Is the Association between Vitamin D and Metabolic Syndrome Independent of Other Micronutrients?

The incidence of metabolic syndrome (MetS) has been increasing globally and it is recognized as a major public health problem because MetS is associated with increased risk of diabetes, stroke, cancer, and other chronic diseases. Recently, MetS has been linked to vitamin D deficiency. However, the evidence on the association between vitamin D deficiency and the risk of MetS remains inconclusive. This review therefore aims to depict the existing evidence related to MetS and vitamin D deficiency, and examined some of the possible confounders which may affect the association between vitamin D status and risk of MetS. Earlier studies on the association between vitamin D deficiency and MetS have adjusted for the effect of some confounders including, age, sex, body mass index, race, physical activity, smoking, alcohol consumption, and energy intake. However, these studies failed to consider other potential confounders. There is evidence that vitamin A, zinc (Zn), and magnesium (Mg) play important roles in the activation and function of vitamin D and interact with gene expression. Furthermore, these micronutrients are also related to several components of the MetS including glucose intolerance, dyslipidemia, and obesity. Thus, there could be an interaction between these micronutrients, vitamin D, and MetS. This review highlights the possible interactions of vitamin A, Zn, Mg, and vitamin D with MetS and its components. The findings reinforce the need for further well-designed studies that take into account all potential confounders, including other micronutrients such as vitamin A, Zn, and Mg status, to investigate the independent association of vitamin D status with MetS and its components, and also to scrutinize for possible interactions among other nutrients which may have similar confounding effects.