The mineral strontium is attracting a great deal of interest as a new treatment for osteoporosis. It is now approved for use in the UK as an alternative to bisphosphonates, but has not yet had FDA approval in the US.
Strontium lies directly below calcium on the periodic table of elements. Calcium, strontium and magnesium all belong to the same chemical family so strontium is an element with properties similar to calcium. In the 1940s it was discovered that the body contains significant amounts of the mineral and that 99 percent of it is in the skeleton. Strontium appears to play a crucial role in bone remodeling as it tends to migrate to sites in bone where active remodeling is taking place.
Strontium was first discovered in ore near the Scottish town of Strontian in 1790. Natural strontium is stable, non-radioactive and appears to be nontoxic and is not to be confused with man-made strontium-90 – a radioactive form which is extremely toxic in high doses and linked to bone cancer, and leukemia. Strontium-90 was dispersed though-out the world as a result of nuclear fallout from atomic bomb testing.
Strontium ranelate (Servier Laboratories Ltd) is composed of two atoms of stable strontium (and one molecule of ranelic acid). Two large randomized controlled trials have shown a significant reduction in fractures compared to placebo and significant increases in bone density over three years in postmenopausal women using strontium ranelate. Of interest, the evidence shows benefit in the over 80 age group – something that no other anti-osteoporosis treatment has demonstrated. Strontium is unique in that it has the dual effect on bone metabolism of increasing bone formation and decreasing bone resorption – something that bisphosphonates, HRT and SERMS which are anti-resportive only, cannot do. Of note, strontium slows bone resporption, but doesn’t kill osteoclast cells as bisphosphonates do.
Earlier smaller studies observed decreased bone pain and an increase in bone formation in people taking quite high doses of strontium. These and other independent studies used many different forms of strontium including strontium lactate, gluconate, carbonate, chloride. They all appear to have the bone building action. Many of these forms have poor gastric tolerance – that is, they are more likely to cause upset stomach or diarrhea. The synthetic ranelic acid salt has better gastric tolerance.
Of particular interest, strontium lactate, citrate, gluconate and carbonate are all natural unpatentable forms of strontium. Ranelic acid is a purely synethic molecule and by adding it to strontium it creates a patentable form. It is questioned whether it adds anything to the treatment effectiveness – and whether strontium alone is the beneficial portion.
Strontium ranelate is not cheap and is currently approximately the same cost per month as Fosamax . Strontium citrate appears to be a form of strontium that is relatively easily absorbed, is very soluble, and has good gastric tolerance. Because citrate is a natural ligand it can be purchased as a dietary supplement rather than a drug.
The absorption of strontium ranelate is reduced by food, milk and derivative products. It should therefore be administered between meals, preferably at bedtime or at least 2 hours after eating.
Calcium should not be taken at the same time as strontium since calcium dramatically decreases the absorption of the strontium.
It is currently only recommended for use with postmenopausal women.
Traditional bone mineral tests like the DEXA will give artificially high results as strontium is much denser than calcium.
The long term safety and effectiveness of strontium is not known.
Strontium: The First Bone Builder. The rediscovery of a forgotten bone health mineral. Advances in Orthomolecular Research. 2005: 2; 7
Meunier PJ, Roux C, Seeman E, et al. The effects of Strontium Ranelate on the risk of vertebral fracture in women with postmenopausal osteoporosis. NEJM 2004 350;459 -68
Reginster JY, Seeman E, DE Vernejoul MC, et al . Tropos Study. J Clin Endocrinol Metab 2004–1774
Strontium ranelate reduces the risk of nonvertebral fractures in post-menopausal women with osteoporosis: