**6. Prevalence of vitamin D deficiency**

Vitamin D receptors are traced throughout the brain explaining the role of vitamin D in psychosomatic disorders, and it was found to have an equivocal call for vitamin D deficiency and depression going hand in hand [12].

Vitamin D insufficiency/deficiency is a worldwide problem, affecting all ages and races. Optimal 25(OH) vitamin D concentrations for skeletal health are >30 ng/ml. Serum 25(OH) vitamin D concentrations are generally lower in blacks than in whites and people who avoid exposing them to the sun. The increased use of sunscreens is hypothesized to increase the prevalence of vitamin D deficiency. Older adults, as a result of hyperparathyroidism related to renal insufficiency, tend to require more vitamin D to achieve adequate levels of 25(OH) vitamin D. As a result of the change in the definition of adequate concentrations, the prevalence of vitamin D deficiency is higher than previously thought. The prevalence of vitamin D deficiency among older men and women living in the United States and Europe ranges from 40–100%. The National Health and Nutrition Examination Survey from 2000 to 2004 found that ~25% of men >50 years of age and 30–35% of women >50 years of age had 25(OH) vitamin D concentrations <0.001. Two studies performed in Colorado and Georgia found that despite reported consumption of more than the required daily intake of vitamin D (400–600 IU/d), the prevalence of vitamin D insufficiency (defined as <32 ng/mL and < 20 ng/ml, respectively) among community-dwelling older adults (mean age, 77.8 and 77.0 years, respectively) ranged from 36.7 to 74.0% [3].
