title: Effects of Iron on Vitamin D Metabolism: A Systematic Review.
abstract: Vitamin D is a prohormone nutrient, which is involved in skeletal and extra-skeletal functions. Iron is another essential nutrient that is necessary for the production of red blood cells and oxygen transport. This element plays important roles in enzymatic systems including those required for Vitamin D activation. To the best of our knowledge, there is no exclusive review on the relationship between iron deficiency anemia (IDA), as the most prevalent type of anemia, and Vitamin D deficiency and the effect of recovery from iron deficiency on Vitamin D status. The aim of this study was to conduct a systematic search of observational and clinical trials in this field. The databases of PubMed, ProQuest, Cochrane Library, ISI Web of Knowledge, and SCOPUS were searched comprehensively. English-language human studies conducted on iron deficient patients or interventions on the effect of iron therapy on Vitamin D were extracted (n= 10). Our initial search yielded 938 articles. A total of 23 papers met the inclusion criteria. Thirteen studies were excluded because they were not relevant or not defining anemia types. The final analysis was performed on ten articles (3 cross-sectional and 7 interventional studies). Observational data indicated a positive relationship between iron status and Vitamin D, while trials did not support the effectiveness of iron supplementation on improving Vitamin D status. The mechanism underlying this association may involve the reduction of the activation of hydroxylases that yield calcitriol. Future randomized controlled trials with large sample sizes and proper designs are needed to highlight underlying mechanisms.
authors.affiliation: Department of Clinical Nutrition, School of Nutrition and Food Science, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Fatemeh
authors.initials: F
authors.lastname: Azizi-Soleiman
authors.affiliation: Department of Nutrition, School of Public Health, Iran University of Medical Sciences, Tehran, Iran.
authors.forename: Mohammadreza
authors.initials: M
authors.lastname: Vafa
authors.affiliation: Department of Nutrition, School of Public Health, Iran University of Medical Sciences, Tehran, Iran.
authors.forename: Behnaz
authors.initials: B
authors.lastname: Abiri
authors.affiliation: Department of Clinical Nutrition, School of Nutrition and Food Science, Isfahan University of Medical Sciences, Isfahan, Iran.
authors.forename: Morteza
authors.initials: M
authors.lastname: Safavi
keywords: Anemia; Vitamin D; Vitamin D deficiency; iron; iron-deficiency anemia