Ocular and systemic safety evaluation of calcium formate as a dietary supplement.
OBJECTIVE
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.
Altaweel
Michael M
MM
Department of Ophthalmology and Visual Science, School of Medicine and Public Health, University of Wisconsin-Madison, WI, USA.
Hanzlik
Robert P
RP
Ver Hoeve
James N
JN
Eells
Janis
J
Zhang
Baoyan
B
D000284:Administration, Oral; D000328:Adult; D050071:Bone Density Conservation Agents / Q000009:adverse effects* / Q000097:blood; D055253:Color Vision / Q000187:drug effects*; D019587:Dietary Supplements; D004334:Drug Administration Schedule; D004596:Electroretinography; D005074:Evoked Potentials, Visual / Q000187:drug effects; D005260:Female; D005561:Formates / Q000009:adverse effects* / Q000097:blood; D006801:Humans; D008875:Middle Aged; D010024:Osteoporosis / Q000188:drug therapy; D011446:Prospective Studies; D014787:Vision Tests; D014792:Visual Acuity / Q000187:drug effects; D014794:Visual Fields / Q000187:drug effects
D050071:Bone Density Conservation Agents; D005561:Formates; C030544:formic acid