Ellen Phiddian
Cosmos science journalist
Fluoride in drinking water may not have the big impact it used to, according to a Cochrane review.
Cochrane reviews, run by the international not-for-profit Cochrane Collaboration, produce some of the most highly trusted reviews in medical science.
This review finds that following the widespread use of fluoride toothpaste, communities have enjoyed smaller benefits from fluoride in tap water.
“The evidence suggests that water fluoridation may slightly reduce tooth decay in children,” says co-author Dr Lucy O’Malley, from the University of Manchester, UK.
“Given that the benefit has reduced over time, before introducing a new fluoridation scheme, careful thought needs to be given to costs, acceptability, feasibility and ongoing monitoring.”
This review emphasises that the researchers only have limited confidence in their findings, since all of the 157 studies they examined weren’t randomised.
“When interpreting the evidence, it is important to think about the wider context and how society and health have changed over time,” says co-author Professor Anne-Marie Glenny, also from the University of Manchester.
“Most of the studies on water fluoridation are over 50 years old, before the availability of fluoride toothpaste. Contemporary studies give us a more relevant picture of what the benefits are now.”
Fluoride naturally occurs in water in small amounts. It helps to strengthen teeth through a process called remineralisation.
Different jurisdictions have been adding fluoride to tap water since the 1940s. Until the introduction of easy-to-access fluoride toothpaste in the mid-1970s, there was comprehensive evidence that children growing up in areas with fluoride in tap water had fewer cavities than children growing up in non-fluoride areas.
This study examined 157 other studies on fluoride in tap water, including those conducted both before and after 1975. The studies all focussed on children.
The results suggest that, after 1975, children’s baby and adult teeth were marginally improved by the introduction of fluoride to tap water, but the effect was very small.
The researchers also looked for any adverse effects of fluoride in drinking water, and couldn’t find any evidence – with a high level of certainty.
“Contemporary evidence using different research methodologies suggest that the benefits of fluoridating water have declined in recent decades,” says co-author Professor Tanya Walsh, from the University of Manchester.
“Whilst water fluoridation can lead to small improvements in oral health, it does not address the underlying issues such as high sugar consumption and inadequate oral health behaviours,” says co-author Professor Janet Clarkson, from the University of Dundee, UK.
“It is likely that any oral health preventive programme needs to take a multi-faceted, multi-agency approach.”
