Preparing a lunch box is a challenge. Not only do most schools insist on a healthy lunch pack, but it must also stay fresh for at least three hours and your child must find it appetising. Dieticians agree that a balanced school lunch should consist of at least one portion of starch, one portion of protein and one fruit or vegetable portion.

"The brain makes up 2% of our body weight, but uses between 20% and 50% of the energy that the body gets from food," says Linda McCourt, advisory dietician on Savvy Kids Food by Sarah and Rupert Mc Kerron of McNab's Wellth.

She says the brain needs 23 minerals and vitamins to stay sharp. If a deficiency arises, the frontal lobe (which controls concentration and reasoning) is the first part of the brain to suffer. When that happens, the part of the brain that controls the emotions becomes more dominant. According to Linda, this can cause children to become more aggressive, impulsive, selfish and moody.

Golden rules for healthy meals
RULE 1 Buy a lunch box with divisions
"Nobody likes nuts that smell of cheese, or carrot sticks covered in peanut butter. You can also easily pack leftover salad, stir-fry or chicken in a lunch box with divisions," says Pretoria dietician Alta Liebenberg.

RULE 2 Provide variety
If you pack the same lunch day after day for an entire week, it will eventually return home untouched. Children want variety. When doing the monthly shopping, buy three packs of different types of bread (rolls, bagels, ciabatta, pita bread or muffins) and freeze them. Take out something different each day.

RULE 3 Keep it fresh
To keep food fresh, choose a lunch box made of good-quality plastic that seals properly. Wrap your child's sandwiches in wax paper or foil. Foil is good for moist fillings. Rather avoid cling film, especially in summer, because the food could absorb some of the chemicals in the plastic if it goes soft or melts.

RULE 4 Keep it cool
If you pack a lunch that could melt, find out if there's a cool place or fridge where your child can leave the lunch box. If not, you could invest in a small cooler bag such as those used for wine or beer. It will come in especially handy if your child has sports practice after school. Freeze the bag overnight, take it out early in the morning, and pack the lunch into it.

RULE 5 Use leftovers
Leftover food is safe, as long as it is stored in the fridge and used within two days or so. Leave the lunch box in the fridge overnight, but do bear in mind that food such as fish, chicken or hardboiled eggs can have a strong smell when removed after a bit of time in a lunch box.

RULE 6 Freeze it
If you are a working mom, make fillings using leftover chicken, fish or mince over weekends (by adding chutney, mayonnaise or salad dressing) and freeze them. Most protein fillings can be frozen safely for approximately three weeks. Avoid fillings with a high water content such as tomatoes, cucumber and lettuce, as they will make the sandwiches soggy. Freeze your child's juice – cold juice is much more refreshing.

Lunch that packs a punch
Some smart high-energy options include the following:
Fruit
Cut fruit into pieces rather than packing a whole apple or banana. Fruit that is firm enough to survive three hours in a lunch box includes apples, bananas, strawberries, grapes, citrus fruit and pineapple. Dried fruit and nuts are also an excellent lunch-box choice – especially if your child does sport after school.

Vegetables
Celery, cherry tomatoes, cucumber and carrots. Seeds Sunflower and pumpkin seeds are delicious fresh or roasted and can also be added to raisins or other dried fruit. Protein Biltong, hard cheese that doesn't go soft easily, hardboiled eggs, ham, chicken pieces and peanut butter.

Treats
Muesli or seed bars, health rusks, bran muffins, date truffles and yoghurt.

What is junk food?
Junk food is classified as food containing unnatural colourants and flavourings, made of highly refined white flour or sugar, high in sodium or containing more than 1g per 100 g of saturated fats.

Did you know?
A can of carbonated soft drink contains an average of 10 teaspoons of sugar, while many of the so-called fruit juice cordials contain loads of sugar and colourants and virtually no fruit.