No one knows how many Australian teenagers turn to their parents one day and announce that- like Lisa from The Simpsons they’re now vegetarian. But the guess is that it’s no rare event – especially among girls. But in the US they’ve crunched some numbers and, based on interviews with 9000 parents, the Centers for Disease Control and Prevention estimate that around one in 200 American teenagers has taken a pledge to veg. Anecdotally, teenage vegetarianism seems to be an increasing trend, often driven by animal welfare concerns and often sparked by animal slaughter videos on YouTube, The Washington Post reported last week, though researchers say there’s not enough evidence to back this up.

In terms of hard figures, there’s less to go on in Australia -although a 1998 South Australian study suggested that around eight to 10 per cent of 16 to 18 year-olds avoided red meat and poultry. But most dietitians will tell you it’s not uncommon – one of them is Accredited Practising Dietitian Tara Diversi who says there are some questions parents should ask their teenager before they simply remove the meat from the plate.

“One of the most important things is to understand why a teenager wants to eat a vegetarian diet – because often it can mask an eating disorder. You need to ask them why they don’t want to eat meat,” she says.”If their reason is that red meat is ‘fattening’, it’s worth pointing out that a healthy diet, including weight loss diets, is a balance of a variety of foods and no one food can make you fat,” she says. But if they still insist on avoiding meat, it’s important to help them fill the nutritional gap with other sources of protein, iron and zinc such as nuts and legumes, she adds. “But if they say they’re also avoiding carbohydrates, sweets and takeaway food – and they’re starting to lose weight – that’s when the red flag should go up because it may mean they’re developing an eating disorder,” Diversi points out.

While it’s true that vegetarians have a lower incidence of heart disease and bowel cancer, a vegetarian diet isn’t a healthy diet if it doesn’t contain the right nutrients, she says – and this is especially important for teenagers whose bodies are still developing and have a high demand for nutrients.

“Vegetarians who depend on eating a lot of cheese for protein, for instance, will miss out on iron and zinc. Some people think they can get enough protein from protein powder – but it’s based on whey (a dairy product) so that doesn’t provide iron and zinc either. It’s very important for parents to get themselves – and their teenager – educated about eating a healthy vegetarian diet,” says Diversi, especially if their teenager wants to follow a vegan diet.

“A teenager might seem to be quite healthy just eating the normal family meals, but without the meat, but the deficiencies in their diet can take time to show up – a teenager who’s been existing on pasta and cheese since year 9, for instance, might start complaining that she can’t concentrate in year 11.”

Diversi’s advice is for the family to consult an Accredited Practising Dietitian or invest in a good vegetarian cook book that also explains how to get the right nutrients. She recommends The Essential Vegetarian CookBook edited by Rachel Carter (Whitecap Books).

“In some cases teenagers can see that their family’s diet isn’t healthy so they decide to eat a vegetarian diet because they think it’s the best way to eat healthily,” she points out. “But they don’t realise that it doesn’t have to be all or nothing – you can have a healthy diet that includes meat.”

The decision to avoid meat doesn’t always last but while it does, different parents take different tacks – one parent I know simply took the view that kids should eat what was put in front of them and offered no vegetarian options.

Others are prepared to support their teenager and adapt family meals. This doesn’t always have to mean cooking separate meals – with many flexible dishes like curries and pasta sauces, it’s possible to produce two versions of the same dish by sauteeing onions and other vegetables all in the same saucepan, then dividing the mix into two separate saucepans, adding meat to one and legumes, nuts or tofu to the other. And it goes without saying that involving teenagers in the choosing and making of healthy vegetarian food is essential.