compositions are described comprising at least partially defatted meal from a plant source containing protein - bound tryptophan , preferably squash seeds , and , optionally , a carbohydrate source provided in an amount capable of facilitating transport of in vivo generated tryptophan across the blood brain barrier . also described are dietary supplements , foods and beverages comprising the composition of the invention to induce sleep or provide tryptophan supplementation to individuals in need thereof .