Fluoride content of infant formulas: soy-based formulas as a potential factor in dental fluorosis.

Abstract

Recent reports of art increased prevalence of dental fluorosis in fluoridated and nonfluoridated communities have led to a reassessment of the amount offluoride (F) being ingested infants and young children. Manufacturers of milk-based formulas have taken steps to reduce the F concentration to negligible levels. Reduction of F concentration in soy-based formulas is more difficult because ofF binding to phytate and tricalcium phosphate. This study assessed the F content of 3 milk-based and 4 soy-based infant formulas. Three types of preparations in each brand were tested: ready-to-feed, liquid concentrate, and powdered concentrate. Concentrates were diluted according to the manufacturers’ recommendations with water containing various concentrations of F. The ionic F was measured using an ion-specific electrode. Acid-diffusable F was measured after separation by the Taves method. Soy-based formulas contained higher levels ofF than their milk-based counterparts. In the case of ready-to-feed and liquid preparations the differences were statistically significant. The mean F concentrations for soy-based products were: ready-to-feed, 0.30 mg/l; liquid concentrate diluted with deionized water, 0.24 m g/l ; and powdered concentrate dilu ted with deionized water, 0.08 mg/l. Both soy-based ready-to-feed and diluted liquid concentrate formulas provide daily F dosages which, in combination with supplemental dietary F (0.25 rag~day), exceed the currently defined norms for optimum daily F intake. Recent reports have described an increased prevalence of dental fluorosis in children’s teeth in both fluoridated and nonfluoridated communities (Aasenden and Peebles 1974; Forsman 1977; Messer and Walton 1980; Leverett 1982,1986) greater than that reported in the early studies of Dean et al. (1942). Soparkar and DePaola (1985) reported finding an unexpectedly high number of school children with dental fluorosis residing in nonfluoridated areas of Massachusetts. Leverett and Levy (1983) reported similar findings in children both fluoridated and nonfluoridated communities in an earlier study. Horowitz et al. (1984) speculated that the increased prevalence of dental fluorosis in younger children could be related to infant formulas and other foodstuffs processed with fluoridated water. Studies have indicated that in several species, including humans, a daily fluoride (F) intake of 0.1 mg/kg body weight during the period of enamel calcification is sufficient to cause mild dental fluorosis (Forsman 1977; Suttie et al. 1972). It should be emphasized that the levels of fluorosis reported by these investigators are in the very mild and mild categories described by Dean et alo (1942) and are, for the most part, not discernable by the layman.