Dentists warn that children who are encouraged to drink large amounts of fruit juice as part of their “five a day” could be damaging their teeth.

Specialists are concerned that health- conscious parents who regularly give their children juices and smoothies bursting with fruit could be doing long-term damage.

Dr. Kathy Harley, dean of the dental faculty at the Royal College of Surgeons in UK, warned that half of 5-year-olds had signs of wear to their tooth enamel.

She has called on schools to offer milk or water to pupils during breaks instead of fruit juice, which has a high acid content.

Dental erosion, which is irreversible, is caused by acid attacking the surface of teeth – and citrus fruit juices in particular are very acidic.

While fruit juices contain a range of vitamins that are good for your health, they are also often high in natural sugars, which cause tooth decay.

Kathy Harley suggested parents should give their children fruit juice as a treat once a week, for example on Saturdays.

It suggests people drink the juice with a meal as this can help to reduce damage to the teeth.

Drinking more than one glass of juice a day does not count as more than one portion of fruit, as it does not contain the fibre found in the whole fruit.

Juicing or blending fruit releases the sugars inside and is worse for the teeth if drunk frequently.

Dentists warn that children who are encouraged to drink large amounts of fruit juice as part of their “five a day” could be damaging their teeth

Some researchers also say drinking juice slowly can cause more damage to teeth.

Dentists have previously warned that, while tooth decay is less common as more children and adults brush their teeth regularly than in the past, dental erosion is a growing problem due to acidic drinks.

Research published last year by King’s College London Dental Institute, based on a study of 1,000 people aged between 18 and 30, suggested eating an apple could be worse for teeth than drinking a fizzy drink because of the acid it contains.

Experts recommend people continue to eat fruit but drink water afterwards to wash away the acid or eat something containing calcium, such as cheese, which neutralizes acid.

Damien Walmsley, an adviser to the British Dental Association said: “If you are having fruit, keep it to meal times. That [may] go against the [recommendation of] five portions of fruit and vegetables a day, but it is not a good idea snacking on it because of the continual drip, drip on to the tooth.”