A diet to keep you smiling

Dentists could soon be prescribing old-fashioned British fry-ups or salads dressed in olive oil to fight tooth decay. Whatever the problems fats and oils may cause with weight-loss, research has shown that they can strengthen teeth - just like fluoride - by protecting against demineralisation.

Specialists divide foods into those that protect teeth, those that cause cavities and others that are neutral.

Tooth fairies

Olive oil

Teeth exposed to olive oil show significantly less demineralisation and cavityformation. Indeed, olive oil is proving so effective at keeping teeth strong, it has been incorporated into a toothpaste, Airlift, sold in Boots.

"Studies have found that olive oil works internally and externally to protect teeth," says Dr Maria Rodriguez, professor of dentistry at the University of Madrid. "Olive oil substantially lowers acidity in the mouth - which can lead to cavities - and attaches to bacteria, washing them away. In addition, it contains high levels of oleic acid and vitamin A, which promote tooth mineralisation."

Nuts and seeds

Brazil nuts, walnuts and pumpkin seeds are rich in oils that protect teeth by fighting acidity in the mouth. "Most nuts, except for the sweeter varieties like cashews, are good for the mouth, gums and teeth," explains Dr Rodriguez.

If you've just had a sweet snack or drink, eating a handful of nuts can protect teeth, by neutralising any acid.

Oily fish

Oily fish such as tuna and mackerel can lower mouth acid levels for up to three hours. Evidence is emerging that fish oils line the teeth with a coating of fat, preventing bacteria from sticking to them and causing decay.

Cheese

Cheese acts in a similar way to oily fish. Eating a portion of cheese is an ideal way of protecting teeth from the toothweakening effects of sweet desserts.

Tooth Enemies

Milk Chocolate

Chocolate, confectionery and sweet fizzy drinks all create an oral environment that weakens teeth. Sugar causes an almost instant increase in acidity that can last for two hours or more. This strips away minerals, allowing bacteria to multiply. Either limit consumption of these foods or eat cavity-fighting foods immediately after.

Low fat crisps

"Eating low-fat crisps or rice crackers as snacks is as bad as eating sugary foods regularly," says Dr Rodriguez. "Crisps acidify the mouth very quickly. Fat neutralises acid but, in low-fat varieties, it is taken out. Fatty crisps are better, but not necessarily for other aspects of health."

White bread

White bread is high in refined carbohydrate and low in fat. This means it turns to sugar and quickly acidifies the mouth, leaving teeth prone to decay. "'White bread alone is cavity-forming. However, if you eat it with butter or something fatty, the effects will be neutralised," says Rodriguez.

Neutral Foods

Vegetables

Tea and coffee acidify the mouth. Add sugar and plaque-forming bacteria will thrive and weaken teeth. The toothweakening effect of just one cup of tea can last for two hours.

Meat

All meats neutralise mouth acid. Plaqueforming bacteria cannot multiply and anti-bacterial enzymes in saliva can function at their best.

Grapes

While apples, strawberries and bananas have little impact on overall mouth acidity, very sweet fruit, such as grapes and mangoes, make the mouth acid. Combining grapes or raisins with nuts can reduce or even neutralise their effect.

Vegetables

Broccoli, carrots, spinach, peppers and other vegetables encourage a healthy neutral pH. Not only do vegetables help "lock in" tooth minerals, they contain anti-bacterial substances that help kill microbes.

How best to balance your diet

Diets that are low in fat but high in carbohydrates strip minerals from teeth because the carbs turn to sugar and acid. But if you combine them with fat or protein you will not damage your teeth since the fat helps protect tooth enamel. The best diet for teeth is one that contains moderate levels of carbohydrates and sugar and plenty of oils and protein. So that's olive oil, fish, cheese and nuts, plus neutral foods such as vegetables or lean meat.