Ocular and systemic safety evaluation of calcium formate as a dietary supplement.

James Verhoeve // Michael Altaweel // Publications // Jun 01 2009

PubMed ID: 19456257

Author(s): Altaweel MM, Hanzlik RP, Ver Hoeve JN, Eells J, Zhang B. Ocular and systemic safety evaluation of calcium formate as a dietary supplement. J Ocul Pharmacol Ther. 2009 Jun;25(3):223-30. doi: 10.1089/jop.2008.0128. PMID 19456257

Journal: Journal Of Ocular Pharmacology And Therapeutics : The Official Journal Of The Association For Ocular Pharmacology And Therapeutics, Volume 25, Issue 3, Jun 2009

PURPOSE The objective of this study was to perform a preliminary evaluation of the ocular and systemic safety of calcium formate, a dietary calcium supplement for prevention and management of osteoporosis. Although formate is an endogenous product of metabolism, high concentrations are associated with toxicity during methanol overdose.

METHODS In this prospective clinical trial, 12 healthy women ingested calcium formate (1,300 mg) three times a day for 14 days. Study evaluations included physical and ocular examination, extensive laboratory testing, serum calcium and formate levels, Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity, color vision, visual fields, visual evoked potential (VEP), and full-field, pattern, and multifocal electroretinograms (MERG).

RESULTS The mean baseline serum level of formate was 0.572 +/- 0.06 mM. Peak serum levels and final serum formate did not differ significantly from baseline. The final concentration was 0.582 +/- 0.091 mM. Accumulation of serum formate did not occur. There was also no evidence of toxicity with calcium formate ingestion. All examinations and tests remained normal, including optic nerve and retinal function. Three subjects had mild transient symptoms attributable to any calcium formulation.

CONCLUSIONS Calcium formate is highly bioavailable and well-tolerated. Serum formate remained at basal levels and did not accumulate with repeated dosing. Systemic and ocular safety was demonstrated by objective testing. Given its high oral bioavailability, calcium formate may be a good choice for calcium supplementation in the prevention and management of osteoporosis. Further study will be needed to evaluate its long-term safety in a larger group of subjects representing more varied age, health, dietary, and nutritional status.