The amount of fluoride that infants should consume was determined 20 years ago by the Institute of Medicine (IOM) in its Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. The IOM could not determine a "Recommended Dietary Allowance" for fluoride, nor even a less stringent "Estimated Average Requirement." That's because:
"Fluoride has no known essential function in human growth and development [including tooth development] and no signs of fluoride deficiency have been identified," says the European Food Safety Authority (EFSA). "Therefore, no Average Requirement for the performance of essential physiological functions can be defined."
The best the US and Europe could come up with was an "Adequate Intake" (AI) as the reference value for fluoride.
"The AI for fluoride from all sources is set at 0.05 mg/kg/day. This intake range is recommended for all ages greater than 6 months because it is associated with no known unwanted health effects." [IOM p. 302] "No known unwanted health effects" refers to moderate dental fluorosis, the critical adverse effect the IOM used for children, "because the cosmetic effects of the milder forms of enamel fluorosis are not readily apparent." [IOM p. 309]
In other words, if we look into a kid's mouth and can't see any damaged tooth enamel, then that level of fluoride intake must be safe for the entire body. Adverse effects on the infant GI tract or developing brain were not considered.
Imagine if decades ago, teeth were used to gauge the toxicity of nicotine.
Smoking advocacy groups would argue that the critical adverse effect
of a smoking would be yellowing of one's teeth.
Unlike all other age groups, the data used to determine the AI of fluoride for nursing infants was based on actual biological evidence: the amount of fluoride consumed via mother's breast milk arguably the most accurate and reliable data available for determining the appropriate level of fluoride intake for newborns. "The AI is the intake by healthy breast-fed infants as obtained from average human milk nutrient composition and average milk volume." [IOM p. 48] For fluoride, human milk-fed infants receive 0.001 to 0.003 mg/kg/day. [IOM p. 301]
More recent research found that this low level is approximately 0.00030.0016 milligrams of fluoride per kilogram of body weight per day. [EFSA p. 20]
This amount of fluoride nursing infants receive from breast milk daily is extremely low averaging about 0.001 mg (1 microgram) of fluoride per kilogram of body weight. What's more, the fluoride concentration in breast milk is "relatively insensitive to differences in the fluoride concentrations of the mother's drinking water." [IOM p. 305] Even when a mother's fluoride intake is high, levels in her breast milk remain very low.
Breast Milk Promotes Fluoride Elimination
Breast milk does more than protect newborn infants from fluoride intake. It also allows them to excrete the fluoride accumulated while in the womb.
"Exclusively breast-fed infants not receiving a fluoride supplement showed negative fluoride balances up to the age of four months and excreted more fluoride than they ingested." [EFSA p. 13]
"The balance of fluoride can be negative. This occurs when chronic intake is reduced sufficiently to allow plasma fluoride concentrations to fall, which promotes the mobilization of the ion from calcified tissues." [IOM p. 300]
Breast milk also protects nursing infants from lead, another "developmental neurotoxicant" that the EPA's Neurotoxicology Division has found "substantial evidence" (highest category) for being "toxic to the developing mammalian nervous system." Even if a mother's intake is high in lead, her breast milk is very low in lead.
For non-breastfed infants, their fluoride intake depends on the concentration of fluoride in the water used to prepare their formula. "Use of water with 1.0 mg fluoride/liter compared to 0.15 mg/liter increases the fluoride intake of the infant five-fold." [EFSA p. 20]
For formula-fed infants under one year old, if their drinking water is not fluoridated, their cumulative average intake of fluoride is 0.11 mg/kg/day. If their water is fluoridated, it's 0.20 mg/kg/day. [Erdal and Buchanan 2005] That is twice their Tolerable Upper Intake Level of fluoride which the IOM says is 0.10 mg/kg/day.