"People nowadays are not spending as much as they should be spending normally for the really healthy, good food."
Monthly bills and one-off financial costs like school uniforms would hit some families harder than others, she said. "They're scrimping already and when something else hits, they still have to feed the kids so they'll just go for the cheapest stuff for their money."
Monthly price figures show soft drinks, coffee and fruit juice prices fell by 2.6 per cent, 5.6 per cent and 6.1 per cent respectively in December.
Ms Stokes warned poor nutrition over extended periods due to costs could lead to long-term health issues for families.
A study led by the University of Otago published this week in the British Medical Journal found the risk of being obese and overweight in children increased as more sugary drinks were consumed.
Lead authors of the study, Dr Lisa Te Morenga and Prof Jim Mann, called for a stronger focus on nutritional information targeting sugar intake.
"It seems easier to overeat if your diet includes lots of sugary foods and drinks. When you overeat you gain weight," Dr Te Morenga said.
Heart Foundation national nutrition advisor Delvina Gorton said: "Ideally we'd like to see the prices of fruit and veges going down to encourage people to eat more and the price of sugary drinks, which we want people to have less of, going up."
Ms Gorton advised people to look for seasonal specials on fruit and vegetables. For example, a carrot costs about 30 cents at the moment, she said.
Statistics NZ price manager Chris Pike said the monthly decline in non-alcoholic beverage prices reflected lower overall food prices for the month.
Prices were down 0.2 per cent in December and 1 per cent on a year earlier.