Bone mineral density in Nigerian children after discontinuation of calcium supplementation

Highlights

• Calcium supplementation increased areal bone density in Nigerian toddlers.

• Ground fish was an effective indigenous source of calcium supplementation.

• Increased areal bone density was not sustained after calcium supplement withdrawal.

Abstract

Background

Nigerian toddlers with low dietary calcium intakes increased forearm bone mineral density (BMD) after 18 months of calcium supplementation compared with placebo. However, it is not known if this bone mineral accretion is sustained after calcium supplement withdrawal. We therefore investigated the influence of prior calcium supplementation on forearm BMD 12 months after withdrawal of the supplement.

Methods

Nigerian toddlers aged 12–18 months from three urban communities were enrolled in a controlled trial of calcium supplementation. Two communities received daily calcium supplements, one as calcium carbonate (400 mg), and the other as ground fish (529 ± 109 mg), for a duration of 18 months, and all three communities received vitamin A (2500 IU daily) as placebo. Forearm BMD was measured 5 times during 18 months of calcium supplementation and at 12 months after supplement withdrawal.

Results

Of 647 children enrolled, 390 completed the trial of calcium supplementation and 261 of these returned for the final follow-up 12 months after discontinuation of supplementation. During the 18 months of supplementation, an adjusted model demonstrated that the increase in both distal and proximal forearm BMD over time was significantly greater in the calcium supplemented groups than in the placebo group (P < 0.04). However, after supplement withdrawal, the increase in BMD over time was largely attenuated and only remained significant at the proximal forearm in the ground fish group (P = 0.03).

Conclusion

The benefit of calcium supplementation on forearm BMD in young Nigerian children is not sustained after supplement withdrawal.

Introduction

Peak bone mass is achieved during the third decade of life, but 90% of this is accrued by the end of adolescence [1]. Low bone mass in children has been associated with both acute and long-term consequences. Achieving an optimal peak bone mass may reduce risk for osteoporosis and related fragility fractures later in life [2], [3]. Otherwise healthy African American and white pediatric patients with low bone mineral density have an increased incidence of forearm fractures [4], [5]. Insufficient dietary calcium has been associated with nutritional rickets in several tropical countries, including Nigeria [6]. Calcium has been used to successfully treat children with nutritional rickets in Nigeria [7].

Several double-blind, placebo-controlled studies have demonstrated that calcium supplementation for 1–3 years increases bone mass accrual in children ranging from age 6 to 14 years at baseline [8], [9], [10], [11], [12], [13]. These studies are supported by a meta-analysis of 19 randomized, controlled studies which demonstrated increased total body and arm bone mineral density associated with calcium supplementation regardless of sex, ethnicity, physical activity, or pubertal stage [14]. However, few of these studies examined the effects of dietary calcium supplementation in children with habitual low calcium intake [10], [12], [13]. Previously, we demonstrated that calcium supplementation in Nigerian toddlers age 12–18 months at baseline increased forearm areal bone mineral density (BMD) by 5–9% after 18 months compared with placebo [15].

Several studies have examined if the beneficial effects of calcium supplementation on bone mass are sustained after discontinuation, and the results are inconsistent [11], [16], [17], [18], [19], [20], [21]. None of these studies have examined the effects of discontinuation of calcium supplementation on BMD in children under the age of 5 years. Thus the objective of this study was to determine if the increased BMD in young Nigerian children following calcium supplementation is sustained 1 year after discontinuation of supplemental calcium.