The objective of the study was to compare gas production and gaseous symptoms in healthy volunteers after ingestion of 34 and 80 g soy flour made from either conventional soybeans or soybeans naturally low in indigestible oligosaccharides.
Design: In a double-blind, randomized, crossover protocol, breath hydrogen (an indicator of carbohydrate malabsorption), flatus frequency, and abdominal symptoms were assessed after subjects ingested the soy products and after 2 control meals (rice or lactose-hydrolyzed milk).
Results: The sum of breath-hydrogen concentrations for 8 h was significantly greater (P < 0.005) after 34 g conventional soy (60.4 ± 9.4 ppm) than after low-oligosaccharide soy (34.3 ± 8.1 ppm). Greater differences were observed 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 ingestion of 80 g conventional soy than after the control, rice meal (3.2 ± 0.8 times/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. There were no significant differences in the severity of other abdominal symptoms.
Conclusion: Soy flour derived from low-oligosaccharide soybeans resulted in less gas production than that derived from conventional soybeans.