3. Vitamin D
The body can make small amounts of Vitamin D when exposed to sunlight. However, if you stay out of the sun and avoid eating foods with Vitamin D, you can develop a deficiency to this vitamin. Vitamin D is linked to nerve and brain function. A lack of vitamin D can damage the immune system as well. Also, low levels of Vitamin D can lead to depression, anxiety, and fatigue. Other problems that are caused by a Vitamin D deficiency are sleeping troubles, weakness, somatic complaints and weight gain.