Optimum Nutrition provides a natural sleep aid so that you can get a full night of rest without waking up feeling groggy. If you are someone who tends to workout at night or just have trouble going to bed at a good time then Melatonin is the perfect sleep support supplement for you. Melatonin is a hormone produced by your body and secreted at night. Each serving of ON's Melatonin supplement provides 3 mg of pure melatonin along with 72 mg of calcium and 55 mg of phosphorus.