Strontium is a naturally occurring trace element that is chemically similar to calcium. However, because of their few differences (e.g., size), strontium and calcium aren’t biologically equivalent, and they can compete for absorption and utilization in the body.^[13]

A typical diet contains 2–4 mg of strontium per day, mostly from plant-based (grain and vegetable) sources.^[15][14] However, estimates have ranged from 1.4–5.7 mg per day, too.^[16] The amount of strontium in a given food source varies by the amount of strontium in the soil, which may explain the variability in intake estimates.^[15][14]

The currently available evidence does not demonstrate the benefits of strontium formulations that can be obtained for oral supplementation over the counter. Though clinical evidence is lacking, the available preclinical evidence suggests that strontium could improve bone strength (preventing bone loss and fractures related to bone loss).^[16][15][14]

When used as an additive to toothpaste or creams and applied topically, strontium has been shown clinically to reduce dental and skin sensitivities or irritation.^{[17][5][6][16][2][3][4]}

Because of their similarities, strontium and calcium compete in the body. For example, strontium competes with calcium for absorption, notably in the intestines and renal tubules.^[15] Calcium tends to be preferred physiologically, though, so taking the two minerals together may reduce the absorption and retention of strontium. Strontium absorption is reduced by phosphate and increased by vitamin D.^[13] For these reasons, supplement labels will often recommend taking these supplements separately and also ensuring that adequate calcium is consumed.^[1][14][15]

As we age, how the body differentiates between strontium and calcium can vary. In early childhood, during bone development, excess exposure to strontium can impede bone growth and cause strontium-induced rickets. Though these risks are not as concerning for adults, strontium can still interfere with normal bone development when taken in circumstances where vitamin D, phosphorus, and calcium intakes are insufficient.^[13][16]

In observational evidence on hypertension in pregnancy, higher blood strontium levels were associated with hypertensive disorders, but a clear cause-and-effect relationship could not be determined.^[18]

Bone strength is maintained through cycles of bone formation and resorption via specialized cells called osteoblasts (formation) and osteoclasts (resorption). When bone resorption starts to exceed bone formation, bone strength suffers, leading to conditions like osteoporosis.^[19]

When absorbed, almost all of the strontium ends up in bones, teeth, and joint structures.^[16] Once incorporated into the bone, calcium and strontium appear to behave similarly.^[15][14][16] Strontium may promote the new formation of bone by increasing the number of osteoblasts and preventing their destruction.^[14][16]

Though we still don’t have a complete understanding of how strontium works in the body, one possible mechanism may be that it works its way into bone cells to fill the gaps left by excessive resorption.^[15][14] When used as a toothpaste additive, strontium is believed to work by blocking the exposed dentine tubules that produce dental hypersensitivity.^[17][5][6]

In some preclinical (animal) studies, strontium seems to reduce pro-inflammatory cytokines to reduce inflammation.^[16] If the same anti-inflammatory activity occurs in humans, that could explain why it has shown some evidence of being useful for reducing skin irritation and itching as part of topical ointments.^[2][3][4]