At first glance, the study results beg the question, how can a food’s calorie count suddenly change when the composition of the food itself hasn’t?
The answer is that David Baer, PhD, and his team from the USDA’s Agricultural Research Service (ARS) used a new method of measuring the calories in almonds, which built on traditional methods and allowed the researchers to determine the number of calories from almonds that are actually absorbed during digestion.
Resulting data showed a 28-gram serving of almonds (about 23 almonds) has 129 calories versus the 160 calories currently listed on food package labels.
These significant results not only may lead people to choose almonds more often as a smart snack — they may have implications for certain other foods as well.
In fact, the same research team also recently conducted a similar study using pistachios, finding a 5 per cent decrease in pistachios’ calorie count compared to the 20 per cent decrease in almonds’.2
In the study’s discussion section, the authors considered the potential implications of substituting other foods with almonds in a calorie-controlled study. Based on the data, “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 per cent. Therefore, for individuals with energy intakes between 2,000 and 3,000 kcal/d, incorporation of 84 g almonds into the diet daily in exchange for [the same number of calories from] highly digestible foods would result in a reduction of available energy of 100-150 kcal/d. With a weight-reduction diet, this deficit could result in more than a pound of weight loss per month.”1
The new study’s results support previous research indicating that the fat in almonds is not completely absorbed during digestion, due to almonds’ natural cellular structure, which encapsulates the fat, thereby impeding its absorption.3 This implies that traditional methods of calculating calories overstate those calories coming from almonds because they do not account for the incomplete digestibility and absorption of fat and the other macronutrients.
Traditionally, foods’ calorie counts are calculated based on a system developed by Atwater et. al.4 more than 100 years ago. Known as the Atwater general factors, the system assigns calorie values for every gram of protein, fat and carbohydrate found in a given food (4 kcal/g for protein, 9 kcal/g for fat and 4 kcal/g for carbohydrate).
However, as the new study notes, “There have been few, if any, studies that looked at the calorie value of a whole food when consumed as part of a mixed diet that could confirm the accuracy of Atwater’s coefficients.”
So, for this study, the researchers expanded on Atwater’s approach, using a specially designed diet and new method of calculation that allowed them to understand the calories provided by almonds when eaten as part of a mixed diet.
According to Karen Lapsley, DSc, Chief Science Officer of the Almond Board of California, “This new information indicates we get fewer calories than we thought from a handful of almonds. Considering the 100-plus year history of traditional methods of nutritional analysis, this is really starting to get interesting.”
The results reported in the study are applicable only to whole almonds, and while no additional studies have been conducted yet, the discrepancy in calories may not be consistent for other forms of almonds such as almond butter or slivered or sliced almonds as the finer particles may lead to more complete digestion. Globally, however, whole almonds are consumed in far greater proportion than are other forms.
The California almond industry is now working with government agencies to determine what these study results may mean for future consumer education about almonds, such as nutrition labeling.
Almonds are low in saturated and trans fats. A healthy diet low in saturated and trans fats may reduce the risk of heart disease. Almonds also are nutrient-rich. Per 30 gram serving, almonds contain more protein (6.4 g), dietary fibre (3.7 g), calcium (79.2 g), vitamin E (7.9 mg), riboflavin (0.3 mg), and niacin (1.0 mg) than any other tree nut.
eStudy at a Glance:
Study: A study was conducted to compare, for almonds, the measured energy value and the energy value calculated using Atwater factors, the primary method used to determine the energy content of foods. Eighteen healthy adults consumed, in random order, one of three isocaloric diets for 18 days each. The three diets were administered to subjects in a crossover design and the diets contained 1 of 3 almond doses: 0, 42, or 84 grams per day. During the final 9 days of each treatment, volunteers collected all urine and faeces, and samples of the diets, urine, and faeces were analysed for macronutrient and energy contents. From these values, the “measured” (metabolisable) energy content of the almonds was determined.
Results: The measured energy content of almonds, when administered as part of a mixed diet, was 129 kilocalories per 28-gram serving (4.6 +/- 0.8 kcal/g). This is significantly less than the energy content of 168-170 kcal per serving (6.0 – 6.1 kcal/g), calculated using the Atwater factors. When applied to almonds, the Atwater factors resulted in a calculated energy value that was 32 per cent greater than the measured energy value.
Conclusion: This study provides evidence that almonds provide approximately 20 per cent fewer metabolisable calories than originally thought. The Atwater factors, when applied to certain foods such as almonds, may result in an overestimation of their energy content because of the inability to account for the incomplete digestibility and absorption of macronutrients such as fat.