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Strontium ( /?str?nti?m/) is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and strontianite. The 90Sr isotope is present inradioactive fallout and has a half-life of 28.90 years. Both strontium and strontianite are named after Strontian, a village in Scotland near which the mineral was first discovered.
Effect on the human body
The human body absorbs strontium as if it were calcium. Due to the elements being sufficiently similar chemically, the stable forms of strontium might not pose a significant health threat—in fact, the levels found naturally may actually be beneficial (see below) — but the radioactive 90Sr can lead to various bone disorders anddiseases, including bone cancer. The strontium unit is used in measuring radioactivity from absorbed 90Sr.
The drug strontium ranelate, made by combining strontium with ranelic acid, was found to aid bonegrowth, increase bone density, and lessen vertebral, peripheral and hip fractures. Women receiving the drug showed a 12.7% increase in bone density. Women receiving a placebo had a 1.6% decrease. Half the increase in bone density (measured by x-ray densitometry) is attributed to the higher atomic weight of Sr compared with calcium, whereas the other half a true increase in bone mass. Strontium ranelate is registered as a prescription drug in Europe and many countries worldwide. It needs to be prescribed by a doctor, delivered by a pharmacist, and requires strict medical supervision. Currently (early 2007), it is not available in Canada or the United States.
There is a long history of medical research regarding strontium’s benefits, beginning in the 1950s. Studies indicate a lack of undesirable side-effects.Several other salts of strontium such as strontium citrate or strontium carbonate are available in the United States under the Dietary Supplements Health and Education Act of 1994, providing close to the recommended strontium content, about 680 milligrams per day, of strontium ranelate. Their long-term safety and efficacy have not been evaluated on humans in large-scale medical trials.