Nutritionists have encountered a few times what we call the ‘almond mystery’: people who start to eat more almonds don’t get fatter. [Br J Nutr. 2007 Sep;98(3):651-6.] Sounds strange, doesn’t it? Especially if you consider that a handful of almonds is worth at least 150 kilocalories. Researchers at the US Department of Agriculture have solved the puzzle.
We wrote a few days ago about research done by journalists and scientists, which shows that food labels tend to underestimate the number of calories in manufactures food products. A few months ago researchers at the US Department of Agriculture published the results of a study which indicate that the opposite is the case for almonds. You don’t absorb anything like all the calories that almonds contain.
The researchers started by giving 18 test subjects a standard diet for 18 days, followed by a diet that was supplemented by 42 g almonds each day for 18 days, and finally a diet supplemented by 84 g almonds for another 18 days.
So, you don’t absorb anything like all the energy that almonds contain. The second table shows this. It’s also a simplified version. Click on it for the complete version.
The effect is pretty strong: according to the Americans’ calculations you only absorb 68 percent of the energy that the tables suggest is present in almonds.
The researchers gave their subjects whole almonds. Their study says nothing about ground almonds, but the energy uptake from ground almonds is probably considerably higher. The study was funded by the Almond Board of California. [almondboard.com]
“When an 84-g serving of almonds was incorporated into the diet daily, the energy digestibility of the diet as a whole decreased by 5 percent”, the researchers write. “Therefore, for individuals with energy intakes between 2000 and 3000 kcal/day, incorporation of 84 g almonds into the diet daily in exchange for highly digestible foods would result in a reduction of available energy of 100–150 kcal/day.”
The researchers performed a similar study with pistachio nuts. [Br J Nutr. 2012 Jan; 107(1): 120-5.] The results of this study are not as attractive to slimmers who like their nuts. The subjects absorbed 95 percent of the energy contained in the pistachio nuts.
Am J Clin Nutr. 2012 Aug;96(2):296-301. doi: 10.3945/ajcn.112.035782. Epub 2012 Jul 3.
Discrepancy between the Atwater factor predicted and empirically measured energy values of almonds in human diets.
Novotny JA, Gebauer SK, Baer DJ.
USDA, Agricultural Research Service, Beltsville Human Nutrition Research Center, MD, USA. email@example.com
The energy content of foods is primarily determined by the Atwater factors, which may not be accurate for certain food groups. Nuts are a food group for which substantial evidence suggests that the Atwater factors may be poorly predictive.
A study was conducted to determine the energy value of almonds in the human diet and to compare the measured energy value with the value calculated from the Atwater factors.
Eighteen healthy adults consumed a controlled diet or an almond-containing diet for 18 d. Three treatments were administered to subjects in a crossover design, and diets contained 1 of 3 almond doses: 0, 42, or 84 g/d. During the final 9 d of the treatment period, volunteers collected all urine and feces, and samples of diets, feces, and urine were analyzed for macronutrient and energy contents. The metabolizable energy content of the almonds was determined.
The energy content of almonds in the human diet was found to be 4.6 ± 0.8 kcal/g, which is equivalent to 129 kcal/28-g serving. This is significantly less than the energy density of 6.0-6.1 kcal/g as determined by the Atwater factors, which is equivalent to an energy content of 168-170 kcal/serving. The Atwater factors, when applied to almonds, resulted in a 32% overestimation of their measured energy content.
This study provides evidence for the inaccuracies of the Atwater factors for certain applications and provides a rigorous method for determining empirically the energy value of individual foods within the context of a mixed diet. This trial was registered at clinicaltrials.gov as NCT01007188.
PMID: 22760558 [PubMed – indexed for MEDLINE]