Calcium intake during childhood and adolescence is essential for lifelong bone health, with nearly 98 per cent of peak bone mass accrued by the age of 18, according to the researchers from Creighton University.

Approximately 45 per cent of this bone mass is accumulated during the teenage years but teenage girls tend to be reluctant to consume dairy foods, the best dietary source of the mineral, owing to concerns about weight gain.

Average calcium intake for girls nine to 13 years old is 69 per cent of the recommended level and only 55 per cent for girls aged 14 to 18, say the researchers in the September issue of the Journal of the American Dietetic Association.

Their pilot study on 59 nine-year-old girls appears to refute the concerns over dairy foods and weight gain however. It found that the girls who followed a calcium-rich diet, supplying at least 1,500mg per day from dairy foods and calcium-fortified foods, did not experience greater increases in body weight or body mass index compared with girls on their usual diet.

The dairy foods included full-fat products, such as ice cream and cheese on pizzas.

The results did not show, as in previous research, a reduction of body fat in the calcium group over the control and the researchers noted that more research is needed to determine the effect of calcium-rich diets on reducing obesity in children and adolescents.

But among the calcium group there was a slight reduction in the percentage of energy coming from fat, as well as significant improvement in their overall nutritional intake during the two-year study - consumption of protein, vitamins A and D, phosphorus, potassium and magnesium, also increased. The control group who maintained their usual diets increased their consumption only of iron and zinc.

"The fact that fat intake increased in both groups but overall nutrition improved much more in the calcium rich group indicates that girls consuming their usual diet increased their intake of less healthful foods,” write the researchers.

Severe calcium deficiencies may prevent children from reaching their potential adult height, and even mild deficiencies over a lifetime can affect bone density and bone loss. This increases risk for osteoporosis, currently the second biggest chronic health problem globally, according to the World Health Organisation.

Furthermore, recent studies suggest that children and adolescents who have bone mass values less than average are at higher risks for childhood fractures.