Excretion of retained fluoride in man.

In fluoride studies performed in man the excess fluoride excretions in urine and stool over and above the base-line excretions were determined following the discontinuation of fluoride supplements. The fluoride supplements contained either 9.1 mg fluoride as sodium fluoride, given daily for 32 days, or 7.6 mg fluoride as fish protein concentrate (FPC), given daily for 26 days. Following discontinuation of these fluoride supplements the excess fluoride excretions were low and of short duration, in most cases for 6-12 days. Since the fluoride supplements were given for a known period of time, the fluoride retention could be calculated from the fluoride balances, and the excess fluoride excretion corresponded to 9.1% of the retained fluoride given as NaF and to 14.1% of the retained fluoride given as FPC. The excess fluoride was predominantly excreted via the kidney, i.e., 87% of the total excess fluoride excretion was passed in urine and only 13% in stool.