Vitamin A deficiency has been a cause of impotence in some men. Vitamin A! "Vitamin A deficiency has been the trigger of impotence in some men," states Elson Haas, M.D., Director of the Preventive Medical Middle. Much more frequently than not Erectile Dysfunction is short-term. Muira Puama for instance helps a man have harder erections and increased libido simply because it is considered a nerve stimulant.