With LIDTKE L-Tryptophan, USP, there really is no better, no more-natural way to feel relaxed. Tryptophan is a natural building block of serotonin, the neurotransmitter that plays an important role in appetite, mood, normal sleep patterns and nervous-system function. Serotonin has become a goldmine for the makers of patent ingredients, but there are two vastly different approaches to making your body think it has more serotonin: one is to mimic it, the other is to make it. This product contains no added gluten, yeast, wheat, soy, milk, dairy products, eggs, nuts, tree nuts, peanuts, fish, shellfish, sugar, preservatives, artificial color or artificial flavor. Non-GMO.