Study Provides New Way To Measure Calories Using Whole Almonds

Resulting data showed a one-ounce serving of almonds (about 23 almonds) has 129 calories versus the 160 calories currently listed on the Nutrition Facts Panel. The results may have implications for certain other foods as well.

13 Jul 2012 --- A study conducted by scientists from the United States Department of Agriculture (USDA) and released in the August issue of the American Journal of Clinical Nutrition (AJCN) provides a new understanding of almonds’ calorie count, showing that whole almonds provide about 20 percent fewer calories than originally thought.

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 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 actually digested and absorbed from almonds. Resulting data showed a one-ounce serving of almonds (about 23 almonds) has 129 calories versus the 160 calories currently listed on the Nutrition Facts Panel. The results may have implications for certain other foods as well.

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%. Therefore, for individuals with energy intakes between 2000 and 3000 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.”i

The new study’s results support previous research indicating that the fat in almonds is not absorbed as easily as the fat in most other foods, due to almonds’ natural cellular structure.ii This implies that traditional methods of calculating calories overstate those calories coming from almonds because they do not account for the fact that fat digestibility from nuts is less than that from other foods.

In fact, the same research team also recently conducted a similar study using pistachios, finding a 5 percent decrease in pistachios’ calorie count compared to the 20 percent decrease in almonds’.

Most often, foods’ calorie counts are calculated based on a system developed by Atwater et. al.iv 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 whole food within a mixed diet that could confirm…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 extrapolate the calories from almonds eaten as part of a full diet.

According to Karen Lapsley, DSc, Chief Science Officer for 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 study notes that its results 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 Facts panels.

Almonds are nutrient-rich. Ounce for ounce, they contain more protein (6 g), dietary fiber (3.5 g), calcium (75 g), vitamin E (7.4 mg), riboflavin (0.3 mg), and niacin (1 mg) than any other tree nut. Almonds are also heart smart. Scientific evidence suggests, but does not prove, that eating 1.5 ounces per day of most nuts, such as almonds, as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease. A one-ounce handful contains 13 grams of unsaturated fat, only 1 gram of saturated fat and no cholesterol.

The Study: 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 Atwater factors, the primary method used to determine the energy content of foods. To calculate the measured energy value of almonds, eighteen healthy adults consumed one of three diets for 18 days each. The three treatments were administered to subjects in a crossover design where 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 feces, and samples of diets, urine, and feces were analyzed for macronutrient and energy contents. From this, the “measured” (metabolizable) energy content of the almonds was determined.

Results: The energy content of almonds in the human diet was measured at 129 kilocalories per 28-gram (or one-ounce) serving (4.6 +/- 0.8 kcal/g). This is significantly less than the calculated energy content of 168–170 kcal per serving (6.0 – 6.1 kcal/g) for the almonds used in this study as determined by the Atwater factors. When applied to almonds, the Atwater factors resulted in a calculated value that was 20 percent greater than the measured energy value.

Conclusion: This study provides evidence that almonds provide approximately 20 percent fewer metabolizable calories than originally thought. The Atwater factors, when applied to certain foods, may result in overestimation of their measured metabolizable energy content. Traditional methods overstated the calories from almonds because they do not account for the fat that is not fully absorbed. This is thought to be due, in part, to the fiber content and/or the rigidity of almond cell walls.

Novotny JA, Gebauer SK, Baer DJ. Discrepancy between the Atwater factor predicted and empirically measured energy values of almonds in human diets. American Journal of Clinical Nutrition. 2012 ajcn.035782; First published online July 3, 2012.doi:10.3945/ajcn.112.035782

Ellis PR, et. al. Role of cell walls in the bioaccessibility of lipids in almond seeds. Am J Clin Nutr 2004; 80:604-13.

Baer DJ, Gebauer SK, Novotny JA. Measured energy value of pistachios in the human diet.British Journal of Nutrition 14 January 2012 107 : pp 120-125

Atwater, WO, Bryant AP. The availability and fuel value of food materials. Storrs, CT: USDA, 1900 (Agriculture Experiment Station 12th Annual Report 73-110.)