Abstract
The addition of borates to foods is not permitted in Japan. However, agar may contain boron derived from boric acid. In order to study whether or not the bioavailability of agar-bound boron is different from that of free boric acid, rats that had been subjected to a 16hr fasting period were given a 5% (w/v) suspension of agar, a 2% carboxymethylcellulose solution containing boric acid, or a boric acid solution, by oral intubation. For 24hr after the treatment, only water was given to the animals ad libitum, then the rats were killed. The amount of boron excreted in the urine within 24hr was significantly higher in the three treated groups than in the control group that received only distilled water. However, no significant differences were observed among the three boron-treated groups. The difference in the urinary boron content between the boron-treated groups and the control group was equivalent to approximately two-thirds of the administered dose. No significant differences in the boron contents of the feces and the cecum contents were detected among the four groups. Consequently, there appeared to be no difference in gastrointestinal absorption and urinary excretion of boron between boron in agar and free boric acid.
