Vitamin D Supplementation Modestly Reduces Serum Iron Indices of Healthy Arab Adolescents

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.

The Role of Polymorphisms in Vitamin D-Related Genes in Response to Vitamin D Supplementation

“…Several factors have been shown to contribute to vitamin D deficiency, including low skin exposure to sunlight, low dietary intake of vitamin D, high body mass index (BMI), genetic predisposition, the gut microbiome, and the immune system [ 7 , 8 , 9 , 10 , 11 ]. The Middle East regions are also affected by vitamin D deficiency [ 3 , 12 , 13 , 14 ]. In fact, despite having ample sunshine, these regions register the highest rate of vitamin D deficiency [ 13 ].…”

“…This is partially explained by the limited sun exposure due to cultural practices. Other common risk factors in these regions include female gender and clothing style, multiparity, sedentary lifestyle, and low intake of vitamin D and calcium from the diet [ 14 , 15 ].…”

The association between iron and vitamin D status in Arab adolescents

“…Among the limited interventional studies on healthy participants, cholecalciferol (vitamin D 3 ) supplementation showed a downward but non-significant change in the levels of serum Fe, serum ferritin, Hb and TSAT among 251 adult ethnic minorities in Norway (26) . Furthermore, the longest interventional study on the effects of vitamin D supplementation on Fe indices was recently conducted in the present cohort of Arab adolescents with suboptimal vitamin D and revealed a modest but significant decrease in levels of Fe and TIBC, parallel to the increase in vitamin D status (19) .…”

“…In brief, more than 1000 apparently healthy students were recruited from the different government schools in Riyadh, Saudi Arabia to ascertain the effects of several vitamin D correction strategies including sunlight exposure, oral supplementation and vitamin D-fortified diets (13,14) . All participants, despite coming from different schools, were selected from the same geographical location and have the same environmental conditions, as described previously (19) . Participants completed a questionnaire on past medical history, general health status and demographic information.…”

Dietary Trace Minerals

“…The manuscripts in this Special Issue collection include populations from many countries, including the USA, Germany, Australia, Brazil, Poland, Japan, Colombia, Mexico, Saudi Arabia, Russia, Italy, South Korea, and Israel. The presented manuscripts cover a wide variety of topics in the field of dietary trace minerals, with emphasis on the antimicrobial properties of magnesium and the potential to develop healthier food [1], the link between Nrf2 and dietary selenium, iron, zinc, and copper [2], in vivo assessment of fast cooking yellow bean consumption on dietary iron bioavailability [3], the association between nicotianamine and 2′ deoxymugineic acid as enhancers of iron bioavailability in vitro [4], analysis of bioelectrical impedance vector and phase angle on various forms of oral zinc supplementation in children [5], investigation of dietary silicon and its impact on plasma silicon concentrations in human subjects [6], the role of biotin in skin zinc homeostasis [7], the maize germ fraction and its inhibitory effect on iron bioavailability in vitro [8], assessment of the iron bioavailability of iron-biofortified beans in school children [9], investigation of the dietary iron bioavailability of iron biofortified carioca beans in vivo [10], vitamin D supplementation and its effect on serum iron concentrations in adolescents [11], the demonstration of silver ions as a tool for understanding copper metabolism [12], and the dietary and sentinel potential factors that lead to hemochromatosis [13]. This wide spectrum of topics further demonstrates the importance and relevance of dietary trace minerals, as these factors are critical and have a pivotal role in organism (including human) health and physiological functions.…”