Vitamin D has become a bit of a controversial topic lately. While there is a lot of recent promising research demonstrating effectiveness of vitamin D supplementation for many serious conditions, at the same time there has been a significant push by certain groups (both pharma-affiliated and in the general population) to discredit vitamin D by promoting the idea that it is some kind of a poison, even at physiological/therapeutic doses, based on the fact that extremely high (and toxic) amounts of vitamin D are used as rat poison. If one peruses the literature on PubMed about this topic, it becomes quickly apparent that cases of vitamin D-induced hypercalcemia (the mechanism through which rats are killed with vitamin D overdose) are very, very rare and amount to probably no more than a few hundred annually in a country with the population of US. Even then, the cases invariably describe absurd dosing regimens, often with the intent of suicide, and as such are not relevant to the clinical usage of vitamin D in doses with well-established safety.
Be that as it may, the study below presents some very interesting findings. Namely, that one of the most common ocular conditions – myopia – may not only be directly caused by vitamin D deficiency (widespread in the general population), but may also be treatable by vitamin D supplementation. The study used calcitriol as the active intervention, but the same effects should be achievable with cholecalciferol(vitamin D3), with the latter also running much lower risk of causing hypercalcemia. The treatment lasted 4 weeks and the human-equivalent dose converted from calcitriol into cholecalciferol was 160 IU / kg (bodyweight) daily. That means for most people a daily dose of 10,000 IU – 12,000 IU vitamin D3 should be able to replicate the study design and its findings. That dose is considered high but is on par with what doctors prescribe in cases of vitamin D deficiency (50,000 IU – 75,000 IU once weekly).
https://www.nature.com/articles/s41598-024-62131-x
“…The annual increase in myopia prevalence poses a significant economic and health challenge. Our study investigated the effect of calcitriol role in myopia by inducing the condition in guinea pigs through form deprivation for four weeks. Untargeted metabolomics methods were used to analyze the differences in metabolites in the vitreous body, and the expression of vitamin D receptor (VDR) in the retina was detected. Following form deprivation, the guinea pigs received intraperitoneal injections of calcitriol at different concentrations. We assessed myopia progression using diopter measurements and biometric analysis after four weeks. Results indicated that form deprivation led to a pronounced shift towards myopia, characterized by reduced choroidal and scleral thickness, disorganized collagen fibers, and decreased scleral collagen fiber diameter. Notably, a reduction in calcitriol expression in vitreous body, diminished vitamin D and calcitriol levels in the blood, and decreased VDR protein expression in retinal tissues were observed in myopic guinea pigs. Calcitriol administration effectively slowed myopia progression, preserved choroidal and scleral thickness, and prevented the reduction of scleral collagen fiber diameter. Our findings highlight a significant decrease in calcitriol and VDR expressions in myopic guinea pigs and demonstrate that exogenous calcitriol supplementation can halt myopia development, enhancing choroidal and scleral thickness and scleral collagen fiber diameter.”
“…Given the rising incidence of myopia, which now stands as a principal contributor to visual impairment globally, the quest for efficacious myopia control methods remains critical19. Although low-dose atropine has shown effectiveness, its application is limited by adverse effects and a rebound effect post-discontinuation20,21. Consequently, identifying new, safer, and more efficacious strategies for myopia management is crucial. Our study confirmed the role of calcitriol and VDR in the onset and progression of myopia. We have established that exogenous calcitriol supplementation notably curbs myopia progression and alleviates reductions in choroidal and scleral thickness as well as scleral diameter, these findings provide new insights into the development of new drugs for myopia.”
