Strontium for Bone Health
How Strong is the Evidence in 2009?
The case: At a multidisciplinary conference, a patient taking strontium as a nutritional supplement for her bones was presented. Many of the professionals at the conference were largely uninformed about this treatment.
Potential Value of Strontium Long Known
Studies in the 1950s demonstrated that strontium by mouth could increase bone density. But interest in developing the potential treatment lagged. One reason probably was the public’s fear of dangers related to radioactive strontium.
Radioactive Strontium
Strontium is a metal, similar to calcium. In its natural state, it is usually in igneous rocks, and is not radioactive. However, radioactive strontium can be produced by nuclear fission, and can be a product of nuclear explosion fallout. Nuclear testing spread radioactive strontium in the 1950s and again from accidents as recently as 1986 with the Chernobyl disaster. Radioactive strontium can cause cancer, especially bone cancer.
Radioactive strontium also has peaceful uses: it is used as a treatment to fight bone cancer, and may be used as a power source in space craft.
Strontium Replaces Bone Calcium
Non-radioactive strontium can adhere to bone. Some enters the bone. Measurements show increased bone density after taking strontium. Some of the apparent increase is just because strontium itself is denser than calcium, but experts can account for that effect; the remaining increase is thicker bone.
The thickness comes from its effect on bone turnover. Healthy bones are living tissue, with continuous breakdown and rebuilding. Strontium stimulates the formation of osteoblasts. These bone cells have two functions: they form new bone, and they inhibit osteoclasts—the cells that breakdown bone. Strontium then both increases bone production and decreases bone breakdown.
The Evidence for Strontium
Nutritional supplements do not need scientific studies unless they claim to prevent or treat a disease, so studies examining commercial non-prescription products are generally not available.
However, if a manufacturer makes a claim that a product prevents or treats a disease, regulations in the US, Canada, and most western countries require proof of the product’s efficacy.
Strontium ranelate is the only preparation that has claims that it treats or prevents osteoporosis and osteopenia. Clinicians look to the Cochrane Collaboration for non-biased authoritative information of effectiveness. Cochrane reviewers found only four studies of strontium ranelate that met validity criteria. The Cochrane review summarized and evaluated these studies.
Bone density. For back bone (vertebral) density, to achieve minimal improvement, three women need to be treated for one to have benefit (the number needed to treat, NNT, was three; this is generally accepted to be a good effect). For the hip, similar results were found.
Fractures. Bone density by itself is not important. The real purpose of treatment would be to reduce the risk of fractures. For vertebral fractures, women taking strontium ranelate had about half the risk of those taking placebo. For hip fractures, only one study reported adequate data, and strontium offered no significant benefit. The other studies reported “non-vertebral fractures,” which included hip fractures, and the benefit from pooled data was almost none (confidence interval close to one).
Adverse effects. During treatment, the only reported adverse effect was a small increase in risk of diarrhea. There is a theoretical risk of stroke and other vascular problems.
Issues of Strontium Use
Can the evidence for strontium ranelate be extrapolated to nutritional supplements available in the US and Canada? This is a matter of speculation.
The long term effects of strontium are unknown. Strontium does become incorporated into bone, and how that effects bone quality is as yet unclear.
How does strontium ranelate compare to existing prescription treatments such as biphosphonates? Will it be worth any extra cost?
Summary
Little is known about the risks and benefits of strontium nutritional supplements. A prescription preparation, strontium ranelate, has evidence that it improves bone density, and reduces the risk of vertebral fractures. Evidence that it reduces hip fracture risk is weaker. Short term use of strontium preparations seems to have little risk except for a low risk of diarrhea. Long term effects of strontium are unknown. Perhaps most important are other considerations. “Compliance with therapy is poor” and “women should be encouraged to embrace lifestyle changes that benefit bone health.” (de Villiers TJ. Best Practices Research and Clinical Obstetrics and Gynaecology. 2009 Feb;23(1):73-85
Main Source: O’Donnell S, Cranney A, Wells GA, Adachi J, Reginster JY. Strontium ranelate for preventing and treating postmenopausal osteoporosis. Cochrane Database of Systematic Reviews 2006, Issue 4. Art. No.: CD005326. DOI: 10.1002/14651858.CD005326.pub3
Does Strontium Strengthen bones?
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