Scientific Documents

Opinion of the Scientific Panel on Dietetic Products, Nutrition and Allergies (NDA) on a request from the Commission related to the Tolerable Upper Intake Level of Fluoride

Summary (32 KB)

Opinion (347 KB)

Summary

Fluoride is not essential for human growth and development but is beneficial in the prevention of dental caries (tooth decay) when ingested in amounts of about 0.05 mg/kg body weight per day and when applied topically with dental products such as toothpaste. Dental enamel which contains fluoride is less likely to develop caries, because of greater resistance to ingested acids or to acids generated from ingested sugars by the oral bacteria. In addition, fluoride inhibits sugar metabolism by oral bacteria.

Fluoride content of the body is not under physiological control. Absorbed fluoride is partly retained in bone and partly excreted, predominantly via the kidney. In infants retention in bone can be as high as 90% of the absorbed amount, whereas in adults retention is 50% or less. Fluoride is also incorporated into dental enamel during tooth formation.

Excessive intake of fluoride during enamel maturation before tooth eruption from birth to eight years of age, when enamel formation is complete, can lead to reduced mineral content of enamel and to dental fluorosis of deciduous but predominantly of permanent teeth. The incidence and severity of dental fluorosis is dose-dependent. Mild dental fluorosis is not readily apparent and is associated with increased resistance to caries. The Panel considered moderate dental fluorosis, which is characterised by staining and minute pitting of teeth, to be an adverse effect. On the basis that the prevalence of moderate dental fluorosis of permanent teeth is less than 5% in populations ingesting 0.08-0.12 mg fluoride/kg body weight/day, the Panel considered that the upper level (UL) for fluoride is 0.1 mg fluoride/kg/day in children aged 1-8 years. This is equivalent to 1.5 and 2.5 mg fluoride per day in children aged 1-3 years and 4-8 years, respectively.

Fluoride accretion in bone increases bone density but excessive long term intake reduces bone strength and increases risk of fracture and skeletal fluorosis (stiffness of joints, skeletal deformities). Studies with therapeutic oral administration of fluoride in amounts of 0.6 mg/kg body weight/day in postmenopausal women over several years increased the risk for non-vertebral bone fractures significantly. The Panel applied an uncertainty factor of 5 to derive an UL of 0.12 mg/kg body weight/day. This is equivalent to an UL of 5 mg/day in children aged 9-14 years and 7 mg/day for age 15 years and older, including pregnant and lactating women.

The UL for fluoride applies to intake from water, beverages, foodstuffs, including fluoridated salt, dental health products and fluoride tablets for caries prevention.

Children aged 1-8 years have fluoride intakes from food and water well below the UL provided the fluoride content of their drinking water is not higher than 1.0 mg/L. An increase in the prevalence of mild dental fluorosis observed in some countries has been attributed to the inappropriate use of dental care products, particularly of fluoridated toothpaste.

The Panel did not establish an UL for infants. Breast-fed infants have very low fluoride intakes from human milk (2-40 mg/day) and are not at risk of developing enamel fluorosis even when given fluoride supplements of 0.25 mg/day. The Panel notes that the Scientific Committee on Food has recommended a maximum fluoride level of 0.6-0.7 mg/L in infant formula and follow on formula, equivalent to an intake of about 0.1 mg/kg body weight per day in infants during the first six months of life (body weight 5 kg). For powdered formula, this maximum will be exceeded if water containing more than 0.7 mg/L is used for its preparation.

For children older than eight years and adults the probability of exceeding the UL of 5/7 mg fluoride/day on a normal diet is generally estimated to be low. However, consumption of water with a high fluoride content, e.g. more than 2-3 mg/L, predisposes to exceeding the UL.