Milk naturally contains melatonin and drinking a warm glass of milk before bed can help you to sleep better and impacts melatonin levels. Pistachios as well as other nuts such as almonds and cashews also contain melatonin. However, out of all the nuts, pistachios contain the most melatonin. Other foods that contain melatonin include goji berries, rice, tart cherries, mushrooms, fatty fish, oats etc. Melatonin supplements obviously have a stated dose, as do all types of dietary supplements for healthy adults, which makes the amount you get easier to calculate.