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Strontium: Calcium
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Strontium is in row IIa of the periodic table, just below calcium. Like calcium, strontium has two positive charges in its ionic form. Because of its chemical similarity to calcium, strontium can replace calcium to some extent in various biochemical processes in the body, including replacing a small proportion of the calcium in hydroxyapatite crystals of calcified tissues such as bones and teeth. Strontium in these crystals imparts additional strength to these tissues. Strontium ... appears to draw extra calcium into bones. When rats or guinea pigs are fed increased amounts of strontium, their bones and teeth became thicker and stronger.
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Strontium is a trace element closely chemically related to calcium and both utilize the same carrier protein for transport. Strontium has both anabolic (bone building) effects and anti-resorption (anti-depleting) effects, and ... may have significant beneficial effects on bone balance.
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Strontium imitates the in-vivo behaviour of calcium and is preferentially taken up by bone, concentrating at sites of high skeletal metabolic activity. The radioactive half life of Strontium is 50.5 days with a biological half life of about 14 days in normal bone due to renal and to a lesser extent biliary excretion. Due to the high affinity of osteoblastic skeletal metastases for this isotope, Strontium is retained almost indefinitely within metastatic bone.
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Strontium-90 is one of the most dangerous of the radioactive fission fragments from nuclear fission since it has a relatively short half-life (29 yr) and tends to be taken up by living organisms. Vertibrates which need calcium will take up strontium-90 since it is so chemically similar to calcium, and it will therefore remain in bones and teeth to be a continuing source of ionizing radiation. It was one of the most troublesome constituents of the fallout from nuclear weapons testing.
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Strontium, a naturally occurring mineral in the same mineral family as calcium and magnesium, has been shown to promote bone growth in both human and animal studies. Strontium occurs in nature in soil, foods, and bones.
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Strontium comprises about 0.025 percent of the Earth's crust; its cosmic abundance is estimated as 18.9 atoms (Si = 106 atoms). Although it is widely distributed with calcium, there are only two principal ores of strontium alone, celestine (SrSO4) and strontianite (SrCO3).
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