Dr Sarah Raphael, specialist paediatric dentist and Australian Dental Association spokeswoman. Dentists say some of the biggest culprits are highly processed, sugary foods and drinks, and as families gear up for the new school year, they are urging them to cut the empty calories. A Fairfax Media analysis found that in extreme cases a school lunch box consisting of five basic items can easily contain more than 160 grams of sugar, or 40 teaspoons. Australian adults and children should consume no more than 51 grams in free sugars a day, according to World Health Organisation guidelines, and halving this amount can lead to extra health benefits. The term "free sugars" extends the definition of added sugars to include sugars naturally present in honey, fruit juice and fruit juice concentrates.

Dr Raphael said apart from obesity and weight-related health problems such as type 2 diabetes, consuming too much sugar was linked to tooth decay because the bacteria that breaks down food and drinks in the mouth produced acids that erode the tooth enamel. She said parents should be extra wary of sweet sticky food that can get stuck in the grooves of the teeth and always provide water so that sugars and acids can be washed away. "We're seeing kids from 18 months with decay and the peak age range for paediatric dentists treating children under general anaesthetic because of decay would be three to six years of age," she said. "Decay affects the way children smile, socialise, eat and even speak properly, and these kids are going to form speech patterns that are more awkward." About one-third of NSW children aged five to 10 have decay in their baby teeth and one-fifth of children aged six to 14 have decay in their permanent teeth, the National Child Oral Health Study 2012-14 found.

More than 5500 children aged up to 14 were hospitalised for tooth decay-related operations in 2015-16, up 48 per cent on the figure a decade and a half ago, NSW Health statistics reveal. Slash the sugar by 80% A Fairfax Media analysis of lunch boxes found healthy, low-sugar swaps could drastically reduce the total sugar content by 80 per cent.

A lunch box consisting of a sandwich with Cottee's Strawberry Jam; All Natural Bakery Yoghurt, Peach and Mango Oat Slice; Gippsland Toffee and Honeycomb Twist Yoghurt; Angas Park Dried Apples; and Coca-Cola bottle contained a 161 grams of sugar. Swapping each item for a wholegrain sandwich with Vegemite; carrot sticks with a beetroot dip; Chobani Plain Yoghurt; fresh apple; and Inside Out Spiced Vanilla Almond Milk reduced the overall sugar content by 82 per cent to 29 grams of sugar. The sugar could be further reduced by switching the drink for a bottle of water, which nutritionists recommend.

'It's just too much' Professor Clare Collins, a nutrition expert at the University of Newcastle, said she would go one step further and eliminate all nut and muesli bars. "You don't need to have any packaged snacks at all, and I know muesli bars are convenient, but keep them for an emergency, make it the exception," she said. "People also think orange juice is okay, but sometimes one bottle can contain four to six oranges' worth of sugar, and that's just too much." She encouraged parents to drop a small bag of cherry tomatoes, snack cucumbers or baby carrots into the lunch box, as well as a can of baked beans or tuna.

Lindy Sank, a dietitian at the Sydney Dental Hospital, warned parents not to be misled by health messages on packaged snacks, saying terms such as "natural" and "fat free" hid negative aspects of the product, such as having lots of sugar and limited nutrients. Loading She said some parents were packing three or four processed or packaged items a day in their child's lunch box. "Ideally processed snack products should be limited to one item and ideally a low-sugar choice, such as popcorn, rice crackers, cheese and wholegrain crackers," she said.

Lunch Box Tips: Include something from each of the five food groups: fruit, vegetables/legumes/beans, dairy, grain (cereal) foods, and lean meats/poultry/fish/eggs.

Limit snacks that are high in sugar and/or saturated fats, for example chips, cakes, chocolate, donuts and biscuits.

Look for grain-based snacks with whole grains and high fibre content.

Pick whole fruit over fruit juice because the vitamins, minerals and fibre make it more filling and nutritious.

Pack water as a drink.

For more information, check out Cancer Council NSW's Healthy Lunch Box interactive web tool.