The effect of calcium and vitamin D supplementation on obesity in postmenopausal women: secondary analysis for a large-scale, placebo controlled, double-blind, 4-year longitudinal clinical trial

Abstract

Background: It is undetermined whether calcium supplementation has an effect on obesity or body composition in postmenopausal women. The purpose of the study is to detect the effect of calcium supplementation on indices of obesity and body composition.

Methods: This is a secondary analysis of data from a population-based, double-blind, placebo-controlled, randomized trial designed to determine the effects of calcium and vitamin D on osteoporotic fractures. The cohort included 1179 postmenopausal women who were randomly assigned into one of three groups: 1) supplemental calcium (1400 mg/d or 1500 mg/d) plus vitamin D placebo (Ca-only group); 2) supplemental calcium (1400 mg/d or 1500 mg/d) plus supplemental vitamin D3 (1100 IU/d) (Ca + D group); or, 3) two placebos (placebo group). After applying the exclusion criteria for this analysis, 870 subjects were included in this study. The primary outcomes for the present study were changes in body mass index, trunk fat, trunk lean, and percentage of trunk fat after calcium supplementation.

Results: Changes in trunk fat, trunk lean, and percentage of trunk fat were significantly different between the calcium intervention groups (Ca-only group or Ca + D group) and the placebo group during the trial (P < 0.05). The calcium intervention groups gained less trunk fat and maintained more trunk lean when compared to the placebo group. No significant difference was observed for body mass index between groups.

Conclusion: Calcium supplementation over four years has a beneficial effect on body composition in postmenopausal women.

Figure 1

Percentage changes (Mean ± SE) in body composition by group assignment over the 4 years. BMI: body mass index, TrF: trunk fat, TrL: trunk lean, PTrF: percentage of trunk fat. Δ: percentage change, equals (Follow-up - Baseline)/Baseline * 100. Ca-only: calcium group; Ca + D: calcium plus vitamin D group; Placebo: placebos group. At baseline (year 0): Placebo (n = 206), Ca-only (n = 328), Ca + D (n = 336); at year 1: Placebo (n = 191), Ca-only (n = 310), Ca + D (n = 310); at year 2: Placebo (n = 187), Ca-only (n = 300), Ca + D (n = 298); at year 3: Placebo (n = 189), Ca-only (n = 287), Ca + D (n = 296); at year 4: Placebo (n = 178), Ca-only (n = 274), Ca + D (n = 297). The P values were calculated by analysis of covariance (ANCOVA) at each follow-up measure (time point). A general linear model (GLM) was used with phenotype changes as dependent variables, treatment as an independent variable, age, season, and estrogen use (stepwise multiple regression P < 0.05) as covariates. The significant covariates in the model were as follows: at year 1: season; at year 2: age, season, and estrogen use; at years 3 and 4: age and estrogen use.

Figure 2

Percentage changes (Mean ± SE) in serum 25(OH)D by group assignment over the 4 years. The sample and the data analysis method are the same as Figure 1.