The main side effect of beans is Flatulence. Many varieties of beans, including flat beans contain oligosaccharides (particularly raffinose and stachyose), a type of sugar molecule also found in cabbage. An anti-oligosaccharide enzyme is necessary to properly digest these sugar molecules. The normal human digestive tract does not contain or produce any anti-oligosaccharide enzymes. So, the consumed beans containing oligosaccharides are typically digested by bacteria in the large intestine. This digestion process produces gases, which are then released as flatulence.