VITAL: No fracture risk reduction with supplemental vitamin D
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Vitamin D3 supplementation did not reduce fracture risk in a large cohort of U.S. adults not selected for vitamin D deficiency or osteoporosis, according to an ancillary analysis of the VITAL trial.
“In generally healthy women and men in the U.S., supplemental vitamin D3 was safe, but had no effect on fractures,” Meryl Susan LeBoff, MD, chief of the calcium and bone section in the endocrinology, diabetes and hypertension division at Brigham and Women’s Hospital and professor of medicine at Harvard Medical School, told Healio. “These findings are not generalizable to younger adults or those with vitamin D deficiency, low bone mass or osteoporosis.”
Vitamin D supplements are widely recommended and prescribed in the general population to promote bone health, but data on whether such supplements prevent fractures have been inconsistent, LeBoff said during a presentation at the American Society for Bone and Mineral Research annual meeting. An ancillary analysis of the VITAL trial aimed to assess whether supplemental vitamin D3 vs. placebo reduced risk for incident total, nonvertebral and hip fractures.
“Randomized controlled trials had been limited by bolus dosing, coadministration with calcium and small sample sizes,” LeBoff told Healio.
As Healio previously reported, VITAL was a randomized, double-blind, placebo-controlled trial assessing the effects of 2,000 IU supplemental vitamin D, with or without an omega-3 fatty acid supplement vs. placebo, in the primary prevention of cancer and cardiovascular disease in the United States. It included 25,871 healthy men and women across all 50 states, 20% African American, with no history of CVD or cancer (mean age, 67 years; mean BMI, 28.1 kg/m2; mean 25-hydroxyvitamin D level, 30.8 ng/mL). It had a hybrid design and was the largest randomized controlled trial for vitamin D, with a median 5.3-year duration. Study Participants provided blood samples and completed yearly questionnaires on medical history and falls. The main study findings, presented in November 2019, suggested the supplement failed to prevent major CV events and the development of invasive cancers over 5 years, although a deeper dive into the findings reveals a signal for benefits with vitamin D for certain subsets of patients.
In this ancillary study, LeBoff and colleagues assessed incident fractures that were self-reported on annual questionnaires and centrally adjudicated by detailed medical record review, using radiographs for hip or femur fractures. Researchers adjudicated 2,133 total fractures in the VITAL cohort and confirmed 1,991 fractures in 1,551 participants during the intervention period.
Researchers found supplemental vitamin D vs. placebo had no significant effect on incident total fractures (HR = 0.98; 95% CI, 0.89-1.08), nonvertebral fractures (HR = 0.97; 95% CI, 0.87-1.07) or hip fractures (HR = 1.01; 95% CI, 0.7-1.47), with results persisting after adjustments for age, sex and race. There was no effect modification by baseline age, sex, race, BMI or 25-(OH)D levels.
In sensitivity analyses, results did not change among participants adherent to study pill. Findings were similar in secondary analyses examining effects of vitamin D vs. placebo supplements on fractures excluding fingers, toes, skull and pathologic fractures and on major osteoporotic fractures.
“While we hypothesized a small effect of supplemental vitamin D on reducing fractures, in VITAL — the largest randomized controlled trial of supplemental vitamin D vs. placebo on incident fracture outcomes — we found no effect,” LeBoff said. “The participants who were enrolled from 50 U.S. states may have already reached the vitamin D level necessary for bone.”
A recent analysis, presented at ASBMR in 2019, found that supplemental vitamin D vs. placebo did not improve bone density or structure.
“These findings have important implications for public health guidelines on use of vitamin D supplements to reduce fractures in generally healthy, older women and men,” the researchers wrote in an abstract.
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LeBoff M, et al. Abstract 1034. Presented at: ASBMR Annual Meeting; Oct. 1-4, 2021; San Diego (hybrid meeting).
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