Vitamin D deficiency in children and adolescents; an international challenge

Vitamin D deficiency in the world Low vitamin D level is an important international public health problem (1-3). Vitamin D deficiency and its consequences among children and adolescents could indeed be considered as one of the most important problems. In fact, low vitamin D levels were reported in both children (4), especially obese children (5), and adolescents. For example, in a study, 9.9% of Korean adolescents had vitamin D deficiency (6). This deficiency was also common in Kuwait (7), Italy (2,8), Norway (9), Oslo (10), India (3), Japan (11) and the Netherlands (12). In addition, Palacios et al., in a systematic review on world situation of vitamin D deficiency, from April to June 2013, found out that vitamin D deficiency could be considered as an international public health problem, especially in the Middle East area (1). More importantly, many countries in developing world, are experiencing a substantial percentage of adolescent and youth population with their own health related problems which could affect on their health (13). Several reasons could be taken into account in this regard such as the possibility of the reduced intake or synthesis of vitamin D (due to having a vitamin D deficient mother or a dark skin color), abnormal intestinal function, malabsorption, reduced synthesis or increased degradation of vitamin D (in chronic liver or renal disease) (14). Valtueña et al. investigated vitamin D deficiency among European adolescents and reported that many factors could affect on vitamin D deficiency such as season, latitude, fitness, adiposity, sleep time and vitamin D supplement intake (15). Additionally, Oberg et al. studied on different factors related with vitamin D deficiency in Norwegian Adolescents (9). They found out a significant sex difference, the snuff usage, vitamin D fortified milk intake, using the cod liver oil and vitamin/mineral supplements, physical inactivity, taking a sunbathing holiday and usage of solarium in both school boys and girls. They also detected an inverse correlation between parathyroid hormone levels with vitamin D deficiency among adolescents. Moreover, in Italian healthy adolescents, the prevalence of vitamin D deficiency was about half of participants in the study of Abstract Low vitamin D level is an important international public health problem. Vitamin D deficiency and its consequences among children and adolescents could indeed be considered as one of the most important public health problems. In fact, low vitamin D levels were reported in both children and adolescents. Several reasons could be taken into account in this regard such as the possibility of the reduced intake or synthesis of vitamin D (due to having a vitamin D deficient mother or a dark skin color), abnormal intestinal function or malabsorption (in small-bowel disorders), or reduced synthesis or increased degradation of vitamin D (in chronic liver or renal disease). More importantly, many countries in developing world, are experiencing a substantial percentage of adolescent and youth population with their own health related problems which vitamin D deficiency could affect on their health. The association between obesity and overweighting and vitamin D deficiency has been reported by many researchers. Diabetes mellitus has also an association with vitamin D deficiency, for both type 1 and type 2 diabetes. Due to the importance of vitamin D deficiency and its negative health consequences, taking the vitamin D supplement seems to be necessary.