[Effect of ultraviolet irradiation through glass on the level of 25-hydroxy vitamin D and bone metabolism in rats].
Level 5 - mechanism / opinion, no new human data
Animal experimental study
What was done
Wistar rats were fed a vitamin D-deficient diet and randomized into three groups for 21 days: no ultraviolet B (UVB) exposure, direct UVB exposure (160 min/day), and indirect UVB exposure through glass (160 min/day). At 21 days post-exposure, bone mineral density (BMD) and serum levels of 25-hydroxyvitamin D [25-(OH)D], parathyroid hormone (PTH), osteocalcin (OC), bone alkaline phosphatase (BALP), and carboxyterminal cross-linked telopeptide of type I collagen (ICTP) were measured.
What was found
Compared with the no UVB exposure group, the indirect UVB group had significantly higher BMD (0.036 ± 0.002 vs. 0.029 ± 0.002 g/cm², p < 0.01) and significantly lower serum ICTP (0.181 ± 0.067 vs. 0.194 ± 0.066 µg/L, p < 0.01), with no significant differences in PTH, 25-(OH)D, BALP, or OC. Compared with direct UVB exposure, indirect UVB resulted in lower 25-(OH)D (28.67 ± 1.35 vs. 34.69 ± 4.30 nmol/L, p < 0.01), higher PTH (0.181 ± 0.067 vs. 0.109 ± 0.067 µg/L, p < 0.05), and higher OC (0.559 ± 0.067 vs. 0.278 ± 0.067 ng/mL, p < 0.05). There were no significant differences in BMD, BALP, or ICTP between indirect and direct UVB exposure groups.
Why it matters
The study suggests that UVB exposure filtered through glass can exert beneficial effects on bone mineral density and bone turnover markers in vitamin D-deficient rats despite failing to increase circulating 25-(OH)D concentrations.
Limits
This is an animal study conducted in vitamin D-deficient rodents, limiting direct translation to human physiology. The total sample size and number of rats per group are not reported in the abstract. Properties of the glass (thickness, transmission spectra) and specific radiation wavelengths were not detailed.
Cited by
- supports Standard window glass prevents the skin from producing vitamin D.