Serious adverse events attributable to vitamin D supplementation were rare across all studies .
On the basis of studies review ed to date , the strongest evidence supports further research into adjunctive vitamin D therapy for tuberculosis , influenza , and viral upper respiratory tract illnesses .
OBJECTIVE To review the existing human controlled intervention studies of vitamin D as adjunctive therapy in setting s of infection and provide recommendations for design and implementation of future studies in this field on the basis of the evidence review ed .
A placebo-controlled trial to evaluate immunomodulatory effects of paricalcitol.
Calcitriol has shown a benefit in various small uncontrolled studies of ex vivo immune function . We hypothesized that paricalcitol , a new vitamin D derivative , will have a positive effect on the immune system with minimal adverse effects on calcium homeostasis . Thirty-one hemodialysis patients not administered vitamin D because of low intact parathyroid hormone ( PTH ) levels were r and omized to placebo or 4 microg of paricalcitol intravenously with the hemodialysis session three times weekly for 12 weeks . Effects on in vivo and ex vivo assessment s of immune function were evaluated . All patients achieved the target dose of paricalcitol .  Twenty patients were anergic at the start of the study ; 4 of 11 patients in the paricalcitol group and 0 of 9 patients in the placebo group converted to reactive ( P = 0.09 ) . The in vivo response to st and ard hepatitis B booster vaccine and in vitro proliferation and release of interleukin-2 ( IL-2 ) , IL-6 , tumor necrosis factor-alpha , and interferon-gamma from stimulated lymphocytes were not different between the groups . In contrast to clinical immune effects , paricalcitol increased serum calcium levels and decreased PTH and bone alkaline phosphatase levels ( all P < 0.05 ) . However , hypercalcemia was infrequent . In vitro experiments showed that paricalcitol led to greater dose-dependent thymidine uptake than calcitriol in lymphocytes isolated from either dialysis patients or control subjects . Paricalcitol has a tendency toward improving delayed hypersensitivity reactions , but did not have other proimmune effects . However , as expected , paricalcitol had significant effects on calcium homeostasis compared with placebo . Thus , patients with low PTH levels are unlikely to experience the proimmune effects of vitamin D therapy without more profound and potentially adverse oversuppression of PTH
Serious adverse events attributable to vitamin D supplementation were rare across all studies .
On the basis of studies review ed to date , the strongest evidence supports further research into adjunctive vitamin D therapy for tuberculosis , influenza , and viral upper respiratory tract illnesses .
OBJECTIVE To review the existing human controlled intervention studies of vitamin D as adjunctive therapy in setting s of infection and provide recommendations for design and implementation of future studies in this field on the basis of the evidence review ed .