Among the leading causes of under 5 mortality andmorbidity in Bangladesh, Acute respiratory infections(ARI) are at the top of the list .These are a major cause ofglobal mortality and morbidity and are responsible for 10%of ambulatory and emergency department visits in the1USA and an estimated 2.65 million deaths worldwide in22013 . Observational studies report consistent independentassociations between the low serum concentrations of 25-hydroxyvitamin D (the major circulating Vitamin Dmetabolite) and susceptibility of acute respiratory tract3,4infections . This Article highlights the indication ofvitamin D supplementation in the prevention of acuterespiratory Infection.

Vitamin D, or the “sun-shine vitamin”, is not just as avitamin; it is also prohormone with numerous functions in5the body . ”Prohormone “refers to a group of fat solubleseco-steriods. The best-understood function of Vitamin Dis in the absorption of calcium from the small intestine,which helps to prevent diseases such as rickets in children6and osteoporosis and osteomalacia in adults . In addition tocausing rickets, vitamin D deficiency has been linked torespiratory infection such as tuberculosis and Bronchiolitis7along with pneumonia . The effects of Vitamin D aremediated by a cytosolic receptor called Vitamin D Receptor(VDR). VDR is ubiquitously expressed, and this ubiquityaccounts for the numerous and varied mechanisms that are8regulated by vitamin D . The VDR gene, which is locatedon chromosome 12q13.1, has several polymorphic regions,some of which are associated with predisposition of certaindiseases. This means that not only is vitamin D deficiency isassociated with considerable risk of diseases, but there iswide interindividual variation in vitamin D sensitivity,9which may influence risk