Strontium citrate — The Bone-Building Mineral
Strontium citrate is a highly bioavailable form of the trace mineral strontium, which shares chemical similarities with calcium and is preferentially deposited in bone tissue. In the context of longevity, it is primarily utilised to preserve skeletal integrity and combat age-related bone loss, a critical factor in maintaining mobility and preventing frailty in older adults.
Mechanism of Action
Strontium is a trace mineral that closely mimics calcium in the body, allowing it to be incorporated directly into the hydroxyapatite crystal lattice of bone tissue. It exerts a dual mechanism of action on bone remodelling: it stimulates osteoblast differentiation and bone formation via activation of the calcium-sensing receptor (CaSR) and downstream Wnt/β-catenin signalling. Simultaneously, it inhibits osteoclast-mediated bone resorption by decreasing the expression of RANKL and increasing osteoprotegerin (OPG). This uncoupling of the bone remodelling cycle leads to a net increase in bone mass and structural integrity.
Human Trial Evidence
Human evidence for strontium citrate specifically is limited but positive, primarily focusing on bone mineral density. The MOTS (Melatonin-micronutrients Osteopenia Treatment Study) trial demonstrated that a combination of strontium citrate, melatonin, vitamin D3, and vitamin K2 significantly improved bone mineral density in osteopenic women over one year. Most large-scale human longevity and fracture-reduction trials have historically used strontium ranelate rather than the citrate form.
Dosing Protocol
450–680 mg/day of elemental strontium (often as strontium citrate) is the most commonly studied and utilised range in human trials and clinical practice. It is typically taken at night on an empty stomach, well separated from calcium supplements or calcium-rich foods, as calcium and strontium compete for the same absorption pathways.
Safety & Contraindications
Strontium citrate is generally well tolerated, with mild gastrointestinal distress (nausea, diarrhoea) being the most common side effect. Because strontium is heavier than calcium, its incorporation into bone artificially inflates DEXA scan results, requiring mathematical correction to accurately assess true bone mineral density. It should be used with caution in individuals with severe renal impairment, as it is primarily excreted by the kidneys. There is a theoretical risk of cardiovascular events based on data from strontium ranelate, though this has not been definitively linked to the citrate form.