Strontium for osteoporosis: to dose or to megadose?

Townsend Letter for Doctors and Patients, May, 2006 by Alan R. Gaby

Strontium has two different effects in bone. First, it is incorporated in small amounts into the hydroxyapatite crystal lattice, where it remains bound for years or decades and may improve bone quality. This effect probably occurs at "nutritional" doses, since dietary strontium is known to persist in the skeleton for long periods of time. Second, strontium atoms are adsorbed onto the surface of hydroxyapatite crystals, the probable site at which they stimulate bone formation, inhibit resorption, and increase BMD. This effect presumably occurs at higher doses, and the adsorbed strontium is rapidly cleared from bone after supplementation is discontinued. (10) Which of these effects is more important for fracture prevention is not known. However, if it is the former, then a small increase in strontium intake might reduce fracture incidence, even if it does not influence BMD.

The evidence is clear that strontium supplementation can help prevent osteoporotic fractures. Additional research is needed, however, to determine what dose provides the optimal balance of safety and efficacy.

Alan R. Gaby, MD

Financial disclosure: The author formulated and receives a royalty for a multivitamin-multimineral bone product that contains strontium.

References

1. Meunier PJ, et al. The effects of strontium ranelate on the risk of vertebral fracture in women with postmenopausal osteoporosis. N Engl J Med. 2004;350:459-68.

2. Kroes R, et al. Short-term toxicity of strontium chloride in rats. Toxicology. 1977;7:11-21.

3. El-Hajj Fuleihan G. Strontium ranelate--a novel therapy for osteoporosis or a permutation of the same? N Engl J Med. 2004;350:504-6.

4. Grynpas MD, Marie PJ. Effects of low doses of strontium on bone quality and quantity in rats. Bone. 1990;11:313-319.

5. A 2,000-kcal diet providing 30% of total energy from fat would weigh 417 grams (dry weight). Multiplying: 417 grams x 0.0019 = 792 mg.

6. A 2,000-kcal diet providing 30% of total energy from fat would weigh 417 grams (dry weight). Multiplying: 417 grams x 0.005 = 2.085 grams.

7. Ozgur S, et al. Rickets and soil strontium. Arch Dis Child. 1996;75:524-526.

8. Kroes R, et al. Short-term toxicity of strontium chloride in rats. Toxicology. 1977;7:11-21. This estimate was based on a human diet providing 2,000 kcal per day, with 30% of energy from fat (i.e., 417 grams of food per day, dry weight).

9. Meunier PJ, et al. Strontium ranelate: dose-dependent effects in established postmenopausal vertebral osteoporosis--a 2-year randomized placebo controlled trial. J Clin Endocrinol Metab. 2002;87:2060-2066.

10. Dahl SG, et al. Incorporation and distribution of strontium in bone. Bone. 2001;28:446-453.