Effect of dietary calcium intake on vitamin D levels and obesity in Saudi children

The drastic changes in lifestyle and nutrition brought about by rapid economic changes in Saudi Arabia have seriously threatened the health with emergence of a number of chronic non-communicable diseases. Obesity, which is a major contributing factor in the emergence of these diseases – cancers, type 2 diabetes and hypertension - has increased rapidly worldwide and especially in Saudi Arabia. While several risk factors have been identified, one micronutrient deficiency stands not only because of its equally alarming global prevalence, but also because of its multiple physiologic roles that influence normal metabolic functioning. Vitamin D deficiency has been linked to several chronic diseases in adults, and almost all cardiometabolic risk factors are associated with vitamin D deficiency in both adults and children. Studies focusing on children and adolescents however, are limited. This randomized cross sectional study aimed to determine the prevalence of vitamin D deficiency and its association with childhood obesity among a population of healthy Saudi boys and girls in Riyadh city, Saudi Arabia. Furthermore, this study was aimed to determine whether levels of dietary calcium can explain the high prevalence of low-vitamin D levels in Saudis, and whether these dietary micronutrients influence risk of obesity. To achieve this, 331 Saudi boys and girls (53.8% females and 46.2 % males) aged 6-18 years were randomly recruited from primary care health centers in different areas of Riyadh city. Demographic, medical and dietary information was collected from each subject using a questionnaire. Anthropometrics were measured. Blood levels of fasting glucose, lipid profile, 25(OH) D and corrected calcium were measured routinely, 25(OH) D was quantified using enzyme-linked immunosorbent assay (ELISA). The present study demonstrated that around 100% of the subjects were either mildly or moderately or severely vitamin D deficient, with girls having significantly lower vitamin D levels than boys in both preadolescents and adolescents. Moreover, adolescent were more deficient than preadolescent. Serum vitamin D levels showed an inverse significant association with BMI, fat mass percentage, body fat mass, TG, waist circumference and hip circumference. Calcium intake did not find significant associations with either obesity or vitamin D deficiency. Although the average calcium intake of the sample is low and mean vitamin D level for the sample is deficient. The serum corrected calcium was positively correlated with vitamin D serum and negatively correlated with BMI, fat mass and waist to hip ratio. The corrected serum calcium was significantly lower in girls compared to boys in the adolescent group, similar to vitamin D level. Also, approximately 30 % of the subjects with <250 mg of calcium daily were obese, while only 14 % of the subjects with >800 mg of calcium intake were obese. Interestingly, serum vitamin D was highest in the heavy consumer group for both tea and coffee. Also, BMI mean value was significantly decreased in increased drinkers (9-12 times/week) when compared to low and moderate drinkers. The lowest levels of vitamin D and the highest value of BMI fell in the group with no physical activity. This study highlights the need for vitamin D correction even in this age group where chronic diseases are not expected. This can be achieved by encouraging not only an active and outdoor lifestyle, but by proper nutrition in which micronutrients such as vitamin D and calcium are taken into account