There is controversy over whether African Americans have higher vitamin D requirements than recommended by the Institute of Medicine. We previously reported that maintaining serum 25(OH)D above 30 ng/mL does not prevent age-related bone loss. Herein, we report that bone strength is also unaffected by maintaining this level in this population. INTRODUCTION The role of vitamin D in bone strength has not been investigated in the African American (AA) population. METHODS A 3-year randomized controlled trial was designed to examine the effect of vitamin D supplementation on physical performance, bone loss, and bone strength in healthy older AA women. A total of 260 postmenopausal AA women, ages ≥ 60 years were randomized to a vitamin D3 or placebo arm. Vitamin D3 dose was adjusted to maintain serum 25OHD > 30 ng/mL. Bone mineral density, femoral axis length, and femoral neck (FN) width were measured by dual-energy X-ray absorptiometry. Composite indices of FN strength [compression strength index (CSI), bending strength index (BSI), and impact strength index (ISI)] were computed. RESULTS The mean age of participants was 68.2 ± 4.9 years. Baseline characteristics between groups were similar. The average dose of vitamin D3 was 3490 ± 1465 IU/day in the active group. The mean serum 25OHD was 46.8 ± 1.2 ng/mL versus 20.7 ± 1.1 ng/mL in the active versus placebo group. Serum 25OHD did not correlate with any composite indices. The longitudinal differences observed in FN width, CSI, BSI, and ISI in both groups were not statistically significant (all p values > 0.05). Further, there was no group × time interaction effect for any of the composite indices (all p values > 0.05). CONCLUSION Maintaining serum 25OHD > 30 ng/mL (75 nmol/L) does not affect bone strength in older AA women. There is no evidence to support vitamin D intake greater than the recommended RDA by the Institute of Medicine in this population for bone strength.

中文翻译：

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维生素D对老年非裔美国人骨骼强度的影响：一项随机对照试验。

非洲裔美国人是否对维生素D的需求是否高于医学研究所的建议，存在争议。我们先前曾报道保持血清25（OH）D高于30 ng / mL不能预防与年龄有关的骨质流失。在本文中，我们报告说，在该人群中维持这一水平也不会影响骨骼强度。引言尚未在非裔美国人（AA）人群中研究维生素D在骨骼强度中的作用。方法设计了一项为期3年的随机对照试验，以研究补充维生素D对健康的老年AA妇女的身体机能，骨骼损失和骨骼强度的影响。总共260名年龄≥60岁的绝经后AA妇女被随机分配至维生素D3或安慰剂组。调整维生素D3剂量以维持血清25OHD> 30 ng / mL。骨密度，通过双能X射线吸收法测量股骨轴长度和股骨颈（FN）宽度。计算FN强度的复合指数[压缩强度指数（CSI），弯曲强度指数（BSI）和冲击强度指数（ISI）]。结果参与者的平均年龄为68.2±4.9岁。组之间的基线特征相似。在活动组中，维生素D3的平均剂量为3490±1465 IU /天。活性组与安慰剂组的平均血清25OHD分别为46.8±1.2 ng / mL和20.7±1.1 ng / mL。血清25OHD与任何综合指数均不相关。两组的FN宽度，CSI，BSI和ISI的纵向差异均无统计学意义（所有p值> 0.05）。此外，对于任何复合指数（所有p值> 0.05），都没有组×时间相互作用的影响。结论维持血清25OHD> 30 ng / mL（75 nmol / L）不会影响老年AA妇女的骨强度。没有证据表明该人群中维生素D的摄入量超过医学研究所推荐的RDA。