Studies show that yohimbe, a tree bark extract, has been shown to increase blood flow to the penis.
In clinical tests, the active ingredient in yohimbe was tested on a group of men who had been impotent for less than two years. A landmark strictly-controlled Canadian study in the 1980s showed that the active ingredient in yohimbe could be a significant aid to restoring potency in diabetic and heart patients who often are prey to impotence. The yohimbe extract triggers chemical changes in the body that can also aid psychogenic cases of impotence, due predominantly to fatigue, tension and stress. In a 1994 Italian clinical study, half the patients received the active tablets for eight weeks and half received placebos. Something in yohimbe, then, obviously stimulates the male libido.