Canterbury University clinical psychologist professor Julia Rucklidge, who co-authored an editorial in The New Zealand Medical Journal, with Otago University psychiatry professor Roger Mulder, said all the messaging to pregnant women was about what not to eat, rather than what they should be eating.
"But then it means that they end up making food choices that are often going to be often ultra-processed, which at the end of the day we now know - from research that's been coming out over the last couple of decades - that eating those types of foods has been identified as leading to increased mental health problems in children."
The article quotes The Growing Up in New Zealand study, which found only 3 percent of pregnant women fully adhered to the Manatū Hauora Ministry of Health's food and nutrition guidelines in pregnancy, with just one in four eating the recommended amount of fruit and vegetables.
"Maternal low adherence to a 'healthy dietary pattern' in the third trimester is significantly associated with children's depression and anxiety symptom trajectories."
Other research showed ultra-processed foods made up 45 percent, 42 percent, and 51 percent of energy intake in babies and toddlers at 12, 24 and 60 months respectively.
Health Ministry data from 2022 found just 4.3 percent of boys and 7.2 percent of girls aged two to 14 years were eating the recommended amount of fruit and vegetables.
"At the same time, we see a doubling of children being diagnosed with psychiatric problems over a decade.
"From 2012 to 2022, the number of children two to 14 years diagnosed with an emotional or behavioural problem rose from 4.4 percent to 8.6 percent in boys and 2.1 percent to 3.8 percent in girls.
"These percentages represent an increase from 26,000 children in 2012 to 53,000 children in 2022."
Rucklidge, who has done extensive research on the influence of nutrition on mental health, said education could help change attitudes but money was "the heavy hitter".
"As the long history of cigarettes has shown, people really only start to change their behaviour when it costs them."
She lamented the lack of political appetite for a fat or sugar tax.
"I know it's not on anyone's agenda this week.
"It's great people are talking about doubling the number of training of places for clinical psychologists, I'm a clinical psychologist, we do need more of them.
"But let's get rid of the root causes of poor mental health, let's stop people getting unwell, stressed and anxious, rather than just putting more ambulances at the bottom of the cliff."
The paper also recommends mandatory reporting of ultra-processed foods in supermarkets as a proportion of sales, stopping direct marketing of junk food to children, warning labels on packaging, and limiting the number of fast food outlets in some neighbourhoods.
