Scientists Improve Calorie
U.S. Department of
Agriculture (USDA) scientists have improved the method for estimating calories
in tree nuts, showing that there are fewer calories in pistachios and
almonds than previously thought. The modified method should also work well for other
foods, according to the scientists with the Agricultural Research Service
(ARS), USDA's in-house research arm.
Chewing begins the digestive
process of liberating nutrients from food. This process is necessary before
nutrients are considered "bioaccessible." 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.
Physiologists David Baer and
Janet Novotny at the ARS Beltsville Human Nutrition Research Center in
Beltsville, Md., fed 16 healthy adults pistachios at three different levels:
none, 1.5 ounces per day, and three ounces per day, along with a background or
"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).
Novotny, also a
mathematician, wrote a series of algebraic equations to evaluate data from the
biological samples and to isolate and measure the calories specifically
supplied by the pistachios separately from the base diet consumed. “The base
diet always consisted of the same foods and composition, thus allowing us to
tease out the caloric value of the single target food,” says Novotny.
The study suggests that the
caloric value of pistachios has likely been overestimated by about 5 percent,
because the fat from the nuts wasn't completely absorbed by the intestinal
tract. The study, published in the British Journal of Nutrition in 2011, was
supported by USDA and Paramount Farms, Inc., Los Angeles, with an improved
method and reported in the September 2013 issue of Agricultural Research
and Novotny conducted a similar human clinical trial in which they fed the
volunteers three different levels of whole almonds as part of a carefully
controlled diet for an 18-day period. According to food labels, almonds provide
168 calories per 1-ounce serving, but the researchers found that the same
serving actually provided 129 calories when computed by the modified method.
This difference was due in large part to loss of undigested fat, protein, and
carbohydrate in the stools, according to the authors.
study showed that it is possible that the total number of available calories
from certain whole nuts, and perhaps other similar foods, may be lower than
originally estimated. The study, published in the American Journal of Clinical Nutrition in 2012, was supported by
USDA and Almond Board
Labels: Agricultural Research, Almond Board of California, ARS, David Baer, Janet Novotny, NUTS HAVE FEWER CALORIES THAN EXPECTED, Paramount Farms, pistachio, Scientists Improve Calorie Estimation Method, USDA