Fluoride in human saliva after ingestion of aluminium chloride and sodium fluoride or sodium monofluorophosphate

Four fasting adults were given 5 mg of F as NaF or Na₂PO₃F without and with 3.5, 7.1 or 14.2 mg Al as AlCl₃. Each salt combination was administered in 1 ml aqueous solution, and swallowed in a gelatine capsule with 10 ml of water. Samples of paraffin-stimulated whole saliva, collected before and at short intervals over a period of 3 hr after the administration, were analysed for total and ionic F. After ingestion of F without Al, there was a rapid increase in salivary F, with peak levels of about 0.2 ppm attained after approximately 50 min. When F was ingested with Al, the rate of increase of salivary F was depressed, and peak levels were reduced. This effect was slight for 3.5 mg Al, somewhat greater for 7.1 mg, and marked for 14.2 mg. No Al was detected in the saliva by spectrographic analysis. Fluorine given as PO₃F^2? gave a slower rise in salivary F, and lower peak levels in 3 of 5 subjects than NaF, but the response to Al was similar. Only ionic F was detected in whole saliva and in samples of parotid saliva collected after ingestion of PO₃F^2?. It is concluded that Al interferes with gastrointestinal absorption of F by forming poorly absorbable Al-F complexes, and that PO₃F^2? is subjected to hydrolysis prior to absorption of F. The findings suggest that the Al normally present in food and beverages may affect gastrointestinal absorption of F.