Heated oyster shell with algal ingredient (AAACa) decreases urinary oxalate excretion

In nine normal subjects, four men and five women between 23 and 49 years of age, 800mg calcium was orally administered as active absorbable algal calcium (AAA Ca) (A) and calcium carbonate (CaCO3) (B), to compare with non-calcium-containing placebo (C) in a crossover design. Calcium, oxalate, osmolality, creatinine, and pH were measured in the first three morning urine samples and Ca/osmolality, Ca/osmolality/body weight, Ca/creatinine, and oxalate/ osmolality were calculated to correct for urine dilution. Ca x oxalate product was also calculated, and Ca oxalate crystal in the sediment was microscopically examined, semiquantitatively estimated as -, +, ++, or , and numerically expressed as 0, 1, 2, or 3, respectively. Urinary Ca excretion was similar in groups A and B, but significantly larger than in group C, regardless of the method of correction for dilution. Urinary oxalate excretion with correction for osmolality, however, was significantly lower in A than in B and C, which gave similar values. Urine pH was similar among all three groups. Ca x oxalate product was significantly higher in C than in A, but A and B were not significantly different. AAA Ca appeared to decrease urinary oxalate excretion and Ca x oxalate product more efficiently than CaCO3, suggesting the possibility of inhibiting the formation of Ca x oxalate kidney stones.