Stop fluoridation now: new research on fluoride's brain and thyroid toxicity

Townsend Letter for Doctors and Patients, April, 2005 by Gary Null, Martin Feldman

* The mean IQ of 60 children, aged 10 to 12 years, in an area with a high level of fluoride in drinking water was significantly lower (92.27 [ or -] 20.45) than that of 58 children in a low-fluoride area (103.05 [ or -] 13.86). The high-fluoride area also had more children (21.6%) in the retardation or borderline categories of IQ than did the low-fluoride area (3.4%). (21)

* Among 907 children, aged 8 to 13 years, there was a 15 to 19 point decrease in IQ in children living in an area with a high fluoride exposure compared with those in an area with little or no exposure. Exposure to a high level of fluoride may affect intelligence at an early, rapid stage of development in the embryo and infant. (22)

In addition to studies on intelligence, other research on humans has associated fluoride with problems in brain functioning. A study of children who grew up in a coal-burning-pattern high-fluoride area in China found that excessive fluoride intake since early childhood would reduce mental work capacity. (23) A study in Mexico found that while children's IQ scores were not influenced by fluoride exposure, other effects on neuropsychological development were associated with chronic exposure (the main source being tap water.) Urinary fluoride correlated positively with an increase in reaction time, which could affect the attention process, and inversely with low scores in visuospatial organization, which could have an impact on the children's reading and writing abilities. (24) A study of structural fumigation workers found that while occupational exposure to sulfuryl fluoride did not cause any widespread pattern of cognitive deficits, such exposure "may be associated with subclinical effects on the central nervous system, including effects on olfactory and some cognitive functions." (25)

Fluoride's effect on the human brain also extends to the fetus. An examination of 15 therapeutically aborted fetuses in the fifth to eighth month of gestation from a high-fluoride area documented a number of changes in the neurons, undifferentiated neuroblasts and mitochondria. The study concluded that chronic high-fluoride exposure during intrauterine life "may produce certain harmful effects on the developing brain of the fetus." (26)

Another study shows that low concentrations of a variety of salts, including sodium fluoride, significantly reduce the thermodynamic stability of the human prion protein, and thereby may help promote its conversion to a misfolded form of the protein that accumulates in the brain. Prion diseases are fatal neurological disorders that occur in animals and humans. The human versions include Creutzfeld-Jacob disease, Gerstmann-Straussler-Scheinker disease, fatal familial insomnia and kuru. (27)

A number of animal studies also have linked fluoride to neurotoxic effects, such as impaired learning and memory abilities, suppression of spontaneous motor activity and poor performance in motor coordination and maze tests. (28-31) A study by Dr. Phyllis Mullenix and colleagues at Forsyth Dental Center in Boston, published in 1995, evaluated the effects of fluoride on the developing brains of rats, using a computer pattern recognition system to quantify various aspects of the animals'behavior. Prenatal exposure to fluoride was associated with hyperactivity in offspring, and exposure during weaning and adulthood was associated with "cognitive deficits." The severity of the behavioral effects increased directly with plasma fluoride levels and concentrations in specific regions of the brain following fluoride ingestion. The researchers said of their findings: "Of course behaviors per se do not extrapolate [across species], but a generic behavioral pattern disruption as found in this rat study can be indicative of a potential for motor dysfunction, IQ deficits and/or learning disabilities in humans." (32,33)