The anal canal is UNSTRAIGHTENED when seated. Bowel evacuation when seated results frequently in OBSTRUCTIVE CONSTIPATION. Adopt a relaxed, FULL SQUAT POSTURE and the anal canal STRAIGHTENS.



Oncologists have observed that 80% of colon cancers occur in the caecum and the sigmoid colon, the two areas that are not fully evacuated in the sitting posture. This causes fecal stagnation and probably explains why colon cancer is the second leading cause of cancer deaths in the United States. In traditional Asian and African cultures where squatting is the norm, colon cancer is virtually unknown!

more:
http://www.naturesplatform.com/health_benefits.html
http://www.slate.com/articles/health_and_science/science/2010/08/dont_just_sit_there.single.html
http://www.relfe.com/toilet_seat_constipation.html