Kiwi researchers inform new international dietary guidelines

Media release
17 July 2023

What we eat, and the excess body weight we carry, has now overtaken smoking as the most important preventable cause of disease. Newly updated dietary advice from the World Health Organisation (WHO) on fat and carbohydrate intake is welcomed by New Zealand researchers, as uncertainty remains regarding the ideal composition of healthy diets.

Scientists from the Healthier Lives–He Oranga Hauora National Science Challenge, Professor Sir Jim Mann and Dr Andrew Reynolds, have contributed to research informing the new WHO dietary guidelines, which incorporate the most up-to-date international evidence. 

The WHO recommends that adults limit fat intake to 30% of their total energy intake, with no more than 10% of total energy coming from saturated fats, and less than 1% coming from trans fats.

The recommendation to restrict total fat intake is intended to help prevent excessive weight gain, as fat provides more than twice as much energy per gram than protein or carbohydrate.

“WHO endorsement of advice to reduce total and saturated fat is helpful, as not only are Kiwis eating more fat than recommended (an average of 35% total and 15% saturated fat) but also because some popular diets which include radical restriction of carbohydrate suggest or imply that there is no need for any limitation on fat intake,” says Healthier Lives Director Professor Mann. 

Limiting saturated fat, which is found in meats, dairy and coconut products, is important for reducing the risk of heart disease.  Earlier this year Dr Reynolds published a WHO-commissioned meta-analysis on the health effects of replacing saturated and trans fats with unsaturated fats. 

“Replacing saturated fats with mono and poly unsaturated fats, like those found in vegetable oils, nuts and seeds, and avocados, was associated with lower rates of heart disease,” says Dr Reynolds.

New Zealanders currently get 0.6% of their daily energy intake from trans fats, on average.

“Fortunately, the margarine-type spreads available in New Zealand contain very little trans fat, so we are already meeting the guidelines for trans fat consumption,” says Professor Mann.

And how much carbohydrate should we be eating? The evidence shows that a wide range of carbohydrate intake is compatible with a healthy diet (40-70% of our total energy intake), but it is the quality of the carbohydrate that is of key importance.

The new WHO advice recommends that carbohydrates should come primarily from whole grains, vegetables, whole fruits and pulses.  Pulses include foods such as kidney beans, chickpeas and lentils.

“There are three main groups of dietary carbohydrate: sugars, starch, and fibre. Each of these groups has a different relationship to our health, so just talking about increasing or decreasing carbs is not that useful. Instead we should be talking about reducing sugar intakes and increasing fibre intakes,” says Dr Reynolds.

WHO recommends that adults consume at least 25 grams per day of naturally occurring dietary fibre from their food. But the average intake of dietary fibre in New Zealand is less than 20 grams per day.

“Our research has shown that the potential of dietary fibre to reduce the risk of common diseases such as type 2 diabetes, coronary heart disease and colorectal cancer is much greater than had earlier been appreciated.  For example, an 8 gram per day increase in dietary fibre is associated with a 15% reduction in the risk of developing type 2 diabetes or dying from heart disease,” says Dr Reynolds.

Professor Mann says that having clear and evidence-based dietary advice is important, but further steps are needed to make these recommendations accessible to everyone.

“While it is very helpful to have these updated guidelines, it is essential to have a food environment which enables people to use them – especially those at highest risk of food related diseases.  This is not the case for all New Zealanders.  Many do not have access to, or cannot afford, food choices which would reduce their risk of diet-related diseases,” says Professor Mann.

“We urgently need a National Food Strategy for Aotearoa New Zealand, which has the potential to ensure a secure, sustainable food supply with less detrimental effects on the environment and climate, and which would provide a much greater benefit to human health than is the case at present.”

The World Health Organization (WHO) has updated their guidelines on fat and carbohydrate intake: https://www.who.int/news/item/17-07-2023-who-updates-guidelines-on-fats-and-carbohydrates

Dr Reynolds has also contributed to a new WHO brief on red and processed meats: https://www.who.int/publications/i/item/9789240074828

Professor Jim Mann was interviewed by Dale Husband of Waatea News, talking about what is new in the WHO guidelines and what the Government can do to create a healthier food environment: https://waateanews.com/2023/07/26/professor-jim-mann-director-of-healthier-lives-he-oranga-hauora-national-science-challenge/

For more information, please contact:

Professor Jim Mann
Director, Healthier Lives–He Oranga Hauora National Science Challenge
Co-Director, Edgar Diabetes and Obesity Research Centre
University of Otago

Dr Andrew Reynolds
Senior Research Fellow
University of Otago