It has proven its use as an antidiarrheal. Quercetin found in leaves are responsible for this action on the system (Echemendia, 2004)
It is best to use leaf tincture to 20% in order to get results.
Echemendia, C, 2004.Tinturas Psidium guajava leaf L. in patients with simple acute diarrhea. Retrieved on January 18, 2012. http://scielo.sld.cu/scielo.php?pid=S1028-47962004000300008&script=sci_arttext&tlng=pt