Worldwide vitamin D status

Vitamin D status and the prevalence of vitamin D deficiency and insufficiency have been addressed in many studies covering all continents. Vitamin D deficiency, defined as a serum 25-hydroxyvitamin D lower than 25 nmol/L, occurs in risk groups all over the world, mainly in the Middle East, China, Mongolia, and India. Risk groups for poor vitamin D status are young children especially those with low birth weight, adolescents, pregnant and lactating women, older persons, and non-Western immigrants. A vitamin D status can be considered adequate (serum 25-hydroxyvitamin D > 50 nmol/L) in less than 50% of the world population at least in winter. Prevention of vitamin D deficiency requires moderate sunlight exposure, consumption of fish, fortification of foods with vitamin D, and the use of vitamin D supplements.