Vitamin D Supplementation Alone Does Not Increase Bone Structure, Strength

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In older adults, no significant changes in bone strength or structure were noted after 2 years of daily vitamin D supplementation.

Daily vitamin D supplementation alone does not improve bone density or strength in older adults, according to study results published in the Journal of Bone and Mineral Research.

Vitamin D supplements are commonly prescribed to promote bone health and prevent osteoporosis. However, it is unclear whether vitamin D alone (without calcium) increases bone mass or improves bone structure. In the randomized placebo-controlled Vitamin D and Omega-3 Trial (VITAL; Identifier: NCT01747447, NCT01704859), researchers aimed to evaluate the effects of vitamin D supplementation on bone mineral density (BMD) and bone strength in a generally healthy population of older adults (men and women ≥50 and ≥55 years of age, respectively) not selected for vitamin D insufficiency.

A cohort of 771 individuals (46.7% women) who resided within driving distance of Boston, Massachusetts, received either 2000 IU/d of vitamin D3 (n=388) or placebo (n=383). Fasting blood samples were collected at baseline and at 2-year follow-up. Total vitamin D levels were measured by liquid chromatography tandem mass spectrometry and free vitamin D levels were measured by enzyme-linked immunosorbent assay (ELISA). Areal BMD at the lumbar spine, nondominant hip, and whole body were measured by dual-energy x-ray absorptiometry. Secondary endpoints included changes in bone structure and strength, assessed by peripheral quantitative computed tomography at follow-up.

At baseline, the mean serum total vitamin D level was 69.1 nmol/L in the treatment group. At follow-up, mean total vitamin D levels increased to 98.6 nmol/L (+46.2%). The mean free vitamin D level was 14.6 pmol/L at baseline, which increased to 22.3 pmol/L (+55.5%) at follow-up. Total vitamin D levels were similar in the control group at baseline (71.1 nmol/L) and follow-up (70.6 nmol/L).

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At year 2, changes in areal BMD at all sites were <1% in both the treatment and placebo groups, with no significant changes observed in bone mass or bone loss in either group. In addition, vitamin D supplementation had no observed effects on bone structure or strength. In subgroup analyses, small benefits were observed in patients with free vitamin D levels that were below the median (14.2 pmol/L) at baseline, including increased spine areal BMD (0.75% vs 0.0%; P =.043) and smaller decreases in total hip areal BMD (-0.42% vs -0.98%; P =.044) compared with the placebo control group.

The study researchers noted that the results were not adjusted for multiple hypothesis testing and that the findings from the secondary and subgroup analyses should be considered as exploratory. They also noted that the exclusion of young people and people with profound vitamin D deficiency limit the interpretation of results to groups who might otherwise benefit from treatment.

“In summary, this placebo-controlled [randomized controlled trial] found that daily vitamin D3 supplementation for 2 years did not improve bone density or structure in the general population of older adults in the US not selected for vitamin D insufficiency,” the researchers concluded.

Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of disclosures.

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LeBoff MS, Chou SH, Murata EM, et al. Effects of supplemental vitamin D on bone health outcomes in women and men in the vitamin D and omega-3 trial (VITAL) [published online January 10, 2020]. J Bone Miner Res. doi:10.1002/jbmr.3958

This article originally appeared on Endocrinology Advisor