Lacing drinking water with fluoride can wreck your thyroid and lead to weight gain and depression, says a study from Great Britain's University of Kent, which found a correlation between rates of hypothyroidism and levels of fluoride in drinking water.
Researchers studied the numbers of people in England diagnosed with hypothyroidism (underactive thyroid), and found that areas with fluoride levels above 0.7 milligrams per liter of water had at least 30 percent more cases than areas with lower levels. When they compared two areas head-to-head — one that had fluoridated drinking water (West Midlands) and one that did not (Greater Manchester), rates of hypothyroidism in the fluoridated area were twice that of the unfluoridated area.
People with hypothyroidism don't produce enough of the hormones testraiodothyronine (T4) and triiodothyronine (T3), and the deficiency can interfere with many metabolic functions including the ability to use the energy from food efficiently. Symptoms can include weight gain and depression.
Lead author Stephen Peckham says that authorities need to consider reducing fluoride exposure, including removing it from drinking water, and skipping fluoride treatments on teeth and switching to other methods to protect teeth.
Currently, the amount of fluoride in drinking water in the United States recommended by the EPA is 0.7 to 1.2 milligrams per liter of water with 4.0 milligrams per liter as the maximum considered safe.