Strontium supplements are promoted as a “natural” way “to maintain strong bones.” One product calls itself “Bone Maker.” And some calcium supplements now include small amounts of strontium.
Strontium, a common metallic element, is not classified as a nutrient, but the human body can absorb it and use it as if it were calcium. Like calcium, it always comes bound to other elements. Most supplements contain strontium citrate. Another form, strontium ranelate, is patented and sold only as a prescription drug for osteoporosis in Europe and Australia. This form has been shown in clinical trials to boost bone mineral density and reduce fractures. It seems to work primarily by reducing bone loss (resorption), similar to most other osteoporosis drugs (notably bisphosphonates). Some researchers have proposed that strontium ranelate may also stimulate bone formation.
A strontium update
Since we last reported on strontium in 2012, there has been further support for its effectiveness, but also some concerns about its safety. Worth noting is that all published studies have used strontium ranelate, with nearly all funded by the pharmaceutical company that makes it or done by scientists with financial ties to the company.
- For bones. According to a 2013 review in Therapeutic Advances in Musculoskeletal Disease, long-term use of strontium ranelate (up to 10 years so far) improves bone mineral density in women, with the authors noting that it is cost-effective, especially in women over 70. Though most studies have focused on women, there’s some evidence that strontium helps men too. In a 2013 study in the Journal of Clinical Endocrinology & Metabolism, men with osteoporosis who took strontium ranelate for two years had evidence of increased bone density in the spine and hip.
- For joints. Preliminary research suggests that strontium may also benefit arthritic joints by stimulating cartilage formation, among other possible mechanisms. In a large study in the Annals of the Rheumatic Diseases in 2013, people with knee osteoarthritis took strontium ranelate (1 or 2 grams a day) or a placebo for three years. Both strontium groups showed less joint space narrowing on X-rays (indicating slower disease progression) than the placebo group. The higher-dose group also had improvements in knee pain and physical functioning.
But is it safe?
Research on strontium’s side effects and risks has been inconsistent. A 2013 study in Rheumatology International confirmed the “good safety profile of strontium ranelate in the management of postmenopausal osteoporosis,” based on data from 12,000 women. Gastrointestinal problems were most frequently reported. Several other studies found no overall increased risk of heart attacks, unstable angina, or cardiovascular death in people on strontium, compared to those on other osteoporosis drugs.
On the other hand, the European Medicines Agency recently cautioned that people should take strontium ranelate only for severe osteoporosis and only if they cannot be treated with other medications, that they be frequently monitored, and that they stop if they develop cardiovascular problems. This advice was based on a pooled analysis of studies that affirmed strontium ranelate’s fracture-reducing effects but also showed increased risk of cardiac events and blood clots in people with a history of heart or circulatory problems. The agency recommends against the use of strontium ranelate by anyone with a history of heart attacks, blood clots, stroke, peripheral artery disease, or uncontrolled hypertension. Other possible adverse effects include liver inflammation, seizures, and a drop in red blood cell counts.
Another concern is that strontium can inflate bone density readings because the element has a higher atomic weight than calcium, which it replaces in bone (thus bones may appear stronger than they really are). Researchers usually adjust for this when reporting bone density in strontium studies.
Bottom line: Though the research on strontium is encouraging, we don’t recommend supplements. More studies—including independent ones—are needed to assess its longer-term benefits for both bones and joints, as well as its potential risks. Moreover, strontium citrate (the form available in supplements) has not been well-studied, and it’s not known if it has the same effects, good or bad, as strontium ranelate. Keep in mind also that, unlike strontium ranelate, strontium supplements are not regulated or standardized, and an optimal dose has not been established for them.