Vitamin D is believed to have many health benefits, including maintenance of bones, immune system and cardiovascular health. When the skin is exposed to ultraviolet rays, the body produces vitamin D. Most people are deficient in vitamin D, because technology and computer-centric work and activities make people often stay indoors. You can also get vitamin D from foods such as dairy products, sardines and eggs. Taking vitamin D supplements is an easy way to obtain this essential nutrient. Low vitamin D levels may be associated with depression symptoms. The imbalance of brain chemicals associated with depression is related to the increase in calcium ions (charged particles) in brain neurons. When the calcium ion content is high, it can prevent the release of certain neurotransmitters. Vitamin D can theoretically reduce the amount of calcium ions, thereby restoring the balance of neurotransmitters.