A food for toddlers marketed as being made almost entirely from fruit and vegetables contains so much sugar it should be deemed confectionery by experts, the Federal Court has heard.

Legal action against food giant Heinz has started in Adelaide, with the consumer watchdog alleging the "Little Kids Shredz" range misleads the public about the nutritional content of the product.

The Australian Competition and Consumer Commission (ACCC) launched the legal action in June last year, after a complaint by the Obesity Policy Coalition about food products for toddlers.

The packaging of the Shredz products features images of fruit and vegetables and states it is "99 per cent fruit and veg".

But in his opening address, counsel representing the ACCC, Tom Duggan, told the court the "berries, apple and veg" variety contains 68.7 grams of sugar per 100 grams.

"This product has added sugar, as a consequence it is not a nutritious alternative to the fruit and vegetables depicted on the packaging," he said.

Mr Duggan said the court would hear evidence about the use of apple juice concentrate in the product which is an added sugar.

"There are two important differences between the Shredz product and dried fruit, one is the addition of the apple juice concentrate," he said.

"Accepting that it is a naturally occurring sugar, it is still an added sugar."

The court heard the sugar content of the product defies Heinz's own health guidelines.

"Heinz's internal guide specifies that the less than 30 per cent [sugar] guide includes the use of fruit juice and fruit paste," Mr Duggan said.

"This is an extra food, it is not a substitute for fruit and veg."

Rosemary Stanton, who helped devise Australia's dietary guidelines, was called on to give evidence. ( ABC News: Rebecca Opie )

Nutritionist and dietician Rosemary Stanton gave evidence to the court.

Dr Stanton, who helped devise the Australian dietary guidelines, said the bars more closely resembled confectionery than fruit or vegetables.

"Confectionery with added vitamins is still confectionery," she said.

Under cross-examination, Dr Stanton agreed with counsel representing Heinz, Rowena Orr, that the bars had some dietary fibre and nutrients.

But she told the court the same could be said of other junk foods.

"There are positive nutrients in these products ... just as there are positive nutrients in a Big Mac," she said.

Dr Stanton told the hearing there were many foods which had been given a "halo of respectability" just by having some nutrients added to them.

"We have 50 per cent of children, in the one-to-three or the two-to-three age group, who are having more than the maximum amount of recommended sugars. We have some very real problems," she said.

"What we have tried to do with the guidelines is to have them as food-based guidelines, not nutrient-based guidelines."

Heinz rejects ACCC claims, says food 'appropriate'

In a statement, Heinz said it strongly rejected claims made against it by the ACCC about the packaging.

"The Shredz products were snack foods available in small individually packaged serves appropriate for children aged one to three," it said.

"The Shredz products had a similar nutrition profile to dried apple or sultanas.

"Heinz stands behind the Shredz products and their packaging."

The ACCC has previously said it was seeking pecuniary penalties, corrective notices and costs.

The hearing is expected to last five days.