Fluoride Action Network



"“The conclusion from the available studies is that sufficient fluoride exposure appears to bring about increases in blood glucose or impaired glucose tolerance in some individuals and to increase the severity of some types of diabetes." (National Research Council, 2006)


Diabetes mellitus is a potentially life-threatening disease, in which the body fails to properly regulate blood sugar levels. Diabetes mellitus affects nearly 26 million people in the U.S. alone—with 7 million of these remaining undiagnosed, and therefore untreated.

Fluoride has been shown to increase blood glucose levels and impair glucose tolerance, likely by inhibiting insulin production or secretion. Impaired glucose tolerance, often a precursor to type 2 diabetes, has been found to occur in humans with fluoride intakes of only 0.07-0.4 mg/kg/day—a dose that can be reached in areas of “optimally” fluoridated water. Current fluoride intake, therefore, may contribute or exacerbate some types of diabetes. According to the National Research Council (2006), “any role of fluoride exposure in the development of impaired glucose metabolism or diabetes is potentially significant.”

Diabetics also generally drink more water than nondiabetics, and thus can consume substantially more fluoride from water and other beverages on a daily basis. Diabetics are therefore considered to be a “sensitive subpopulation” with regard to fluoride exposure, and may suffer disproportionately from fluoride’s adverse effects. 

Increased Blood Glucose

As carbohydrates are consumed and digested, blood glucose levels increase. If the body is not able to regulate the amount of glucose in the blood, as occurs in diabetes mellitus, chronic elevated blood sugar (hyperglycemia) can lead to serious complications. These may include damage to the kidneys, brain and nervous system, cardiovascular system, retina, legs and feet, etc. Human and animal studies have found that excessive fluoride consumption leads to increased serum fluoride levels, with a concomitant increase in serum glucose levels. See studies.

Inhibition of Insulin and Glucose Intolerance

Insulin is a hormone produced by the pancreas that is responsible for maintaining appropriate levels of glucose in the blood. Insulin allows the body’s cells to take up glucose from the blood, and either use it as an energy source or store it as glycogen. Blood glucose levels in diabetics are not properly regulated, either because the pancreas does not produce adequate amounts of insulin (i.e., type 1 diabetes mellitus), or because the body’s cells have become less responsive to insulin that is produced (“insulin resistance”; i.e., type 2 diabetes mellitus).

Glucose intolerance (or impaired glucose tolerance) refers to the body’s inability to properly clear glucose from the bloodstream. A person is said to have impaired glucose tolerance when a glucose tolerance test at two hours shows blood glucose levels that are elevated, but less than would qualify for type 2 diabetes mellitus. The primary mechanism responsible for fluoride-induced impairments in glucose tolerance appears to involve the inhibition of insulin secretion from pancreatic cells. Studies on both animals and humans have revealed a transient inhibition of insulin secretion following fluoride ingestion, resulting in hyperglycemia (elevated blood sugar). Fluoride may also lead to increased insulin resistance, or decreased insulin sensitivity, thus contributing to glucose intolerance. See studies

Diabetics as a “Sensitive Subpopulation” 

In response to elevated blood sugar and increased frequency of urination, diabetics (especially those with untreated or poorly controlled diabetes) drink significantly more water than nondiabetics, and may consume more fluoride on a daily basis from water and other beverages. Furthermore, research has found that diabetics have a reduced capacity to clear fluoride from the body, (Hanhijarvi 1975), which may be a result of the kidney damage (nephropathy) that can accompanies diabetes. As noted in one review, “subjects with nephropathic diabetes can exhibit a polydipsia-polyurea syndrome that results in increased intake of fluoride, along with greater-than-normal retention of a given fluoride dosage.” (Marier 1977).

The increased exposure and retention of fluoride places diabetics at increased risk for fluoride-related toxicity. In animals with type-1 diabetes, for example, fluoride has been found to increase vascular contractions (Hattori et al, 2000), possibly contributing to an already elevated risk for cardiovascular disease in diabetics.

Diabetes Insipidus

As with diabetes mellitus, those with uncontrolled diabetes insipidus drink excessive amounts of water. Researchers have observed moderate and severe dental fluorosis in people with hereditary diabetes insipidus—a result of drinking “optimally” fluoridated water (1 ppm) during tooth development. Thus far, no studies have been conducted to determine if diabetics have an elevated risk for dental fluorosis.

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