Gas production in humans ingesting a soybean flour derived from beans naturally low in oligosaccharides

Background: Ingestion of soy products may cause excessive intestinal gas. T his gas results from colonic bacterial fermentation of the indigestible oli gosaccharides raffinose and stachyose, which are present in high concentrat ions in legumes. Objective: The objective of the study was to compare gas production and gas eous symptoms in healthy volunteers after ingestion of 34 and 80 g soy flou r made from either conventional soybeans or soybeans naturally low in indig estible oligosaccharides. Design: In a double-blind, randomized, crossover protocol, breath hydrogen (an indicator of carbohydrate malabsorption), flatus frequency, and abdomin al symptoms were assessed after subjects ingested the soy products and afte r 2 control meals (rice or lactose-hydrolyzed milk). Results: The sum of breath-hydrogen concentrations for 8 h was significantl y greater (P < 0.005) after 34 g conventional soy (60.4 +/- 9.4 ppm) than a fter low-oligosaccharide soy (34.3 +/- 8.1 ppm). Greater differences were o bserved with 80-g doses: 157.9 +/- 19.4 ppm after conventional soy and 50.8 +/- 6.8 ppm after low-oligosaccharide soy (P < 0.001). Flatus frequency (7 .5 +/- 1.9 times/12 h) was significantly greater (P = 0.039) after ingestio n of 80 g conventional soy than after the control, rice meal (3.2 +/- 0.8 t imes/12 h), whereas flatus frequency after the low-oligosaccharide soy meal (3.9 +/- 0.7 times/12 h) was comparable with that after the rice meal. The re were no significant differences in the severity of other abdominal sympt oms. Conclusion: Soy flour derived from low-oligosaccharide soybeans resulted in less gas production than that derived from conventional soybeans.