Magnesium has been found to reduce symptoms of insomnia as it encourages relaxation. Further to this, it has also been found to reduce the amount of cortisol (stress hormone) in the body, which is a common reason for a sleepless night. Deficiency in the nutrient also leads to insomnia and the inability to remain asleep. Magnesium is also important for the absorption of calcium. It can be found in dark chocolate, avocado, nuts, legumes, tofu, seeds, salmon, wholegrains, mackerel and bananas.