New Zealand could slash emissions and save billions of healthcare dollars over coming decades if more Kiwis moved to a plant-based diet, a new study suggests.

Lead researcher and Otago University medical student Jono Drew said international studies had highlighted the climate and health co-benefits that came from consuming diets rich in plant foods like vegetables, fruits, whole grains and legumes.

"We wanted to understand if this holds true here in New Zealand, and to tease out which eating patterns could offer the greatest co-benefits in this context."

His team built a database that estimated greenhouse gas emissions from foods commonly eaten by Kiwis, and considered specific parts of the life cycle of each food, such as farming and processing, transportation, packaging, distribution, refrigeration needs, and supermarket overheads.

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Next, they modelled the climate, health, and health system cost impacts stemming from a range of dietary scenarios.

Senior author Dr Alex Macmillan said results from the study showed emissions varied considerably between different foods in New Zealand.

As a general rule, the climate impact of animal-based foods, particularly red and processed meats, tended to be substantially higher than that of whole plant-based foods, including vegetables, fruits, legumes, and whole grains.

"Fortunately, foods that are health-promoting tend also to be those that are climate friendly," she said.

"Conversely, certain foods that carry known health risks are particularly climate-polluting. Red and processed meat intake, for instance, is associated with an increased risk of cardiovascular disease, type-2 diabetes and certain cancers."

The study ultimately showed a population-level dietary shift could potentially offer diet-related emissions savings of between 4 to 42 per cent annually.

Added to that was health gains of between 1-1.5 million quality-adjusted "life-years" – or those equivalent to a year of optimal health – and cost savings to the health system of $14 to $20 billion over the lifetime of the current New Zealand population.

Drew said the analysis reveals emissions savings equivalent to a 59 per cent reduction in New Zealand's annual light passenger vehicle emissions could be possible if New Zealand adults consumed an exclusively plant-based diet and avoided wasting food unnecessarily.

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"We thought it was important to show what was possible if people were willing to make changes to their eating pattern, and what would be possible if our entire population made a significant shift in that same direction."

The researchers argued the findings should prompt national policy action, including revising the New Zealand dietary guidelines to include messaging on climate-friendly food choices.

They also advocated for the implementation of other policy tools, such as pricing strategies, labelling schemes, and food procurement guidelines for public institutions.

Beef+Lamb NZ's chief insight officer Jeremy Baker was however critical of some findings in the study, which he described as "overly simplistic".

Baker questioned how the study had considered the impact of methane, and didn't take into account that the red meat sector had reduced its emissions by 30 per cent since 1990.

"We are one of the few sectors of the economy that have reduced our emissions, so I think that's a little unfair."

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Baker said the paper also didn't note that just a small proportion of land currently used for sheep and beef operations was suitable to use for production of plant-based foods.

"They also don't point out that red meat consumption in New Zealand has been dropping for quite a long time."

Consumption of red meat among Kiwis has fallen by 42 per cent over the past decade, while mutton, once a staple of Kiwi dinner tables, has plunged by nearly three quarters over that time.

The group has already responded to successive studies that have linked high red meat consumption with greater death rates and some diseases.