The multitude of factors that affect vitamin D synthesis by the skin 14, the most important of which is degree of skin pigmentation, make it difficult to determine what is adequate sunshine exposure for any given infant or child 15, 16. These factors include the amount of skin pigmentation, body mass, degree of latitude, season, the amount of cloud cover, the extent of air pollution, the amount of skin exposed, and the extent of UV protection, including clothing and sunscreens 11 – 13. The amount of UV exposure available for the synthesis of vitamin D depends on many factors other than just time spent outdoors. Full-body exposure during summer months for 10 to 15 min in an adult with lighter pigmentation will generate between 1000 IU of vitamin D 3 within 24 h individuals with darker pigmentation require 5 to 10 times more exposure to generate similar amounts of vitamin D 3 9, 10. Historically, the main source of vitamin D has been via synthesis in the skin from cholesterol after exposure to UV-B light. The second clinical presentation was that of a more chronic disease, with rickets and/or decreased bone mineralization and either normocalcemia or asymptomatic hypocalcemia. The first was symptomatic hypocalcemia (including seizures) occurring during periods of rapid growth, with increased metabolic demands, long before any physical findings or radiologic evidence of vitamin D deficiency occurred. Two types of presentation of vitamin D deficiency have been described in children 8. A state of deficiency occurs months before rickets is obvious on physical examination, and the deficiency state may also present with hypocalcemic seizures 6, growth failure, lethargy, irritability, and a predisposition to respiratory infections during infancy 7. Rickets is an example of extreme vitamin D deficiency, with a peak incidence between 3 and 18 months of age. Rickets attributable to vitamin D deficiency is known to be a condition that is preventable with adequate nutritional intake of vitamin D 5. There is evidence that the current supplementation recommendations, particularly for pregnant and lactating women, are inadequate to ensure vitamin D sufficiency in these groups. Despite food fortification policies in many countries and recommendations for vitamin D supplementation of at-risk groups, vitamin D deficiency and infantile rickets remain major public health challenges in many developed and developing countries. Prevention of vitamin D deficiency and achieving adequate intake of vitamin D and calcium throughout childhood may reduce the risk of osteoporosis as well as other long-latency disease processes that have been associated with vitamin D-deficiency states in adults 1 – 4. In fact, more and more scientific evidence linking vitamin D to various chronic diseases in children and adults is emerging. There has been increasing global interest regarding the role of vitamin D in health and disease.
0 kommentar(er)
