The Need to Standardize Vitamin D Dosage in Dietary Supplements

We read with great interest the article by Domański et al. describing the results of an analysis concerning vitamin D content in dietary supplements available in EU countries [1]. In our opinion, the article raises a very important issue, which is the lack of regulated standardization of dietary supplements in terms of the contained doses of vitamin D. Recent data collected during a large observational study report that about 40% of Europeans are vitamin D deficient, and 13% are severely deficient [2]. A significantly reduced vitamin D level can cause serious metabolic disorders, leading to deregulation of calcium-phosphate metabolism, increased risk of infections, endocrine disorders, or increased risk of depression. With increasing public awareness of the potential consequences of vitamin D deficiency, the use of vitamin D-containing supplements has been steadily increasing in recent years [2,3].