Following a request from the European Commission, the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA) was asked to deliver a scientific opinion on Dietary Reference Values (DRVs) for the European population, including fluoride.
Fluoride has no known essential function in human growth and development and no signs of fluoride deficiency have been identified. Though fluoride is not essential for tooth development, exposure to fluoride leads to incorporation into the hydroxyapatite of the developing tooth enamel and dentin. The resulting fluorohydroxyapatite is more resistant to acids than hydroxyapatite. Thus, teeth which contain fluoroapatite are less likely to develop caries. Apart from incorporation of fluoride into the dentin and enamel of teeth before eruption, dietary fluoride exerts an anticaries effect on erupted teeth through contact with enamel during consumption, excretion into saliva and uptake into biofilms on teeth. In addition, fluoride interferes with the metabolism of oral microbial cells, by directly inhibiting, for example, glycolytic enzymes and cell membrane-associated H+ ATPases in microbial cells after entry of hydrofluoric acid into their cytoplasm.
In bone, the partial substitution of fluoride for hydroxyl groups of apatite alters the mineral structure of the bone. Depending on the dose, fluoride can delay mineralisation. There is evidence from animal studies for a biphasic effect of fluoride on bone strength, with increases in both bone strength and bone fluoride content at moderately high fluoride intake, and a decrease with higher fluoride intake.
Major dietary fluoride sources are water and water-based beverages or foods reconstituted with fluoridated water, tea, marine fish, and fluoridated salt. Fluoride absorption occurs by passive diffusion in both the stomach (20-25 %) and the small intestine. On average 80-90 % of ingested fluoride is absorbed. In adults, up to 50 % of absorbed fluoride is associated with calcified tissues, mainly bone, a small amount reaches soft tissues, and the remainder is excreted, predominantly via the kidney and to a small extent via sweat and faeces.
The role of fluoride in the prevention of caries has been known for many years. In epidemiological studies performed before the 1970s, when fluoride in drinking water was practically the only relevant source of fluoride intake, it was shown that the prevalence of caries was negatively correlated with the fluoride concentration of water. The fluoride concentration at which the caries preventive effect approached its maximum was 1 mg/L, and at that level only 10 % of the population was affected by mild dental fluorosis. The average daily fluoride intake of a child in a community with this “optimal” drinking water fluoride concentration of 1 mg/L was determined as being approximately 0.05 mg fluoride/kg body weight per day from both water and diet.
Since then, many studies have reviewed the efficacy of fluoride in different forms (water, milk, salt, tablets/drops, chewing gum) in preventing dental caries. However, very few of these studies provide information on total dietary fluoride intake, and the outcome measure for caries may have been affected by additional uses of non-dietary fluoride. Therefore, they do not permit a conclusion to be drawn on a dose-response relationship between dietary fluoride intake and caries risk.
The available data on the relationship between fluoride intake or intake deduced from the fluoride content of toenails and bone health did not provide evidence for a beneficial effect of fluoride on bone health.
As fluoride is not an essential nutrient, no Average Requirement for the performance of essential physiological functions can be defined. Because of the beneficial effect of dietary fluoride on the prevention of caries, the Panel considered that the setting of an Adequate Intake (AI) is appropriate and that data on the dose-response relationship between caries incidence and consumption of drinking water with different fluoride concentrations are sufficient to set an AI of 0.05 mg/kg body weight per day. The AI covers fluoride intake from all sources, including non-dietary sources such as toothpaste and other dental hygiene products.
No data are available to define a dose-response relationship between fluoride intake and caries for adults. The Panel considered that the AI for children of 0.05 mg/kg body weight per day can also be applied to adults, including pregnant and lactating women. For pregnant and lactating women the AI is based on the body weight before pregnancy and lactation.
Reliable and representative data on the total fluoride intake of the European population are not available. The available data on fluoride intake are variable but generally at or below 0.05 mg/kg body weight per day.