Just like many of her contemporaries, teenage model Kirsty Ashcroft may not be getting the calcium she needs. Glenda Cooper reports
FIFTEEN-YEAR-OLD Kirsty Ashcroft may see her face on the cover of teen magazines and model for Paul Smith but in some ways she is very ordinary. Ashcroft is like many of her less famous contemporaries - who have just voted her teen magazine Sugar's "Face of 1998" - she hates eating cheese.

Doctors are worried that teenage girls could be putting themselves at risk of the bone-thinning disease osteoporosis by not getting enough calcium. Osteoporosis is a major public-health problem, with 40 per cent of women sustaining an osteoporotic fracture at some time in their lives. Adolescence is a crucial time for bone mineral acquisition but health experts fear the desire to diet means that girls are avoiding calcium- rich foods such as milk because they think they are fattening.

Kirsty gets her calcium from "lots and lots" of yoghurt. She does her best to eat healthily. "My mum is always on at me to eat at least four pieces of fruit a day." But last week a new survey warned that teenage girls are putting their health at risk by skimping on meals, afraid that they are overweight.

More than six out of 10 girls aged 14 to 15 years old say they would like to lose weight, although only 15 per cent weigh too much for their weight and height. On the other hand, boys of the same age have a more realistic attitude. Just over a quarter said they would like to lose weight; just under one in five were overweight.

But the survey, carried out by the Schools Health Education Unit, found that girls are skipping meals to try to lose weight and by the time they reach 15 years old, more than three out of 10 girls are missing breakfast or just have a drink and one in seven does not eat lunch.

"Sometimes I think girls do worry too much about what they look like," says Ashcroft who is 5ft 6in and weighs 8.5st. "I think they look at skinny models in magazines and want to be like them." She says she is lucky to have an agency that does not pressurise her about her weight.

"Girls want to be tall and slim," says Alison Graham of the National Osteoporosis Society. "But what they are not aware of is that dieting can lead to the risk of fragile bones. This is very deforming for the figure, but we are increasingly seeing girls in their twenties with fractures in their spine and they can lose up to a few inches in height.

"It's deforming your body. It's difficult for teenagers to look ahead but we must encourage them that the teenage years are critical for bone development. By the age of 20, you have laid down 97 per cent of your skeleton's bone strength."

A study reported in the British Medical Journal looked at the effect on drinking more milk in adolescence. Researchers from Sheffield asked more than 80 girls aged 12 at four different city schools to drink an extra half-pint of milk a day for 18 months. They found the girls did not put on or lose weight, or grow any faster, but their bone mineral density was "significantly greater" than in a similar group of girls who consumed their usual diet. The researchers concluded that a modest increase in milk consumption could have a "substantial" impact in the incidence in future fractures.

Teenagers need 1000mg of calcium today - two thirds of a pint of milk. But confront your average weight-conscious teen with a pint of milk and the chances are she won't want to drink it. "It is difficult," says Graham. "We are all aware of this. A national survey of school children's diets, conducted by the Department of Health (DoH), showed the average calcium intake of adolescent girls is falling - almost 20 per cent were so low that if they were maintained at this level they were unlikely to be adequate.

"It's difficult because you can't see bones, but we have got to get the message across. One of the ways to do so, nutritionists think, is to point out alternatives to full-fat milk. Low-fat varieties of milk, cheese and yoghurt are as rich in calcium as full-fat varieties".

"If it is a problem, girls should switch to skimmed milk," says Wynnie Chan of the British Nutrition Foundation. "That will do you just as much good. You need about a pint of milk a day in your teenage years to get enough calcium."

Isabel Skypala, head of dietetics at the Royal Brompton Hospital and author of What Are You Eating?, says there are many ingenious ways to get your teen to eat enough calcium. "It's a question of looking," she says. "You can always try things like yoghurt, because they are low fat and easy to eat. Breakfast cereal is also a good idea, because many are fortified with vitamins and minerals like calcium and, of course, you pour milk on top.

"It is difficult, because teenagers skip meals and then they go out and have take-aways, so you have to think about the food that they like to eat.

"People are unaware that bread, particularly fortified bread, has a fair amount of calcium, as does pizza. A pasta dish with cheese is a good source and with all of these it isn't like you are pushing them to eat something calcium-rich and obviously 'good for them'.

"Other good sources of calcium include green vegetables, such as spinach, but you will be hard-pushed to get many teenagers to eat them as they don't come across as terribly exciting."

For odd treats mothers may be relieved to hear that their daughters can get 65mg in a choc ice or 55mg in a hot-cross bun or even 100mg in four fish fingers. "Obviously you wouldn't want them to be living on them," says Dr Skypala, "but they can all contribute to your daily intake."

The other important way for girls to improve bone strength is to exercise -but many are like Ashcroft, who says "I don't really exercise at all. I used to try to go swimming at my local leisure centre, but I don't go that often."

"It is so important to take regular exercise," says Graham. "Girls should particularly try to take exercise that is load bearing on your bones, such as running, jogging or aerobics. The more impact you put on your bones the greater the strength. I cannot emphasise how important it is you get your bones in good shape."