Both Fluorine (as fluoride in water) and bromine (used in bread processing) are halogens, which compete with iodine receptors in the body, leading to decreased thyroid function, slow metabolism and weight gain. To maximize iodine in the body be sure to limit or eliminate fluoridated water, buy bromine free bread, and eat foods high in iodine like ocean fish, fish oils, sea kelp, dulce, fruits and vegetables.