To the Editor A recent meta-analysis1 showed no significant association of calcium or vitamin D with risk of fractures, regardless of calcium dose, dietary calcium intake, or baseline serum 25(OH)D concentration. Vitamin D deficiency or insufficiency develops slowly, and it also takes time to optimize and maintain serum 25(OH)D concentration via supplementation. In the included RCTs, calcium and vitamin D supplementation lasted for 4 months to 7 years. This large variation in the treatment course might affect the results. Therefore, subgroup analyses based on calcium or vitamin D treatment course would be helpful. Other factors that might be investigated in subgroup analyses include baseline serum 25(OH)D concentration (as low as 10.6 ng/mL in the included RCTs), posttreatment serum 25(OH)D concentration, or change in 25(OH)D concentration.2,3 Posttreatment vitamin D level is also affected by various other factors,4 including body mass index, genetic background, or dose, route, and duration of vitamin D supplementation, which could influence the association of calcium or vitamin D with risk of fractures.
Wang Y, Huang Z, Yi B. Calcium and Vitamin D Supplements and Fractures in Community-Dwelling Adults. JAMA. 2018;319(19):2042. doi:10.1001/jama.2018.3919
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