DATA SOURCES: Systematic search of MEDLINE, EMBASE, CINAHL, and the Cochrane Register of Controlled Trials.
STUDY SELECTION: Randomized controlled trials testing IV vitamin C in critically ill patients.
DATA ABSTRACTION: Two independent reviewers abstracted patient characteristics, treatment details, and clinical outcomes.
DATA SYNTHESIS: Fifteen studies involving 2,490 patients were identified. Compared with placebo, IV vitamin C administration is associated with a trend toward reduced overall mortality (relative risk, 0.87; 95% CI, 0.75-1.00; p = 0.06; test for heterogeneity I2 = 6%). High-dose IV vitamin C was associated with a significant reduction in overall mortality (relative risk, 0.70; 95% CI, 0.52-0.96; p = 0.03), whereas low-dose IV vitamin C had no effect (relative risk, 0.94; 95% CI, 0.79-1.07; p = 0.46; test for subgroup differences, p = 0.14). IV vitamin C monotherapy was associated with a significant reduction in overall mortality (relative risk, 0.64; 95% CI, 0.49-0.83; p = 0.006), whereas there was no effect with IV vitamin C combined therapy. No trial reported an increase in adverse events related to IV vitamin C.
CONCLUSIONS: IV vitamin C administration appears safe and may be associated with a trend toward reduction in overall mortality. High-dose IV vitamin C monotherapy may be associated with improved overall mortality, and further randomized controlled trials are warranted.
OBJECTIVE: This review aims to assess the current evidence of the bone-sparing effects of vitamin C derived from cell, animal and human studies.
RESULTS: Cell studies showed that vitamin C was able to induce osteoblast and osteoclast formation. However, high-dose vitamin C might increase oxidative stress and subsequently lead to cell death. Vitamin C-deficient animals showed impaired bone health due to increased osteoclast formation and decreased bone formation. Vitamin C supplementation was able to prevent bone loss in several animal models of bone loss. Human studies generally showed a positive relationship between vitamin C and bone health, indicated by bone mineral density, fracture probability and bone turnover markers. Some studies suggested that the relationship between vitamin C and bone health could be U-shaped, more prominent in certain subgroups and different between dietary and supplemental form. However, most of the studies were observational, thus could not confirm causality. One clinical trial was performed, but it was not a randomized controlled trial, thus confounding factors could not be excluded.
CONCLUSION: vitamin C may exert beneficial effects on bone, but more rigorous studies and clinical trials should be performed to validate this claim.