Teas made from dried mango leaves are used as a treatment for type 2 diabetes in Indian folk medicine, and also in the herbal healing traditions of sub-Saharan western
Africa. The research is still being conducted on animals, not people, but there are indications that a chemical called 3-beta-taraxerol in mango leaf makes liver cells and fat cells more sensitive to insulin, helping them take sugar out of the bloodstream--without the nasty side effect of creating more fat cells, like Actos or Avandia. Don't run to some tropical destination just to get mango leaves, but be on the lookout for more and more products based on mango leaf to enter the market over coming years.
Sangeetha KN, Sujatha S, Muthusamy VS, Anand S, Nithya N, Velmurugan D, Balakrishnan A, Lakshmi BS. 3beta-taraxerol of Mangifera indica, a PI3K dependent dual activator of glucose transport and glycogen synthesis in 3T3-L1 adipocytes. Biochim Biophys Acta. 2010 Mar;1800(3):359-66. Epub 2009 Dec 21.