ABSTRACT
Vitamin D deficiency has been shown to affect iron status via decreased calcitriol production, translating to decreased erythropoiesis. The present study aimed to determine for the first time whether vitamin D supplementation can affect iron levels among Arab adolescents. A total of 125 out of the initial 200 Saudi adolescents with vitamin D deficiency (serum 25(OH)D < 50 nmol/L) were selected from the Vitamin D-School Project of King Saud University in Riyadh, Saudi Arabia. Cluster randomization was done in schools, and students received either vitamin D tablets (1000 IU/day) (N = 53, mean age 14.1 ± 1.0 years) or vitamin D-fortified milk (40IU/200mL) (N = 72, mean age 14.8 ± 1.4 years). Both groups received nutritional counseling. Anthropometrics, glucose, lipids, iron indices, and 25(OH)D were measured at baseline and after six months. Within group analysis showed that post-intervention, serum 25(OH)D significantly increased by as much as 50%, and a parallel decrease of -42% (p-values <0.001 and 0.002, respectively) was observed in serum iron in the tablet group. These changes were not observed in the control group. Between-group analysis showed a clinically significant increase in serum 25(OH)D (p = 0.001) and decrease in iron (p < 0.001) in the tablet group. The present findings suggest a possible inhibitory role of vitamin D supplementation in the iron indices of healthy adolescents whose 25(OH)D levels are sub-optimal but not severely deficient, implying that the causal relationship between both micronutrients may be dependent on the severity of deficiency, type of iron disorder, and other vascular conditions that are known to affect hematologic indices. Well-designed, randomized trials are needed to confirm the present findings.
Subject(s)
Arabs , Iron/blood , Vitamin D/administration & dosage , Adolescent , Adolescent Nutritional Physiological Phenomena , Animals , Calcitriol/physiology , Cohort Studies , Dietary Supplements , Female , Food, Fortified , Health Education , Humans , Iron/analysis , Iron Deficiencies , Male , Milk , Nutritional Status/physiology , Saudi Arabia , Vitamin D/analogs & derivatives , Vitamin D/blood , Vitamin D Deficiency/physiopathologyABSTRACT
BACKGROUND: Both childhood obesity and vitamin D deficiency are common in the Middle East. This study aims to determine whether the associations of vitamin D status to traditional anthropometric parameters hold true for nonconventional measures of adiposity, such as body adiposity index (BAI), a measure of body fat percentage, waist-to-hip ratio, waist-to-height ratio (WHtR), and lipid indices, in apparently healthy Arab children. METHODS: A total of 4183 apparently healthy Saudi school students (1906 boys; 2277 girls) aged 12 to 17 years were recruited in this cross-sectional study. Anthropometrics were obtained. Fasting blood glucose and lipids were measured routinely. Serum 25(OH)D was measured using chemiluminescence. RESULTS: In all subjects, age, BAI, waist-to-hip ratio, and high-density lipoprotein cholesterol (HDL-C) accounted for 4% of the variance in serum 25(OH)D (P < .001). All adiposity indices were inversely associated with 25(OH)D, with WHtR being the most inferior in terms of strength of association. Vitamin D deficiency significantly increased risk for low HDL-C in all subjects (odds ratio [95% confidence interval]: 1.70 [1.24-2.3]; P < .001). CONCLUSION: BAI is significantly associated with 25(OH)D levels in Arab children. WHtR is inferior than other anthropometric measures of obesity regarding the strength of association with 25(OH)D. Risk for or low HDL-C is significantly increased with vitamin D deficiency. Interventional studies may determine the potential cardioprotective effects of vitamin D correction in this population.
