PTH, parathyroid hormone; A, active; N, nutritional; RCT, randomized controlled trial.