Nuts less energy-dense than previously thought

Tree nuts and peanuts may contain less energy than their nutritional labels imply, according to research presented by University of Wollongong (UoW) food scientists.

The UoW research, presented at the Dieticians Australia 2022 conference on 16 August, found the actual kilojoules absorbed from nuts were significantly less than the kilojoules stated on food labels.

The Atwater system has been used globally to calculate kilojoules for more than 100 years and it is the mandated measuring system for Australian food labels. It determines kilojoules based on grams of fat, protein, carbohydrates and alcohol in a particular food, but lead researcher Cassandra Nikodijevic says it doesn’t take into account how our bodies metabolise food.

The research has implications on food labelling that use the Atwater system as its source of nutritional information. The findings suggest the number of kilojoules included on a packet of nuts could be incorrect.

“When it comes to nuts, our bodies can’t absorb all the fat they contain and traditional kilojoule counts do not factor this in,” said Nikodijevic, dietitian and PhD Candidate, School of Medical, Indigenous and Health Sciences, Faculty of Science, Medicine and Health, UoW.

“Due to the crunchy texture of nuts, a portion of the fat remains locked within their fibrous cell walls and cannot be absorbed by our bodies. It is excreted out.

“In comparing the data on the kilojoules from nuts our bodies actually digest, versus standard Atwater measures, we consistently found the kilojoules in nuts and peanuts had been significantly overestimated, in some cases by up to 26%.”

The UoW researchers performed a systemic literature review, looking at multiple papers that analysed the energy content of nuts, and found that there was a substantial decrease in the amount of energy in nuts when these factors were taken into consideration.

For instance, looking at the metabolised energy method, almonds had 26% less kilojoules than measured by the Atwater system, while walnuts and cashews had 22 and 14% less respectively.

Nikodijevic suggested that firmer, brittle nuts will release more energy into the body since people tend to chew them longer and into smaller particles that are absorbed into the body more efficiently.

Nuts for Life, an educational initiative created by the Australian nut industry that provides information about the health benefits of eating nuts, welcomed the finding and suggested that it could result in labelling changes in Australia and lead to consumers eating more nuts.

“Only 2% of Australians eat the recommended 30 g of nuts a day, missing out on the protective heart health benefits of this core food,” said Nuts for Life program manager and dietitian Belinda Neville.

“We’ll continue to support further research on the digestible kilojoules in nuts and explore how changes to labelling could impact consumption. Our aim is to ultimately change food labelling in Australia to better reflect the actual kilojoules absorbed from nuts.”

Image credit: iStock.com/fcafotodigital