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Increasing calcium intake not always effective for bone health, fracture prevention
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Findings from two studies recently published in The BMJ suggest that increasing calcium intake through dietary sources or supplements does not improve bone health or prevent fracture in older adults.
Increasing calcium intake should not be recommended for preventing fracture, according to the researchers.
Current NIH guidelines recommend that men and women aged 50 years and older consume at least 1,000 mg to 1,200 mg per day of calcium to help improve bone density and prevent fractures.
“Firstly, we found that increasing calcium intake either from the diet or by taking calcium supplements led to similar, small, one-off increases in bone density of 1% to 2%,” Mark J. Bolland, MBChB, PhD, associate professor in the department of medicine at the University of Auckland in New Zealand, told Endocrine Today. “These increases do not build up over time and are too small to produce significant reductions in the chance of having a fracture. Secondly, the level of dietary calcium intake is not associated with the risk of having a fracture. Thirdly, in clinical trials, calcium supplements have only small, inconsistent benefits on preventing fractures, with no effect of fractures seen in the highest quality trials.”
Risk for fracture
In the first study — a systematic review of randomized controlled trials and observational studies of calcium intake with fracture as an endpoint — Bolland and colleagues assessed evidence that supports recommendations to increase calcium intake through dietary sources or supplements to prevent fractures.
The researchers evaluated two randomized controlled trials of dietary sources of calcium and 50 reports from 44 cohort studies of the associations between dietary calcium or dairy intake and fracture outcomes.
Most studies showed no association between calcium intake and fracture risk. Similarly, results did not show associations between milk and dairy intake and fractures.
Based on 26 randomized controlled studies that evaluated the effect of calcium supplements on the risk for fracture, supplements reduced the risk for total fracture (RR = 0.89; 95% CI, 0.81-0.96) and vertebral fracture (RR = 0.86; 95% CI, 0.74-1); however, no effect was found for hip or forearm fracture.
“Calcium supplements have small inconsistent benefits on fracture reduction but probably have an unfavorable risk-benefit profile,” the researchers wrote. “There was no risk reduction in fracture at any site in pooled analyses of the randomized controlled trials of calcium supplements at lowest risk of bias, and there was evidence of publication bias in small- [and] moderate-sized trials. Collectively, these results suggest that clinicians, advocacy organizations and health policymakers should not recommend increasing calcium intake for fracture prevention, either with calcium supplements or through dietary sources.”
Improving BMD
In the second study, Bolland and colleagues conducted a random effects meta-analysis of randomized controlled trials to determine whether increasing calcium intake through dietary sources affects bone mineral density and whether the effects are similar to those of calcium supplements. Dietary sources included milk or milk products, dairy products and hydroxyapatite preparations. Calcium supplements included calcium monotherapy and co-administered calcium and vitamin D supplements.
Fifteen studies evaluated the dietary sources of calcium, and 51 evaluated calcium supplements.
BMD increased by 0.6% to 1% at the total hip and total body at 1 year and by 0.7% to 1.8% at the total hip, total body, lumbar spine and femoral neck at 2 years after increasing calcium intake from dietary sources. No effect on BMD in the forearm was found.
BMD increased at all sites after calcium supplementation by 0.7% to 1.4% at 1 year, 0.8% to 1.5% at 2 years and 0.8% to 1.8% at more than 2.5 years.
Increases in BMD were similar throughout the different trials.
BMD increased similarly through dietary sources and calcium supplements; however, the increases were small and little effect was found on BMD after a year, according to Bolland.
“Subgroup analyses do not suggest greater benefits of increasing calcium intake on BMD in any subpopulation based on clinically relevant baseline characteristics,” the researchers wrote. “The small effects on BMD are unlikely to translate into clinically meaningful reductions in fractures. Therefore, for most individuals concerned about their bone density, increasing calcium intake is unlikely to be beneficial.”
Revisiting recommendations
In an accompanying editorial, Karl Michaëlsson, MD, PhD, a professor in the department of surgical sciences at Uppsala University in Sweden, wrote that nearly the whole populations of adults aged at least 50 years are indicated for increasing calcium and vitamin D through recommended guidelines in the United States.
“In general, supplementation with calcium, with or without vitamin D, does not confer a reduced risk of fracture,” Michaëlsson told Endocrine Today. “If you eat a normal varied diet, there seems to be no need to increase your calcium intake by a dietary change or by calcium supplement use. We need to better define true deficiency levels of calcium intake and of vitamin D status.”
Bolland added that more research is needed regarding the recommendations, especially when evidence has suggested that increasing calcium intake is unlikely to prevent fractures.
“For most patients who are concerned about their bone health, they do not need to worry about their calcium intake,” Bolland said. – by Amber Cox
- References:
- Bolland MJ, et al. BMJ. 2015;doi:10.1136/bmj.h4580.
- NIH. Calcium: Dietary Fact Sheet. Available at: ods.od.nih.gov/factsheets/Calcium-HealthProfessional/#h2. Accessed Oct. 20, 2015.
- Michaëlsson K. BMJ. 2015;doi:10.1136/bmj.h4825.
- Tai V, et al. BMJ. 2015;doi:10.1136/bmj.h4183.
- For more information:
- Mark J. Bolland, MBChB, PhD, can be reached at m.bolland@auckland.ac.nz.
Disclosure: Bolland reports being a recipient of the Sir Charles Hercus Health Research Fellowship. Michaëlsson reports no relevant financial disclosures. Please see the full studies for a list of all other authors’ relevant financial disclosures.
Perspective
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Pauline M. Camacho, MD FACE
I do not disagree with the findings in these two studies showing the minimal effect of calcium on bone density and its inconsistent effect on fracture risk. We all see this in our clinical practices. That is why calcium simply cannot be relied on as the sole therapy for osteoporosis. Pharmacologic therapy definitely reduces fracture risks more effectively than calcium alone.
It is important to recognize that the vast majority of patients with osteoporosis probably are calcium deficient. Their nutritional intake is often insufficient, gastrointestinal calcium absorption diminishes with age, and vitamin D deficiency is very common. Therefore, the question becomes this: How effective then are pharmacologic agents in the setting of calcium deficiency? Are we maximizing the full potential of these agents in reducing fracture risk by giving them to a calcium-deficient population? Even more important: How safe are these drugs in the setting of calcium deficiency? Antiresorptive agents, particularly the injectable agents denosumab and zoledronic acid, are quite potent and may cause hypocalcemia in the setting of calcium or vitamin D deficiency. Achieving calcium balance is definitely a very important component of successful osteoporosis management.
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