A composition comprising, preferably, at least partially defatted meal from a plant source containing protein-bound tryptophan that, preferably, has a higher tryptophan source than said plant source and a physiologically-acceptable diluent or carrier therefor for enhancing sexual desire and performance in a mammal. The composition, preferably, includes a carbohydrate. The invention provides a method of enhancing sexual desire and performance in a mammal having a composition described above.