A recent review identifies the molecular mechanisms by which fluoride inhibits sodium iodide symporter expression and functionality, which in turn contributes to impaired iodide absorption, diminished iodide-concentrating ability, and iodine deficiency disorders. Overall, studies suggest that fluoride exposure directly affects the bio-availability of iodine in humans.
This is particularly important for New Zealanders, as NZ soil is deficient in iodine, and over 50% of the population is supplied with fluoridated water. It is well known that New Zealanders are commonly deficient in iodine, and iodine is now routinely given to pregnant women. Considering the importance of iodine on health, compulsorily medicating the population (as the Supreme Court has ruled it is) with a toxic substance that reduces this vital nutrient is not just unbelievably irresponsible, it is verging on criminal.
Evidence from epidemiological studies also suggest that the combination of iodine deficiency and fluoride exposure result in higher risk of developmental disorders, including impaired cognitive function in children. One particular study concluded that excessive fluoride exposure and iodine deficiency interact synergistically to induce brain damage.
Hypothyroidism resulting from insufficient iodine intake and/or absorption, can occur at any stage of life, but the most devastating consequences of iodine deficiency take place during foetal development and childhood, with stillbirth, miscarriages, poor growth, and cognitive impairment. Iodine deficiency remains a major public health problem worldwide and the world’s greatest single cause of preventable brain damage
In 2002, the Scientific Committee on Food, the main committee providing the European Commission with scientific advice on food safety, reported that dietary iodine absorption and incorporation is reduced by fluoride in food and water.
These findings support the findings of epidemiological studies.
A recent cross-sectional study conducted in Canada found that urinary iodine concentrations were lower in fluoridated than non-fluoridated communities. Moreover, iodine deficient individuals were found to have higher urinary fluoride concentrations compared with the non-iodine deficient group.
Similarly, a recent all Ireland study that measured iodine status in adolescent girls throughout the island of Ireland, found that the percentage of adolescent girls with moderate to severe iodine deficiency was 2–4-fold higher in the Republic of Ireland (84% fluoridated) compared to nonfluoridated Northern Ireland.
A 2014 study by Peckham et al  found “that higher levels of fluoride in drinking water provide a useful contribution for predicting prevalence of hypothyroidism. We found that practices located in the West Midlands (a wholly fluoridated area) are nearly twice as likely to report high hypothyroidism prevalence in comparison to Greater Manchester (non-fluoridated area).”
The researchers concluded “In many areas of the world, hypothyroidism is a major health concern and in addition to other factors—such as iodine deficiency—fluoride exposure should be considered as a contributing factor. The findings of the study raise particular concerns about the validity of community fluoridation as a safe public health measure.”
1. D T Waugh “Fluoride Exposure Induces Inhibition of Sodium/Iodide Symporter (NIS) Contributing to Impaired Iodine Absorption and Iodine Deficiency: Molecular Mechanisms of Inhibition and Implications for Public Health” International Journal of Environmental Research and Public Health 2019, 16(6), 1086.
2. Peckham, Lowery & Spencer “Are fluoride levels in drinking water associated with hypothyroidism prevalence in England? A large observational study of GP practice data and fluoride levels in drinking water” Journal of Epidemiology and Community Health 2015, 69(7):619-24.