Scientists Develop Improved Method to Estimate Calories

BELTSVILLE, Md.U.S. Department of Agriculture (USDA) scientists have developed an improved method for estimating calories in tree nuts and possibly other foods, showing that there are fewer calories in pistachios and almonds than previously thought, according to The Nutrition Society.

The study, conducted by scientists with the Agricultural Research Services (ARS) Beltsville Human Nutrition Research Center (BHNRC) , fed 16 healthy adults pistachios at three different levels: none, 1.5 ounces per day and 3 ounces per day, along with a base nut-free diet. The volunteers ate each pistachio level for 18 days. Researchers collected and analyzed urine and stool samples from all feeding periods. This analysis consisted of measuring calories in the foods that were fed to volunteers (energy in) and measuring the same foods' excreted remains (energy out).

Algebraic equations were used to evaluate data gathered from the biological samples, which enabled the scientists to measure the calories specifically supplied by the target foodthe pistachioseven though the nuts were consumed along with the base diet.

The study suggests that the caloric value of pistachios has likely been overestimated by about 5%, because the fat from the nuts wasn't completely absorbed by the intestinal tract. In theory, the fat within some hard foods is not completely absorbed because it's difficult to digest the food's cell walls, which contain the fat.

Chewing plays a large role in the study, as it begins the digestive process of liberating nutrients from food, which is necessary before nutrients are considered "bioaccessible." As discussed at the 2013 Institute of Food Technologists (IFT) Annual Meeting and Expo,  individuals who chewed almondsa high energy fooda maximum of 40 times, more readily absorbed the smaller particles into the body's system. With fewer chews, the larger particles were eliminated by the body.