Dietary fluoride intake for fully formula-fed infants in New Zealand: impact of formula and water fluoride

Objective: A survey of the fluoride content of infant and toddler formulae available on the New Zealand market was conducted. Results were used to estimate the dietary fluoride intake for a fully formula-fed infant. Methods: Infant and toddler formulae were prepared according to manufacturers' instructions with fluoride-free water and analyzed for fluoride by a modification of the microdiffusion method of Taves. A proportion of samples were reanalyzed after reconstitution with water at fluoride concentrations of 0.7 and 1.0 mg/L. A stochastic model was used to estimate dietary fluoride intake. Results: The mean fluoride content of prepared infant formulae was 0.069 mg/L. When formulae were prepared with water of differing fluoride concentrations, the fluoride concentration was found to be a simple linear function of water fluoride concentration. Estimates of dietary fluoride intake for infants consuming formulae prepared with fluoride-free water were well below the upper level of intake (UL) for New Zealand and Australia (0.7 mg/day). At water fluoride concentrations of 0.7 and 1.0 mg/L the UL would be exceeded 30 and 93 percent of the time, respectively. Conclusions: The fluoride content of water used to reconstitute infant formulae has a greater impact on fluoride intake of fully formula-fed infants than the fluoride content of the powdered infant formulae. Infants fully formula-fed on formulae prepared with optimally fluoridated water (0.7-1.0 mg/L) have a high probability of exceeding the UL for fluoride and are at increased risk of dental fluorosis.