Is a lunchbox bad for your child's health? The latest research from the food standards agency suggests it might be. Of 556 primary schoolchildren's lunchboxes surveyed, nine out of 10 had too much saturated fat, salt and sugar, and only 21% met the health standards laid down for school meals providers.

But lunchboxes, as every parent knows, are often the preferred option for children themselves, and the truth is that a packed meal can be a nutritious and tasty option.

Getting the balance right is the key message with healthy packed lunches. There are no good or bad foods - but there are good and bad diets. What this means is that food that is high in saturated fat or sugar should not be banned completely. If you try to cut sweets, chocolate or cakes out of your child's diet you may well create a craving for the food you are trying to get them to do without. The problem is about portion sizes and frequency - once in a while will not do you any harm at all, but if it is a large amount every day you - and your child - could be heading for problems.

What this means for the packed lunch is do not leave out the treats altogether, but try to choose the healthier options - a currant bun rather than a chocolate cake, wholemeal or wholegrain bread rather than white bread, water or milk rather than a fizzy drink. Increase the amount of fresh fruit, salad and vegetables you are putting in - fewer than half the lunches surveyed had any of these at all - and try to make it more fun by adding low-fat dips.

Variety is key: another finding of the research was that 87% of packed lunches contained white bread sandwiches, followed by crisps (71%), a biscuit or chocolate bar (60%), and a yoghurt or fromage frais (48%). Of course, it is easy to get into the habit of making the same meal for your child each day - especially if you know it is what he or she likes - but variety is important and it is not true that healthy has to mean lots of work or a gourmet-style meal. It is just as quick and easy to open a tin of tuna or wash a few cherry tomatoes as to make a sandwich - and if you think ahead and, for example, leave aside some cooked pasta from a meal the night before to mix with vegetables, you can actually reduce your workload.

Don't be too ambitious, though. If your child refuses to drink milk but prefers flavoured milk, opt for the flavoured. Even if adding flavouring means more sugar, he will not be missing out on the valuable nutrients in milk. If he will have a currant bun but not a wholemeal currant bun, go for the ordinary one. What you are aiming for here is a generally healthy attitude to food and an openness to a variety of different things - if you achieve that, you will be doing all you can to set your child up for a healthy future.

What you should not do, though, is take lunchboxes on their own, out of context from the rest of a child's diet: there is no point in sending your child off to school this week with a plastic box full of carrots, pitta bread and houmous if breakfast was non-existent and if supper is going to be a sausage roll and chips.

What we need is a bit of joined-up thinking on children's eating: the message for parents is that example is a lot more important than talk or, for that matter, what you put into a lunchbox. If your child sees you eating healthy food, she or he will be more likely to eat healthily too - and not just now, but in the future.

Sample lunchbox

Apple

Government recommendations are that we all eat at least five portions of fruit and vegetables a day. Studies show that people who eat a diet high in fruit and vegetables have a much lower risk of cardiovascular disease and some types of cancer, so getting your child into good fruit-eating habits now really is important.

Carrot

Providing a variety of fresh fruit and vegetables is good, as each is rich in different vitamins. Carrots are a rich source of vitamin A, which is good for eyesight and is an antioxidant, which helps prevent cancer-causing free radicals.

Flavoure milk

Children need large amounts of calcium because they do not achieve peak bone mass until they stop growing. Milk is an important source, so if your child flatly refuses to drink plain milk, it is worth providing flavoured - certainly a lot better than a fizzy drink. By primary school, children should be drinking semi-skimmed milk as it has slightly more calcium but, more importantly, less fat. By this stage you need to be educating them into a healthy adult-style diet.

Tuna and sweetcorn sandwich

Tuna tinned in brine has a slightly lower fat content, but should be rinsed to reduce the salt content. Government recommendations are that we eat a portion of oily fish and a portion of white fish each week. Tuna is a white fish, which is a good source of the protein children need for growth and repair, and is high in vitamins and minerals. Sweetcorn tends to be very popular with children, and as it is a carbohydrate, it is a valuable source of energy. The wholemeal bread provides fibre, which helps reduce the risk of constipation - sometimes a problem in primary schoolchildren.

Wholemeal hot cross bun

Every child likes a treat in a lunchbox, preferably something sweet - but it does not have to be a heavily-processed chocolate cake laden with fat and calories. A currant bun will probably have less sugar - the currants add sweetness and provide vitamins and minerals at the same time.

· Dr Toni Steer is a nutritionist at the Medical Research Council's human nutrition research unit

· Research by Joanna Moorhead