By Danny Kucharsky

MONTREAL — October 3, 2018 — Long-term, high-dose vitamin-D supplementation of 2,000 IU daily may have a slight beneficial effect on bone microarchitecture in seniors, according to results of a double-blind study presented at the 2018 Annual Meeting of the American Society for Bone and Mineral Research (ASBMR).

The trial evaluated the effect of 2-year long supplementation of 800 IU versus 2,000 IU daily of vitamin D on bone microarchitecture in patients aged 60 years or greater using high-resolution peripheral quantitative computed tomography (HR-pQCT).

HR-pQCT, a non-invasive imaging method, allows for in vivo 3-dimensional characterisation of human bone microstructure. Most trials use the 2-dimensional dual-energy x-ray absorptiometry (DXA) to assess bone outcomes, but DXA cannot resolve bone microstructure, explained lead author Ursina Meyer, PhD, Centre on Aging and Mobility, University Hospital Zurich, Zurich Switzerland, speaking here on September 28.

Dr. Meyer and colleagues recruited 273 patients undergoing unilateral total-knee replacement due to severe knee osteoarthritis. The team randomised patients to receive daily doses of either 2,000 IU vitamin D or the standard-dose of 800 IU vitamin D. All patients received 500 mg of calcium supplements daily.

After 2 years, the group receiving 2,000 IU vitamin D daily had higher 25(OH)D levels compared with the group receiving 800 IU vitamin D (35.7±6.8 vs 28.8±6.1 ng/ml; P≤ .001).

DXA showed similar small increases in mean areal bone mineral density (aBMD) at 2 years, but when investigators used HR-pQCT to assess bone outcomes at the tibia, there was a significant increase in trabecular number (TbN) (beta = 0.05mm-1 [95% confidence interval: 0.004 to 0.09]) at the tibia in the 2,000 IU group compared to the 800 IU vitamin D group. The increase in TbN was accompanied by a statistically trending lower rate of TbN bone loss in the 2,000 IU group.

The investigators observed no other statistically significant differences in other microstructural parameters of the tibia and radius.

In a preliminary subanalysis, a higher 2-year dose of vitamin D did not translate into increases in bone strength as represented by changes in stiffness or failure load compared with the 800 IU vitamin D group.

[Presentation title: Effect of High-Dose Vitamin D on Bone Microarchitecture assessed via High Resolution Peripheral Quantitative Computed Tomography (HR-pQCT): a Double-Blind RCT. Abstract FRI-0827]