Pistachios A Natural Source of Melatonin Pistachios Are a Natural Source of Melatonin. How Well Does it Work? A surprising discovery is that several plants and herbs are natural sources of melatonin, a hormone produced in the pineal gland. Pistachios are one of these natural sources. Melatonin is widely used to support healthy sleep. This study compared a pistachio-derived melatonin supplement with a synthetic melatonin supplement, with both groups receiving 1 mg of melatonin. Researchers found that pistachio-derived melatonin was absorbed