Sugar intake should be cut to just five teaspoons a day to reduce tooth decay, British scientists warned on Tuesday while presenting a study of the effects of sugar on our oral health.

Since 1990, the World Health Organisation (WHO) has recommended that intake of "free sugars" should be less than 10 percent of total energy intake. Free sugars are sugars that are added to foods by the manufacturer, cook, or consumer; plus those naturally present in honey, syrups, fruit juices and fruit concentrates.

The Newcastle University study, published today in the Journal of Dental Research recognizes the benefit of this threshold, by showing that when less than 10 percent of total calories in the diet is made up of free sugars there are much lower levels of tooth decay.

The research findings suggest that halving this threshold for sugars to less than 5 percent of calories, around five teaspoons a day, would bring further benefits, minimizing the risk of dental cavities throughout life.

"In the past, judgments on recommended levels of free sugars intake were made based on levels associated with an average of three or fewer decayed teeth in 12-year-olds," Professor Paula Moynihan said.

"Part of the problem is that sugary foods and drinks are now staples in many people's diet in industrialized countries, whereas once they were an occasional treat for a birthday or Christmas. We need to reverse this trend," she added.