Physical activity modifies the effect of calcium supplements on bone loss in perimenopausal and postmenopausal women: subgroup analysis of a randomized controlled trial
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We aimed to determine whether the effect of calcium supplements on bone metabolism is modified by physical activity (PA) through a subgroup analysis of an RCT. PA may be a favorable effect modifier of the association between calcium intake and bone loss in perimenopausal and postmenopausal women.
Physical exercise can potentially modify bone metabolism. Here we aimed to determine whether the effect of calcium supplements on bone metabolism is modified by physical activity (PA) through a subgroup analysis of a randomized, double-blind, placebo-controlled trial.
The trial was conducted over the course of 2 years, and participants were 450 healthy women between 50 and 75 years of age who were randomly assigned to three equally-sized (N = 150 each) groups (500 mg calcium, 250 mg calcium, and placebo). Levels of PA at baseline were evaluated by quantifying moderate (4 METs) and vigorous (6 METs) activities based on a 7-day activity recall, and the total MET-hours per week was calculated. Follow-up BMD examinations were conducted 2 years later. Two-year changes in BMD were compared between the intention-to-treat higher PA subgroup (≥ 10 MET-hours/week) and the lower PA subgroup (< 10 MET-hours/week).
Of the 450 participants, 418 underwent follow-up BMD measurements. Regarding the lower PA subgroup, spinal BMD in the 500 mg/day calcium supplement group decreased significantly less (− 0.029 g/cm2, P = 0.042) than in the placebo group (− 0.045 g/cm2), and femoral neck BMD in the 500 mg/day calcium supplement group decreased significantly less (− 0.027 g/cm2, P = 0.049) than in the placebo group (− 0.038 g/cm2). In contrast, changes in neither spinal nor femoral neck BMD significantly differed between the three treatment groups in the higher PA subgroup.
PA is a favorable effect modifier of the association between calcium intake and bone loss in perimenopausal and postmenopausal women with low calcium intake.
Clinical trials registry number
KeywordsBone density Calcium Postmenopause Physical activity Randomized controlled trial
Study design: KN. Acquisition of data: KN, RK, RO, and KK. Interpretation of data: KN, TS, KK, and YW. Drafting of the manuscript: KN. Critical revision of the manuscript for important intellectual content: KN, KK, and YW. Statistical analysis: KN.
This trial was supported in part by a Grant-in-Aid for Scientific Research (B) No.20390183 from the Japanese Ministry of Education, Culture, Sports, Science and Technology; a Grant-in-Aid for Advanced Research from the Niigata University of Health and Welfare (2008-2010); a grant from the Japan Dairy Association (2009, 2010); and a grant from the Daiwa Securities Health Foundation (2008).
Compliance with ethical standards
The study was conducted in accordance with the Declaration of Helsinki, written informed consent was obtained from all participants, and the study protocol was approved by the Ethics Committee of Niigata University School of Medicine.
Conflict of interest
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