Fluoride bioavailability - Nutritional and clinical aspects

Dietary fluoride obtained from food and water is efficiently absorbed from both the stomach and small intestine without regulation. A variety of dietary factors have been identified that either decrease or increase fluoride absorption and utilization. About half of absorbed fluoride is quickly taken-up by developing bone and teeth, and the remainder is excreted in the urine. The amount of fluoride excreted in the urine increases as bone growth slows. Nearly all of total body fluoride, which is second among the trace elements only to iron, is found in-the skeleton. Although fluoride's unique role in mineralization provides the basis for its recognition as a beneficial trace element for dental health of humans, a more subtle role of fluoride in the mineralization of bone is also likely to exist. As with other essential trace elements, fluoride's action is biphasic in nature in that toxicity (fluorosis) can occur. Therapeutic effects of fluoride in the treatment of osteoporosis continue to be studied, and recent developments in this area point to a mitogenic role of fluoride in osteoblast cell proliferation. Recognition of fluoride essentiality for human health, rather than just being classified as beneficial, is likely to be forthcoming especially if reduction of a chronic disease is added to the criteria that establish a recommended dietary allowance. (C) 1997 Elsevier Science Inc.