Fluoride helps prevent cavities and reduce tooth decay, and helps strengthen bones.

How Much: Recommended dietary intake = 4 milligrams (mg) for men; 3 mg for women.

Too Much: Tolerable upper limit (UL) = 10 mg daily.

Too Little: Bone fractures and tooth decay.

Foods: Fluoridated water, tea, and canned salmon and sardines (with bones).

Interactions: Calcium supplements and calcium- and aluminum-containing antacids.

Research Note: Fluoride does not prevent osteoporosis. Fluoride presents safety concerns related to joint pain and stress fractures from taking extremely high doses.