The purpose of the present study is to establish the effect of the yacon tuber and leaf (Smallantus Sonchifolius) on the levels of the seric glucose and glycosylated hemoglobin with the consumption of an adlibitum diet. A blind, simple and experimental field-controlled trial was carried out for a period of 90 days in 30 subjects, in an age range from 26 to 90, who were diagnosed with Type 2 Diabetes Mellitus with no control despite the pharmacological treatment. The subjects were divided into 3 groups; the first group received 500g per day of fresh yacon fruit; the second group received freeze-dried yacon equivalent to 500 g per day of the fresh fruit, and the third group received yacon leaves tea bags (each tea bag containing the equivalent to 1 g of yacon leaves), which were taken three times a day.Regarding the glycosylated hemoglobin, the administration of the fruit, the tea bags and...