International Lectures

Abstract

Current recommendations on fluoride intake from the Institute of Medicine's National Research Council in the United States are that the "adequate intake" level is 0.01 mg/day for infants up to 6 months old, and for all ages above 6 months it is 0.05 mg F/kg/day. The "adequate intake" level for a 70 kg adult male is 4 mg/day and for a 52.5 kg adult female it is 3 mg/day. These advisory levels have stood for some years now, but there are some problems with their derivation. For one thing, it is not clear just what these levels of intake are meant to be adequate for: presumably it is for caries prevention in children and for healthy bone in adults. The source for these recommendations is also obscure, and there is reason to believe they could partly be based on questionable data. Their history goes back to McClure in 1943, when he estimated that the "average daily diet" for children up to 12 years contained 0.05 mg F/kg body weight/day. A range of 0.05-0.07 mg F/kg body weight/day was quoted as the "optimum level" in 1980, and it has stood as a guideline since then. Related to these Dietary Reference Intakes is the maximum permissible level of fluoride in drinking waters, currently set at 4.0 mg/L by the Environmental Protection Agency. The reasoning behind this level is that when fluoride is present at a higher concentration the EPA considers that the risk of skeletal problems becomes too high. This figure too has seen some changes over time. Establishing cause-and-effect for fluorosis from dietary fluoride intake is a difficult field of study, though some good information has come from the longitudinal Iowa study of fluoride intake in childhood related to fluorosis development in later childhood. Susceptibility to fluorosis is likely to vary from one individual to another, though this issue has not been studied.