Yeast is a natural laxative. This is what you have to do to avoid the effect. Make sure the bottles are chilled for at least a couple days before you drink them. This will allow the yeast to settle out to the bottom of the bottle. Second, never drink from the bottle. The constant tipping back and forth shakes the yeast up. Always drink them from a glass and pour very slowly. Leave the last half inch of beer in the bottle. This should work wonders for you guys.