Calcium absorption from the ingestion of coral-derived calcium by humans

Recent dietary life involves frequent opportunities for the ingestion of pu rified, processed food products and preserved foods, and it has been pointe d out that the current dietary mineral intake strongly tends toward nutriti onal imbalance. The Ryukyu Islands yield coral which contains calcium and m agnesium in a content ratio of about 2 to 1, with their approximate content s of 20 and 10%, respectively. In this report, the calcium absorption from the ingestion of crackers into which the coral powder was incorporated (cor al-added crackers) and that from ingestion of calcium carbonate-added crack ers was comparatively assessed. Twelve healthy adult volunteers (6 men and 6 women) ingested coral-added crackers (calcium content: 525 mg) and calciu m carbonate-added crackers (ditto) once each alternately on a cross-over de sign with a wash-out period of 3d between the regimens. The study also incl uded controls receiving neither cracker. The degree of intestinal absorptio n of calcium from coral-added crackers and that from calcium carbonate-adde d crackers was evaluated in terms of increment in urinary calcium excretion per dL of glomerular filtrate (GF) (difference between coral calcium and c alcium carbonate) and increase in urinary calcium excretion per milligram c reatinine (difference from control value). The increment in urinary calcium excretion per dL of GF during the latter half of the observation period af ter the ingestion of coral-added crackers was significantly greater than th at during the latter half of the observation period after ingestion of calc ium carbonate-added crackers (p = 0.039, paired t-test). A significant diff erence (from control value) in the increase of urinary calcium excretion pe r milligram creatinine was also observed (p = 0.0008). The present data, th ough from a relatively few study subjects, suggest that the calcium of cora l origin is better absorbed from the intestine than calcium of calcium carb onate origin on the average.