Role of Vitamin D in Obesity

Abstract

Hypovitaminosis D and obesity represent global public health problems. Plasma concentrations of 25 (OH) D are more strongly correlated with visceral adipose tissue than subcutaneous fat, suggesting a link between vitamin D levels, insulin resistance and cardiometabolic risk, particularly in younger subjects. Various studies have shown that obesity is an important risk factor for vitamin D deficiency and how adiposity has a determining role in the serum level of vitamin D. The association between these two factors is complex and the multiple studies carried out to clarify this association have not provided univocal indications. Some hypotheses propose that the deficiency of vitamin D may remain a cause of obesity. However, the possible pathophysiological mechanisms do not exclude a multifactorial origin, thus supporting the importance of supplementing vitamin D in obese patients. Since adipose tissue is a major reserve of vitamin D, its role in the regulation of adipogenesis, insulin sensitivity, and in the reduction of cytokine release and adipose tissue inflammation has been demonstrated. Moreover, studies on the vascular effect of vitamin D have been carried out. This review attempts to summarize the current understanding regarding the causes of the reduced vitamin D levels in obese patients, the effects of vitamin D supplementation in these individuals, and the prevention of the complications associated to obesity such as the chronic inflammatory state and vascular complications which predispose to cardiovascular risk.