A research team led by Dr Graham Chadwick in the School of Dentistry have investigated whether the method of cooking a popular vegetarian dish, Ratatouille, would have any impact on the acidity of the food, and therefore the potential for contributing to dental erosion.

Their research found that, however it is cooked, ratatouille is acidic. But, oven-roasting significantly increases the acidity compared to the more traditional stewed version of the dish, to the point where it is as acidic as some carbonated drinks.

Dr Chadwick said, The acidity of ratatouille prepared by oven-roasting is the same as that of some carbonated drinks that, when consumed in excess, are believed to contribute to the development of dental erosion.

The finding that cooking method has an impact on the acidity of food is an interesting and useful tool for dentists when advising patients on ways to reduce their chances of dental erosion.

The Dundee team ™s research was based on reports that people on a vegetarian diet may be more at risk from dental erosion because such a large quantity of the foods they eat, such as fruits and vegetables, tend to be quite acidic in nature.

Dental erosion is caused by the direct contact of acid with the teeth. The acid destroys tooth tissues and can result in severe destruction, leading to the need for expensive and time-consuming dental treatment.

The Dundee team also investigated whether the cooking method had an impact on the acidities of individual vegetables and fruits. They found the cooking method had no impact on the acidity of tomatoes or onions, but roasting resulted in more acidic aubergines, green peppers and courgettes. Red peppers were more acidic when stewed.

The research is published in the current edition of the European Journal of Prosthodontics and Restorative Dentistry. It is one in a series of research projects being carried out at the University looking into the causes of dental erosion.

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He illustrated how effective the the program could be by saying an 8-year-old who cuts 45 calories a day from his diet would be 20 pounds (9 kg) lighter by the time he or she graduates from high school.

Clinton has lauded the beverage industry for taking a risk with the initiative, but one expert has said vending machines in schools are not a major source of revenue for carbonated soft-drink manufacturers and the effect will be minimal.

The move is expected to affect 87% of the school drinks market but many believe soft drinks are a visible and easy target and other factors are equally responsible for childhood obesity.

The beverage industry has agreed to apply the new limits to 75 percent of the nation's public and private schools before the start of the 2008-09 school year and apply it to all schools a year later.

In future elementary schools will sell only water, small servings of juices with no added sweeteners, and small servings of milk that are fat-free or low-fat.

Middle schools will have the same restrictions while allowing slightly larger portion sizes.

For high schools, at least half of available beverages must be water, zero-calorie and low-calorie drinks.