Approximately 77% of the population have vitamin D deficiency. Among other functions, vitamin D is involved in calcium homeostasis, ion channel function, as well as dopamine and serotonin levels in the brain. Additionally, vitamin D helps to decrease inflammation in the body through its role in regulating the microbiome. Psychological disorders such as depression, anxiety, and schizophrenia are associated with low vitamin D levels in the body. The supplementation of vitamin D to those with vitamin D deficiency has been successful in alleviating anxiety in interventional studies. Supplementing with vitamin D appears to only be effective in reducing anxiety for those who are deficient in vitamin D. However, there is a persistent deficiency of vitamin D in the population, and for most people, dietary or sun exposure alone are not enough to meet adequate vitamin D requirements.