Metabolizable energy from cashew nuts is less than that predicted by Atwater factors

Authors: Baer, David; Novotny, Janet

Submitted to: Nutrients
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2018
Publication Date: 12/24/2018
Citation: Baer, D.J., Novotny, J. 2018. Metabolizable energy from cashew nuts is less than that predicted by Atwater factors. Nutrients. 11:33. https://doi.org/10.3390/nu11010033.
DOI: https://doi.org/10.3390/nu11010033

Interpretive Summary: The calories listed on food labels (technically called the metabolizable energy) are typically calculated based on the macronutrient (protein, fat and carbohydrate) content of the food. The macronutrient composition (g/serving) is multiplied by factors related to their energy density (kcal/g). The sum of the energy from each macronutrient is used. The energy density factors (typically called “Atwater factors”) account for digestibility of the macronutrients from the food. Historically, the data used to develop the Atwater factors were from studies conducted over 100 years ago. Recent studies have demonstrated that the energy provided by several tree nuts is less than that predicted by the Atwater factors, though energy available from cashews has never been assessed. The objective of this study was to evaluate the metabolizable energy in cashew nuts. Eighteen healthy adults were enrolled in a randomized, crossover study with two treatment periods. Subjects were fed a fully controlled base diet for 4 wk with either no additions or with the addition of 42 g/d (1.5 servings) of cashew nuts, with the final treatment diets being isocaloric. Complete diet collections were analyzed for nitrogen (for protein), fat, energy, and carbohydrate by difference. During the final week of each intervention phase, subjects collected all feces and urine produced, and these were also analyzed for nitrogen (feces and urine), energy (feces and urine), and fat (feces). The resulting data were used to calculate the metabolizable energy of cashews and the digestibility of macronutrients. The average available energy (calorie) content of a 28 g serving of cashew nuts was 137 kcal (±3.4 kcal SEM) and ranged from 105 to 151 kcal. The mean value of 137 kcal/serving is 16% lower (P<0.0001) than what is typically found on food labels. Digestibility of energy, fat, protein, and carbohydrate was lower for the cashew containing diet compared to the control diet (92.9% vs. 94.9%, p<0.0001 for energy; 96.1% vs. 97.8%, p=0.0009 for fat; 90.1% vs. 91.2%, p=0.0012 for protein; 92.9% vs. 94.9%, p<0.0001 for carbohydrate; for the cashew containing diet vs. the control diet, respectively). In conclusion, cashews provide fewer calories than the values predicted by the Atwater factors, as found on current food labels.

Technical Abstract: Recent studies have demonstrated that the energy provided by several tree nuts is less than that predicted by the Atwater factors, though energy available from cashews has never been assessed. The objective of this study was to evaluate the metabolizable energy in cashew nuts. Eighteen healthy adults were enrolled in a randomized, crossover study with two treatment periods. Subjects were fed a fully controlled base diet for 4 weeks with either no additions or with the addition of 42 g/day (1.5 servings) of cashew nuts, with the final treatment diets being isocaloric. Complete diet collections were analyzed for nitrogen (for protein), fat, energy, and carbohydrate by difference. During the final week of each intervention phase, subjects collected all feces and urine produced, and these were also analyzed for nitrogen (feces and urine), energy (feces and urine), and fat (feces). The resulting data were used to calculate the metabolizable energy of cashews and the digestibility of macronutrients. The average available energy (calorie) content of a 28 g serving of cashew nuts was 137 kcal (±3.4 kcal SEM) and ranged from 105 to 151 kcal. The mean value of 137 kcal/serving is 16% lower (p < 0.0001) than what is typically found on food labels. Digestibility of energy, fat, protein, and carbohydrate was lower for the cashew-containing diet compared to the control diet (92.9% vs. 94.9%, p < 0.0001 for energy; 96.1% vs. 97.8%, p = 0.0009 for fat; 90.1% vs. 91.2%, p = 0.0012 for protein; 92.9% vs. 94.9%, p < 0.0001 for carbohydrate; for the cashew-containing diet vs. the control diet, respectively). In conclusion, cashews provide fewer calories than the values predicted by the Atwater factors, as found on current food labels.