The Chinese say oolongs get your stomach going, whereas pu'er strengthens your digestive system, and this has largely proven true. Oolongs stimulate your metabolism and alkalise your digestive tract, helping to balance the acids that break down food. Aged pu'ers, because they undergo microbial fermentation, contain a number of beneficial enzymes that can address ailments from constipation to Irritable Bowel Syndrome. (IBS). Both help lower cholesterol.