Every single day, your body takes in fluoride and loses fluoride. The way you take in fluoride is through foods you eat and water. The way you lose fluoride is through demineralization of your teeh when acids caused by plaque bacteria and sugars in your mouth attack tooth enamel. You can "put fluoride back" (as well as calcium and phosphate) into your tooth’s enamel layer by eating healthy foods and drinking fluoridated water. Another way to get more flouride is through fluoride treatments at your dentist's office.