Almond Form and Processing Impacts Metabolizable Energy Value in Humans

Abstract

We have previously demonstrated that the metabolizable energy (ME) of whole roasted almonds is less than that predicted by the Atwater factors, and thus lower than the value currently listed on the Nutrition Facts panel. Studies have shown that incomplete disruption of the cell wall during mastication of whole almonds leads to decreased lipid absorption, suggesting that the food matrix plays a role in determining the ME value of a food. However, data are lacking on how food structure and processing (roasting, slicing or grinding) impact the ME value of almonds. The objective of this research was to determine the ME value of different forms of almonds.We conducted a randomized, crossover design study in healthy individuals (n = 18) to measure the ME of the following forms of almonds, within the context of a completely controlled diet (18 days each): whole, natural almonds (42 g/day); whole, roasted almonds (42 g/day); diced almonds (42 g/day); almond butter (42 g/day); and control (0 g/day). After 9 days of adaptation to each diet, participants collected all urine and fecal samples for approximately 9 days. The gross energies of the diets, almonds, urine, and feces were measured by adiabatic bomb calorimetry. The ME value of the nuts was determined using the paired‐diet approach.Based on the measured chemical composition of the almonds fed, the estimated ME (kcal/g) by use of Atwater specific factors for whole natural almonds, whole roasted almonds, diced almonds, and almond butter was 5.91, 6.01, 6.04, and 6.18, respectively. The empirically measured ME value (kcal/g) for whole natural almonds, whole roasted almonds, and diced almonds was 4.42, 4.86, and 5.04, significantly lower than predicted (P < 0.001 for all); while the ME for almond butter was similar to predicted (6.53 kcal/g; P = 0.08). Available calories from almonds is dependent on the form in which they are consumed. Furthermore, the measured ME of whole natural almonds, whole roasted almonds, and diced almonds is significantly lower than that estimated by the Atwater factors (30.4%, 24.5%, and 22.1%, respectively).Atwater factors (general or specific) provide inaccurate estimates of ME for almonds whether they are consumed whole, whole roasted, or chopped, whereas they are accurate for butter. It is likely that estimates of macronutrient digestibility used to develop the Atwater factors are incorrect for nuts.Support or Funding InformationUSDA and Almond Board of California