Calcium Intake and Bone Mineral Density: Systematic Review
Calcium Intake and Bone Mineral Density: Systematic Review
Objective To determine whether increasing calcium intake from dietary sources affects bone mineral density (BMD) and, if so, whether the effects are similar to those of calcium supplements.
Design Random effects meta-analysis of randomised controlled trials.
Data sources Ovid Medline, Embase, Pubmed, and references from relevant systematic reviews. Initial searches were undertaken in July 2013 and updated in September 2014.
Eligibility criteria for selecting studies Randomised controlled trials of dietary sources of calcium or calcium supplements (with or without vitamin D) in participants aged over 50 with BMD at the lumbar spine, total hip, femoral neck, total body, or forearm as an outcome.
Results We identified 59 eligible randomised controlled trials: 15 studied dietary sources of calcium (n=1533) and 51 studied calcium supplements (n=12 257). Increasing calcium intake from dietary sources increased BMD by 0.6–1.0% at the total hip and total body at one year and by 0.7–1.8% at these sites and the lumbar spine and femoral neck at two years. There was no effect on BMD in the forearm. Calcium supplements increased BMD by 0.7–1.8% at all five skeletal sites at one, two, and over two and a half years, but the size of the increase in BMD at later time points was similar to the increase at one year. Increases in BMD were similar in trials of dietary sources of calcium and calcium supplements (except at the forearm), in trials of calcium monotherapy versus co-administered calcium and vitamin D, in trials with calcium doses of ≥1000 versus <1000 mg/day and ≤500 versus >500 mg/day, and in trials where the baseline dietary calcium intake was <800 versus ≥800 mg/day.
Conclusions Increasing calcium intake from dietary sources or by taking calcium supplements produces small non-progressive increases in BMD, which are unlikely to lead to a clinically significant reduction in risk of fracture.
Maintaining a calcium intake of at least 1000–1200 mg/day has long been recommended for older individuals to treat and prevent osteoporosis. Calcium supplements are commonly taken to achieve such intakes, which are considerably higher than the average intake of calcium in the diet in older people in Western countries, around 700–900 mg/day. Recently, concerns have emerged about the risk-benefit profile of calcium supplements. The small reductions in total fractures seem outweighed by the moderate risk of minor side effects such as constipation, coupled with the small risk of severe side effects such as cardiovascular events, kidney stones, and admission to hospital with acute gastrointestinal symptoms. Consequently, some experts have recommended that older people increase their calcium intake through their diet and take supplements only when that is not feasible. In a systematic review of calcium intake and fractures, we concluded that there was no evidence of an association between increased dietary calcium intake and lower risk of fracture. We identified only two small randomised controlled trials of dietary calcium intake that reported fracture as an outcome. Numerous cohort studies, however, assessed the relation between dietary calcium, milk or dairy intake, and risk of fracture, and most reported neutral associations.
The putative mechanism by which calcium intake affects bone health is by increasing bone mineral density (BMD). BMD is a surrogate endpoint for fracture risk that allows biological effects to be explored in randomised controlled trials of modest size. We investigated whether the results of randomised controlled trials with BMD as an endpoint support the recommendations to increase dietary calcium intake to prevent osteoporosis. We undertook a systematic review and meta-analysis of randomised controlled trials of dietary sources of calcium or calcium supplements in older adults (aged >50) to determine whether increasing intake from dietary sources has effects on BMD and, if so, whether they are similar to the effects of calcium supplements on BMD.
Abstract and Introduction
Abstract
Objective To determine whether increasing calcium intake from dietary sources affects bone mineral density (BMD) and, if so, whether the effects are similar to those of calcium supplements.
Design Random effects meta-analysis of randomised controlled trials.
Data sources Ovid Medline, Embase, Pubmed, and references from relevant systematic reviews. Initial searches were undertaken in July 2013 and updated in September 2014.
Eligibility criteria for selecting studies Randomised controlled trials of dietary sources of calcium or calcium supplements (with or without vitamin D) in participants aged over 50 with BMD at the lumbar spine, total hip, femoral neck, total body, or forearm as an outcome.
Results We identified 59 eligible randomised controlled trials: 15 studied dietary sources of calcium (n=1533) and 51 studied calcium supplements (n=12 257). Increasing calcium intake from dietary sources increased BMD by 0.6–1.0% at the total hip and total body at one year and by 0.7–1.8% at these sites and the lumbar spine and femoral neck at two years. There was no effect on BMD in the forearm. Calcium supplements increased BMD by 0.7–1.8% at all five skeletal sites at one, two, and over two and a half years, but the size of the increase in BMD at later time points was similar to the increase at one year. Increases in BMD were similar in trials of dietary sources of calcium and calcium supplements (except at the forearm), in trials of calcium monotherapy versus co-administered calcium and vitamin D, in trials with calcium doses of ≥1000 versus <1000 mg/day and ≤500 versus >500 mg/day, and in trials where the baseline dietary calcium intake was <800 versus ≥800 mg/day.
Conclusions Increasing calcium intake from dietary sources or by taking calcium supplements produces small non-progressive increases in BMD, which are unlikely to lead to a clinically significant reduction in risk of fracture.
Introduction
Maintaining a calcium intake of at least 1000–1200 mg/day has long been recommended for older individuals to treat and prevent osteoporosis. Calcium supplements are commonly taken to achieve such intakes, which are considerably higher than the average intake of calcium in the diet in older people in Western countries, around 700–900 mg/day. Recently, concerns have emerged about the risk-benefit profile of calcium supplements. The small reductions in total fractures seem outweighed by the moderate risk of minor side effects such as constipation, coupled with the small risk of severe side effects such as cardiovascular events, kidney stones, and admission to hospital with acute gastrointestinal symptoms. Consequently, some experts have recommended that older people increase their calcium intake through their diet and take supplements only when that is not feasible. In a systematic review of calcium intake and fractures, we concluded that there was no evidence of an association between increased dietary calcium intake and lower risk of fracture. We identified only two small randomised controlled trials of dietary calcium intake that reported fracture as an outcome. Numerous cohort studies, however, assessed the relation between dietary calcium, milk or dairy intake, and risk of fracture, and most reported neutral associations.
The putative mechanism by which calcium intake affects bone health is by increasing bone mineral density (BMD). BMD is a surrogate endpoint for fracture risk that allows biological effects to be explored in randomised controlled trials of modest size. We investigated whether the results of randomised controlled trials with BMD as an endpoint support the recommendations to increase dietary calcium intake to prevent osteoporosis. We undertook a systematic review and meta-analysis of randomised controlled trials of dietary sources of calcium or calcium supplements in older adults (aged >50) to determine whether increasing intake from dietary sources has effects on BMD and, if so, whether they are similar to the effects of calcium supplements on BMD.
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