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.
METHODS: Three-month-old Sprague-Dawley male rats (n = 18) were randomized equally into 3 groups. Bilateral orchidectomy was performed on 2 groups. The sham group was subjected to similar surgical stress, but their testes were retained. One of the orchidectomized groups received intramuscular injection of 7 mg/kg testosterone enanthate suspended in peanut oil weekly and the other 2 groups received equivolume of peanut oil injection. After 8 weeks, the rats were sacrificed and their blood was collected for the analysis of the levels of inflammatory cytokines and testosterone.
RESULTS: Testosterone level was significantly lower in the untreated orchidectomized group compared to the sham group. Testosterone replacement significantly increased the level of testosterone in the orchidectomized rats compared to the sham and untreated orchidectomized rats. Interleukin-1 alpha (IL-1α), interleukin-1 beta (IL-1β), and tumor necrosis factor alpha (TNFα) showed an increasing trend in orchidectomized rats, albeit not statistically significant. Interleukin-6 (IL-6) level increased significantly in the orchidectomized group compared to the sham group. Testosterone replacement at the supraphysiological dose did not alter the level of inflammatory cytokines significantly in orchidectomized rats.
CONCLUSIONS: Testosterone deficiency can elicit a state of low-grade inflammation, shown by an increase in interleukin-6 level, but exogenous supraphysiological testosterone replacement does not suppress the inflammation.