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Greater 25-(OH)D levels reached with 25-(OH)D3 supplementation over cholecalciferol
Healthy adults randomly assigned 25-hydroxyvitamin D3 supplementation gained faster and greater increases in serum 25-hydroxyvitamin D levels vs. those assigned standard vitamin D3 supplementation, according to recent findings.
“Presumably owing to its ability to bypass carbon-25 hydroxylation in the liver and its relative affinity for the circulating vitamin D-binding protein, pharmacologic [25-(OH)D3] (calcefidiol) more rapidly and robustly raises serum [25-(OH)D] than parent [vitamin] D3,” Albert Shieh, MD, a fellow in the department of medicine at the University of California, Los Angeles, and colleagues wrote. “[25-(OH)D3] administration also suppresses [parathyroid hormone] secretion while [vitamin] D3 does not.”
Shieh and colleagues analyzed data from 35 healthy adults with vitamin D levels less than 20 ng/mL recruited from the University of California student body and patient population. Researchers randomly assigned participants to 60 µg vitamin D3 once daily (n = 16) or 20 µg 25-(OH)D3 once daily (n = 19) for 16 weeks. Participants returned at 4, 8 and 16 weeks to provide blood and urine samples; researchers measured total 25-(OH)D, free 25-(OH)D, total 1,25-dihydroxyvitamin D, calcium, intact parathyroid hormone and urinary calcium-creatinine excretion ratio.
At 16 weeks, researchers found that 25-(OH)D3 supplementation increased 25-(OH)D levels to a greater extent than vitamin D3 supplementation with mean increases of 25.5 ng/mL vs. 13.8 ng/mL, respectively (P = .008). Participants assigned to 25-(OH)D3 also saw a greater increase in free 25-(OH)D vs. those assigned standard vitamin D3 (mean increase of 6.9 ng/mL vs. 3.6 ng/mL; P = .03). Mean total 25-(OH)D level remained at less than 30 ng/mL in the vitamin D3 group at 16 weeks (mean 25-[OH] level, 29.6 ng/mL). Trends were consistent across racial groups.
In mixed-effects regression models, researchers found that both higher total and free 25-(OH)D levels were associated with declines in parathyroid hormone from the time of 25-(OH)D measurement to the next follow-up visit.
“More specifically, for every ng/mL increase in total [25-(OH)D], [parathyroid hormone] decreased by 0.8% over the ensuing 4 weeks (P = .01),” the researchers wrote. “Along the same lines, for every ng/mL increase in free [25-(OH)D], [parathyroid hormone] decreased by 2.5% over the ensuing 4 weeks (P = .04). Of note, [parathyroid hormone] did not decrease significantly over the course of the study with either supplementation regimen (P > .6 for all). However, [parathyroid hormone] was already relatively low at study baseline.”
The researchers noted that, for patients with osteoporosis, an approach that will raise 25-(OH)D levels to at least 30 ng/mL can quickly optimize any response to antiresorptive therapy.
“While one could argue that bolus [vitamin] D2 or D3 fills this role adequately, this approach has recently been called into question given its association with increased risk for falls,” the researchers wrote. “In this setting, daily [25-(OH)D3] may be advantageous to [vitamin] D3.” – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.