Second Thoughts about Fluoride
by Dan Fagin.
Scientific American, January 2008, pages 74–81
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KEY
CONCEPTS
• Researchers are intensifying their scrutiny of fluoride, which is added
to most public water systems in the
Some recent studies suggest that overconsumption of fluoride can raise the risks of disorders affecting teeth, bones,
the brain and the thyroid gland.
• A 2006 report by a committee of the National Research Council recommended that the federal government lower
its current limit for fluoride in
drinking water because of health risks to both children and adults
Page 75: Most fluoridated water contains much less fluoride than the EPA limit, but the situation is worrisome
because there is so much uncertainty over how much additional fluoride we ingest from food, beverages and dental
products. What is more, the NRC panel noted that fluoride may also trigger more serious health problems, including
bone cancer and damage to the brain and thyroid gland. Although these effects are still unproved, the panel argued
that they
deserve further study.
Page 75: TOO MUCH OF A GOOD THING: Fluoride is in many foods, beverages and dental products. The ubiquity
of the cavity-fighting chemical can
result in overconsumption, particularly among young
children.
Page 78: Scientific attitudes toward fluoridation may be starting to shift in the country where the
practice began.
Page 79: But enamel fluorosis, except in the severest cases, has no health impact beyond lowered self-esteem: the tooth
marks are unattractive and do not go away (although there are masking treatments). The much more important
question is whether fluoride’s effects extend beyond altering the biochemistry of tooth enamel formation. Says
longtime fluoride researcher Pamela DenBesten of the University of California, San Francisco, School of Dentistry:
“We certainly can see that fluoride impacts the way proteins interact with mineralized tissue, so what effect is it
having elsewhere at the cellular level? Fluoride is very
powerful, and it needs to be treated respectfully.”
Page 80: Clashes over the possible neurological effects of fluoride have been just as intense. Phyllis Mullenix, then
at the
Forsyth Institute in
rats showed that sodium fluoride can accumulate in brain tissue and affect animal behavior. Prenatal exposures,
she reported, correlated with hyperactivity in young rats, especially males, whereas exposures after birth had the
opposite effect, turning female rats into what Mullenix later described as “couch potatoes.” Although her research
was eventually published in Neurotoxicology and Teratology, it was attacked by other scientists who said that her
methodology was flawed and that she had used unrealistically high dosages. Since then, however, a series of
epidemiological studies in
suggested a possible mechanism: the formation of aluminum fluoride complexes—small inorganic molecules that
mimic the structure of phosphates and thus influence enzyme activity in the brain. There is also some evidence that
the
silicofluorides used in water fluoridation may enhance the uptake of lead into
the brain.
Page 80: The NRC committee concluded that fluoride can subtly alter endocrine function, especially in the
thyroid—the gland that produces hormones regulating growth and metabolism. Although researchers do not know
how fluoride consumption can influence the thyroid, the effects appear to be strongly influenced by diet and
genetics. Says John Doull, professor emeritus of pharmacology and toxicology at the University of Kansas Medical
Center, who chaired the NRC committee: “The thyroid changes do worry me. There are some things there that
need to be explored.”
Page 80-81: “What the committee found is that we’ve gone with the status quo regarding fluoride for many
years—for too long, really—and now we need to take a fresh look,” Doull says. “In the scientific community, people
tend to think this is settled. I mean, when the
greatest achievements of the 20th century, that’s a hard hurdle to get over. But when we looked at the studies that
have been done, we found that many of these questions are unsettled and we have much less information than we
should, considering how long this [fluoridation] has been going on. I think that’s why fluoridation is still being
challenged so many
years after it began. In the face of ignorance, controversy is rampant.”
Page 81: Opponents of fluoridation, meanwhile, have been emboldened by the NRC report. “What the committee
did was very, very important, because it’s the first time a truly balanced panel has looked at this and raised
important questions,” says Paul Connett, a chemistry professor at St. Lawrence University and the executive
director of the Fluoride Action Network, one of the most active antifluoridation groups world-wide. “I absolutely
believe it’s a scientific turning point because now everything’s on the table. Fluoride is the most consumed drug in
the
Page 80: A FLUORIDE DIET
The optimal range for daily intake of fluoride—the level that maximizes
protection against tooth decay but minimizes
other risks— is generally considered to be 0.05 to 0.07 milligram for each kilogram of body weight. Consuming
foods
and beverages with large amounts of fluoride can put a diet above this range.
[The article includes a list of foods and beverages with their fluoride content in parts per million, which is specific to the