The measured energy value of pistachio nuts in the human diet

Authors: Baer, David; Gebauer, Sarah; Novotny, Janet

Submitted to: British Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2011
Publication Date: 4/20/2011
Citation: Baer, D.J., Gebauer, S.K., Novotny Dura, J. 2011. The measured energy value of pistachio nuts in the human diet. British Journal of Nutrition. 28:1-6.

Interpretive Summary: Previous studies have suggested that fat from nuts is more poorly absorbed than fat from other food sources. If fat from nuts is poorly absorbed, then the utilizable calories contained in the nuts would be less than the value used for food labels. A pistachio feeding study was conducted in which 16 volunteers consumed three diets for 18 days each as part of a controlled diet. Pistachio content of the diets were 0 servings per day, 1.5 servings (42 g or about 1.5 oz) per day, and 3 servings (85 g or about 3 oz) per day. Urine and fecal samples were analyzed for calorie content. Blood was also collected after each treatment period and analyzed for cholesterol. The usable calories contained in pistachio nuts was calculated from differences in calorie excretion during the different dietary treatments. The measured calorie density of pistachios was found to be 3% less than the currently accepted value used on nutrient labels. The pistachio nut intervention lowered LDL cholesterol by 6%, but did not significantly change total cholesterol, HDL cholesterol, or plasma lipids. In conclusion, pistachio nuts contain less usable energy than the value on food labels. Accurate information about calorie content of foods is important for reliable food labeling. This information will be used by scientists and health care professionals.

Technical Abstract: Previous studies have suggested that lipid from nuts is more poorly absorbed than that from other food sources. If lipid from nuts is poorly absorbed, then the metabolizable energy contained in the nuts is less than that predicted by the Atwater general factor for fat of 37 kJ(9 kcal)/g. A crossover feeding study was conducted in which 16 volunteers consumed pistachios at three levels for 18 days each as part of a controlled diet. Pistachio amounts were 0 oz/d, 1.5 oz/d, and 3 oz/d. Urine and fecal samples were collected, and urine, feces, and diet were analyzed for nitrogen, fat, total dietary fiber, ash, and combustible energy. Blood was also collected after each treatment period and analyzed for plasma lipids. Energy value of pistachio nuts was calculated from differences in energy excretion during the different dietary treatments. The measured energy density of pistachios was found to be 22.9 kJ/g (5.49 kcal/g), which is less than the currently accepted energy value for pistachios of 23.7 kJ/g (5.67 kcal/g), as calculated using the Atwater general factors. The pistachio nut intervention lowered LDL cholesterol by 6%, but did not significantly change total cholesterol, HDL cholesterol, or plasma lipids. In conclusion, pistachio nuts contain less metabolizable energy than that calculated from the Atwater general factors. Accurate information about metabolizable energy content of foods is important for reliable food labeling.