Calcium Supplementation in Postmenopausal Women to Reduce the Risk of Osteoporotic Fractures

Mikayla Spangler, Pharm.D., BCPS; Beth Bryles Phillips, Pharm.D., FCCP, BCPS; Mary B. Ross, M.B.A.; Kevin G. Moores, Pharm.D.

Disclosures

Am J Health Syst Pharm. 2011;68(4):309-318. 

In This Article

Abstract and Introduction

Abstract

Purpose. The most recent large-scale studies evaluating the effects of calcium supplementation for prevention of osteoporosis-related fractures in postmenopausal women are reviewed.
Summary. Osteoporosis is a very common disease associated with significant morbidity and mortality. For many years, use of a calcium supplement (preferably in combination with vitamin D to optimize calcium absorption) has been recommended for postmenopausal women to decrease fracture risk. However, five large-scale, randomized, controlled trials have called into question the benefits of calcium in reducing fracture risk, and four of the studies indicated that calcium users may be at increased risk for renal stones and gastrointestinal problems. However, all five studies had one or more important limitations, including possible selection bias and study participants' relatively high baseline calcium intake and generally low adherence to treatment regimens. Moreover, in some of the studies, vitamin D was not included in the treatment protocol or was not used at levels sufficient to optimize calcium absorption. In three of the five trials, subgroup analysis of the most treatment-adherent participants indicated significant reductions in osteoporotic fracture risk with calcium supplement use.
Conclusion. Results of recent clinical trials indicate that calcium supplementation does not significantly reduce fracture risk in postmenopausal women. However, evidence from the same studies suggests that beneficial effects on fracture risk may be seen in women who are adherent to therapy. Postmenopausal women should continue calcium supplementation to reduce osteoporosis risk.

Introduction

Osteoporosis is a common disorder associated with significant morbidity and mortality and reduced quality of life. It is a devastating disease that underlies more than 1.5 million fractures in the United States each year,[1] resulting in an estimated $16.9 billion in medical costs.[2] Osteoporotic fractures are expected to increase by an alarming 48%, to 3 million, by the year 2025;[2] associated costs will exceed $25 billion. In addition, osteoporosis-related morbidity is high, with only 25% of patients regaining their previous level of functioning after an osteoporotic fracture.[3]

The American Association of Clinical Endocrinologists (AACE) defines postmenopausal osteoporosis as "a condition characterized by . . . low bone mass [and] microarchitectural deterioration of bone tissue, leading to bone fragility [and] a consequent susceptibility to fracture."[1] Patients are diagnosed with osteoporosis if a fracture involving minimal to no trauma occurs or a bone density scan shows bone mineral density (BMD) is greater than 2.5 standard deviations below the mean BMD value for young adult white women.

Calcium supplementation has long been promoted by the medical community and others for postmenopausal women and younger women whose dietary intake of calcium is inadequate as a way to decrease the risk of osteoporotic fractures. Several early studies demonstrated improvements in BMD[4–11] and reduced vertebral and non-vertebral fracture rates with the use of calcium and vitamin D.[10–15] These studies evaluated the effect of calcium supplementation alone,[10,11] vitamin D alone,[14] or both in combination on fracture prevention[12,13,15] (Table 1). The studies were randomized controlled trials; two included elderly men and postmenopausal women.[14,15] Adherence to treatment was generally good in most of the studies.[10,12,15] The average baseline dietary calcium intake in these studies ranged from 400 to more than 700 mg daily, and elemental calcium intake ranged from 480 to 1200 mg per day. One study in elderly institutionalized women with hyperparathyroidism found no difference in hip fracture rates between patients receiving calcium versus placebo, but that study was not of sufficient statistical power to detect a treatment effect.[16]

The practice of recommending calcium supplementation to postmenopausal women was widely accepted until a number of trials questioning the benefits of calcium supplementation in the prevention of fractures were published[17–21] and widely publicized by the media.[22]

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