Fluorine

Small amounts of fluorine are naturally present in water, air, plants and animals. As a result humans are exposed to fluorine through food and drinking water and by breathing air. Fluorine can be found in any kind of food in relatively small quantities. Large quantities of fluorine can be found in tea and shellfish.
Fluorine is essential for the maintenance of solidity of our bones. Fluorine can also protect us from dental decay, if it is applied through toothpaste twice a day. If fluorine is absorbed too frequently, it can cause teeth decay, osteoporosis and harm to kidneys, bones, nerves and muscles.