Two new studies of community water fluoridation have shown that, while there may be small benefits to bone, the effects of high fluoride consumption on children's teeth are still cause for concern.

In the first study, researchers in Oregon collected data on fluoridated water exposure and risk factors for osteoporosis from more than 7000 women. Beginning in 1986, the women underwent bone mineral testing of the lumbar (lower) spine, proximal femur (top of the thigh bone) and radius (forearm).

Among 3218 women with continuous exposure to fluoridated water, bone mineral density (BMD) averaged 2.6 per cent higher at the femoral neck, 2.5 per cent higher at the lumbar spine and 1.9 per cent lower at the distal radius (wrist) than in women not exposed. Fractures occurred in both groups and, while women with continuous fluoride exposure had slightly fewer hip and spine fractures, they had more wrist fractures than non exposed women.

Put into perspective, the small gains associated with continuous fluoride exposure in this study are similar to those seen in women who have increased their dietary calcium and engage in regular weight bearing exercise (without the still unknown risks of long term fluoride exposure).

While the most positive conclusion that can be drawn from the data is that continuous fluoride doesn't appear to increase the risk of fractures, neither does it appear to present significant benefits (BMJ, 2000; 321: 860-4).

In a second study, UK researchers took a wider look at the safety and efficacy of fluoridated drinking water. They took into account the results of more than 200 studies many of which, the researchers admit, were of low to moderate quality.

The results of the review were something of a blow to fluoride supporters, since the overall reduction in dental caries was smaller than previously reported. Among the potential adverse effects of water fluoridation, mottled teeth (fluorosis) remained the most prevalent, and the higher the concentration of fluoride in the water, the greater the risk of fluorosis (BMJ, 2000; 321: 855-9).