Strontium is found naturally in the human skeleton.
The level of strontium in bone tissue is approximately 3.5% of the calcium content of bone.
Strontium taken orally through the diet and from supplements is preferentially incorporated into the teeth and bones.
Research suggests that the oral absorption of strontium is dependent on age and decreases with increasing age.
Scientists have suggested two methods of absorption of strontium from the gastrointestinal tract: passive diffusion and carrier-mediated absorption.
In adults, strontium is absorbed to a lesser extent than calcium, possibly due to the larger molecular size of strontium in comparison to the calcium molecule.
Both calcium and strontium compete with one another for absorption in the intestines. High dietary intake of calcium has been shown to reduce concurrent absorption of strontium.
It has been proposed that when both elements are present together, twice the amount of calcium is absorbed from the intestines in comparison with strontium.
Animal studies suggest that extremely high dietary intakes of strontium, in the absence of adequate calcium intake, can actually disturb bone mineralization.
At such concentration levels strontium replaces calcium ions in bone. The unbalanced incorporation of strontium into bone tissue in the place of calcium may cause a disturbance of the bone lattice, resulting in decreased bone mineral density.
It is precisely for this reason that calcium intake must be adequate when supplementing with strontium.
Further studies in animals reveal that strontium given as a part of the normal diet (when calcium intake is adequate) may have profound effects on bone formation and density.
Oral administration of strontium doses to rats was shown to enhance the rate of bone formation and trabecular bone density.