Improved technique for measuring fecal energy loss in normal and malabsorbing humans

Fecal energy concentration is measured by bomb calorimetry on freeze-dried stool samples. Some of the energy-containing fecal compounds are volatile in the pH ranges of normal stool and hence may be lost during sample preparation. We found that significant amounts of volatile fatty acids and lactic acid are lost during lyophilization. Fecal alkalization caused an increase of 9.8% of measurable energy in stools from normal individuals and 25% in stools from patients with untreated exocrine pancreatic insufficiency. We conclude that previous reports of fecal energy concentration that did not use an alkalization procedure are probably underestimations. We recommend fecal alkalization before lyophilization in future measurements of fecal energy excretion.