First pig farming exposes put people off buying pork, now ham and bacon in school lunches is a no-no.

Cancer researchers have warned that parents should not give their children ham sandwiches as processed meat - including salami, ham, bacon and pastrami - can increase the risk of bowel cancer in later life.

The lunch that Meadowbank School pupil Ben Manning enjoyed this week - a peanut butter sandwich, an apple, rice crackers and a muesli bar - would keep most nutritionists happy but they acknowledge that some parents might have an uphill battle to encourage their children to eat healthy lunches.

By comparison, Ben, aged 8, is easily pleased. His favourite fruits are "apples, oranges, kiwifruit, basically everything" and his favourite vegetable is the carrot.

Keeping the contents of school lunch boxes interesting enough for kids to eat the food inside is hard enough for parents, but bad press on one of the main ingredients could make things worse.

The World Cancer Research Fund International (WCRFI), has warned about the dangers of giving children processed meat but local experts have recommended taking the research with a grain of salt.

Dr Jan Pearson, Health Promotion Manager for the Cancer Society, said the WCRFI study had come out of the United Kingdom where access to healthy fresh foods may be more restricted than in New Zealand.

"It falls back on the poor parents to try and provide a range of food."

However, Pearson said parents can use a variety of foods to replace processed meats that are healthier options.

For example, sandwiches with cheese or humus are good healthy options, and even Marmite instead of meat.

Nutritionist Nikki Hart agreed that moderation and variety is the key to a healthy child and a healthy adult later in life.

"I think there is a lot of scaremongering out there, she said. "I think you should just stick to basics, there's nothing wrong with a jam sandwich."

Hart said the trick is not to hide junk food from children, but to monitor it and allow it in moderation."The kids know the food is out there but it's how you control it."

For example, while some parents might baulk at the idea of a Marmite and chip sandwich in their child's lunchbox, Hart said, it was a way of satisfying the child's craving while stopping them having an entire bag of salty chips instead.

Both Pearson and Hart favoured flavoured yoghurts as part of the lunchbox mix.

It was a good way to get protein and calcium into a young body, especially when little children often didn't like the texture of fruit yoghurt, they said.

Auckland University nutrition expert Dr Clare Wall agreed that evidence was always changing depending on how research was carried out.

"We have to be careful about the way we interpret studies in nutrition."

In her opinion there was nothing wrong with a ham sandwich two or three times a week providing the rest of the week's lunches did not contain meat.

Parents needed to be realistic and practical when planning a child's lunch, Wall said. She recommended keeping lunch interesting by using a range of healthy breads such as pita pockets and mini rolls instead of the usual sliced bread.

Vegetarian fillings such as grated carrots and cucumber were a good alternative to meat, she said.

Home baking, especially savoury muffins, were an ideal substitute for biscuits. Other healthy option snacks can include dried fruit and nuts.

Primary school principals told the Herald on Sunday they had shied away from giving parents advice on nutrition.

David Ellery, principal of Somerville Intermediate in Howick, said he once warned parents not to let their children bring jelly crystals to school after a craze started to take hold among the pupils.

But he believed most of the children had good diets, he said.