Strontium is a naturally occurring trace element found in the earth’s crust, water, and foods, and it is chemically similar to calcium. About 99% of the strontium absorbed by the human body is concentrated within the skeletal system, which is why researchers have investigated its potential to support bone structure. Its presence in bone has led to studies exploring its use in managing bone diseases that involve a loss of density and strength. This investigation looks into the scientific understanding of how strontium influences skeletal health and the differences between its various forms.
How Strontium Interacts with Bone Tissue
Strontium influences the bone remodeling cycle through a unique, dual mechanism that affects both bone-building (osteoblasts) and bone-resorbing (osteoclasts) cells. Bone is a dynamic tissue constantly undergoing renewal. Strontium appears to shift this balance toward formation.
The element actively encourages osteoblast activity, stimulating the cells responsible for synthesizing bone matrix proteins, such as collagen. This stimulation promotes the proliferation and differentiation of these cells, leading to an increase in the rate of new bone formation. Strontium’s chemical resemblance to calcium allows it to interact with the calcium-sensing receptor (CaSR) on the surface of bone cells, which is believed to mediate some of these beneficial effects.
Strontium also inhibits the function of osteoclasts, the cells that resorb aged or damaged bone tissue. By reducing the formation and differentiation of these cells, the element decreases the overall rate of bone breakdown. This dual action—increasing bone formation while decreasing bone resorption—results in an overall gain in bone mineral density and an improvement in the microarchitecture of the bone.
Once absorbed, strontium is incorporated directly into the crystal structure of the bone mineral, hydroxyapatite, replacing some of the calcium ions. The unique way strontium modulates the activity of both cell types involved in bone turnover distinguishes it from many traditional treatments, which typically focus on either stimulating formation or inhibiting resorption alone.
The Critical Difference Between Strontium Forms
The element strontium is available in two vastly different chemical forms with distinct regulatory statuses and safety profiles. The first form, strontium ranelate, has been studied extensively in clinical trials as a pharmaceutical product.
Strontium ranelate is a synthetic compound where the strontium ion is bound to ranelic acid, and it was historically marketed under brand names like Protelos or Protos. This compound was prescribed at a relatively high daily dose of 2 grams to treat osteoporosis, demonstrating effectiveness in reducing fracture risk in certain populations. However, its use has become severely restricted or withdrawn in many countries, including the United States, Canada, and the European Union, due to safety concerns.
The high-dose prescription form has been linked to a small increase in the risk of serious side effects, notably cardiovascular events and venous thromboembolism (blood clots in the veins). Regulators determined that the risks of the medication outweighed the benefits for many patients, leading to its limited availability. The ranelate component, the synthetic acid, is unique to this drug formulation.
In contrast, strontium citrate and strontium carbonate are the forms commonly sold as over-the-counter dietary supplements. These supplements are not regulated as drugs and typically contain lower amounts of elemental strontium than the prescription ranelate. The severe side effects, such as blood clots and cardiac issues, have been associated with the high, pharmacologic dose of strontium ranelate, not generally with the lower-dose supplement forms.
The primary difference lies in the regulatory pathway and the dose; strontium ranelate is a restricted drug with known severe risks, whereas strontium citrate is a readily available supplement. This distinction is why consumers must be aware of which form they are considering, as they are not interchangeable in terms of safety or regulation.
Safety Considerations and Potential Side Effects
While strontium citrate supplements are widely accessible, their usage requires careful consideration, particularly regarding dosage and patient health status. The typical recommended daily intake for elemental strontium in supplement form often falls around 680 milligrams, which is substantially higher than the 0.5 to 1.5 milligrams a person typically obtains from their diet each day.
Common side effects associated with the supplement form can include mild gastrointestinal upset, such as nausea or diarrhea. These effects are usually transient and may resolve as the body adjusts to the supplement. Individuals with pre-existing conditions need to exercise caution before beginning a strontium regimen.
The kidneys are responsible for eliminating strontium from the body, meaning individuals with impaired renal function should be cautious with supplementation. Strontium can accumulate if the kidneys are not functioning properly, which could alter its effects on bone. Consultation with a healthcare provider to assess renal function is advisable before starting any new supplement.
Strontium also competes with calcium for absorption in the digestive tract because of their chemical similarity. Therefore, it is important to take strontium supplements at least two to four hours apart from calcium supplements or calcium-rich foods to maximize absorption of both minerals. Additionally, strontium may interact with certain antibiotics, such as quinolones and tetracyclines, and should be temporarily discontinued while taking those medications.
As a precaution, individuals with a history of cardiovascular disease or blood clotting disorders are generally advised to avoid all forms of strontium supplementation.