Similar findings were made after US research into pistachios in 2011. The studies challenge the entire edifice of the Atwater general factor system for measuring calories by asserting that aspects such as food structure affect the amount of calories metabolised by the body. As a result, the absolute calorie content listed on food labels bears little relation to the amount of calories an individual absorbs from the food, experts argue.
Referring to the almond study, Dr Martin Wickham, head of nutrition at Leatherhead Food Research, told FoodNavigator: “A reduction [in calories] of about 20% is groundbreaking and will open the floodgates.” He said the subject was now a matter of intense interest to nutrition scientists. He had himself been asked to give presentations about the topic later this year, he added.
Energy locked up in food structure
Although he said not all the Atwater studies were wrong, he continued: “We have known for many years that the so-called energy content of foods as measured by the Atwater tables is incorrect. A lot of energy is locked up in the food structure.
“It’s time to look back at the Atwater general factor system and see how valid it is. We are well overdue [for this].”
Indeed, some aspects of the Atwater general factor system, which was based on research conducted in the early 1900s, solely depended on studies of Wilbur Atwater’s laboratory assistants. It would not bear the scrutiny of modern scientific method, said Wickham.
Pressure from trade groups representing nut producers would eventually cause the issue to be debated for other foods, he said.
Nuts, seeds, vegetables
“Anything with cell walls acts as a barrier to energy absorption." In particular, the structure of nuts, seeds and vegetables prevented many of the calories from such foods being metabolised, he added.
However, although he recognised the issue could cross the Atlantic and take hold in Europe, it would be some considerable time before the law on calorie labelling could be overhauled. And to his knowledge there were no signs of commercial interest in doing so within the EU.
EU calorie measurement is based on values for fat, protein and carbon, which were firmly set, said Wickham. The only grey area is fibre, for which values vary and are potentially zero, since fibre is considered to be non-digestible.
An overhaul of the Atwater system would take considerable time, but Wickham said it could be done.
The Almond Board of California is petitioning food authorities in the US to reduce the amount of calories allocated to almonds on food labels. This follows a study published in the American Journal of Clinical Nutrition earlier this month, which claims that almonds should be allocated 20% fewer calories than previously thought.
