en Nutrition Nutrition Review Review <span style="font-size:10pt"><span style="unicode-bidi:embed"><span style="font-family:&quot;Times New Roman&quot;,&quot;serif&quot;">Vitamin D was identified over one hundred years ago, yet vitamin D deficiency (VDD) is still the most prevalent nutritional problem all around the world. The National Food and Nutrition Surveillance together with other reports have documented alarming rates of VDD and its possible adverse consequences in both children and adults in Iran. However, the prevalence rates of VDD reported by various research groups show a wide range. In this short review, we discuss some of the main causes of these discrepancies and propose some strategies to minimize them. Finally, some key recommendations for future studies and combating VDD are presented for policymakers.</span></span></span><br> <br> <span style="font-size:10pt"><span style="line-height:110%"><span style="tab-stops:409.5pt"><span style="unicode-bidi:embed"><span style="font-family:&quot;Times New Roman&quot;,&quot;serif&quot;"><b><span style="font-size:12.0pt"><span style="line-height:110%"><span style="font-family:&quot;Arial Black&quot;,&quot;sans-serif&quot;"><span style="color:#c0504d">Highlights:</span></span></span></span></b></span></span></span></span></span> <ul> <li style="margin-bottom:11px"><span style="font-size:10.0pt"><span style="line-height:115%"></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:&quot;Times New Roman&quot;,&quot;serif&quot;">Vitamin D deficiency (VDD) is a global health problem and Iran is no exception. Nevertheless, the prevalence rates of VDD reported by various research groups show a wide range.</span></span></span></li> <li style="margin-bottom:11px"><span style="font-size:10.0pt"><span style="line-height:115%"></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:&quot;Times New Roman&quot;,&quot;serif&quot;">To have a better picture of vitamin D status in the community, standardization of definitions of vitamin D status and laboratory methods is necessary.</span></span></span></li> <li style="margin-bottom:11px"><span style="font-size:10.0pt"><span style="line-height:115%"></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:&quot;Times New Roman&quot;,&quot;serif&quot;">One approach to minimize inter-method variations of 25(OH)D assay is harmonization.</span></span></span></li> <li style="margin-bottom:11px; text-align:justify"><span style="font-size:10.0pt"><span style="line-height:115%"></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:&quot;Times New Roman&quot;,&quot;serif&quot;">Using any method to assay circulating 25(OH)D, VDD prevalence rate of 50 percent and above is undoubtedly a major health problem and necessitates prompt intervention.</span></span></span></li> <li style="text-align:justify"><span style="font-size:10.0pt"><span style="line-height:115%"></span></span><span style="font-size:10.0pt"><span style="line-height:115%"><span style="font-family:&quot;Times New Roman&quot;,&quot;serif&quot;">Vitamin D fortification of flour is an effective strategy to improve vitamin D status of the community but must be examined in a pilot study.</span></span></span></li> </ul> Vitamin D, Vitamin D deficiency, 25-hydroxycalciferol, 25(OH)D, Food fortification 1 6 http://nfsr.sbmu.ac.ir/browse.php?a_code=A-10-43-5&slc_lang=en&sid=1 Bahareh Nikooyeh 10031947532846006300 10031947532846006300 No Laboratory of Nutrition Research, National Nutrition and Food Technology Research Institute and School of Nutrition Science and Food Technology, Shahid Beheshti University of Medial Sciences, Tehran, Iran Tirang R. Neyestani neytr@yahoo.com 10031947532846006301 10031947532846006301 Yes Laboratory of Nutrition Research, National Nutrition and Food Technology Research Institute and School of Nutrition Science and Food Technology, Shahid Beheshti University of Medial Sciences, Tehran, Iran