In a population of women with obesity, having insufficient blood concentrations of vitamin D was associated with increased markers of insulin resistance, signifying that low vitamin D and insulin resistance are both strongly associated with obesity, a new study published in the journal Nutrients found.
 
Vitamin D is one of several vitamins and minerals to which deficiency is associated with obesity based on prior research. Vitamin D deficiency is also established as having a direct impact on the production and signaling of insulin pathways, which may play a role in the development of insulin resistance, which is defined as a poor response to the hormone insulin which results in an increase in blood sugar and diabetes risk.
 
In the cross-sectional study, conducted between 2009 and 2013, blood samples were collected from 103 women who were diagnosed with obesity, and were enrolled and followed up with at an obesity clinic in the city of Salvador in Bahia, Brazil. Participants were stratified into three categories, Obesity I-III, and were assessed for their vitamin D levels as well as for markers of insulin resistance and diabetes diagnosis. The authors found that higher BMI had a direct and strong association with both vitamin D deficiency and HOMA-IR scores, which approximate the degree of insulin resistance based on fasting glucose and insulin concentrations.
 
“Vitamin D is a metabolite of huge clinical importance due to its interactions with calcium and the bone system in general,” the authors of the study noted. “In addition, many studies suggest that low levels of vitamin D are associated with increased frequency of immune disorders and other diseases, such as obesity. Importantly, obesity is a risk factor for hypovitaminosis D and is closely related to the development of other comorbidities: for example, fertility disorders and cardiovascular diseases, especially in women.”
 
The authors concluded that the pro-inflammatory status associated with obesity is likely the common link between vitamin D reductions and heightened HOMA-IR scores, which was backed by the pro-inflammatory profiles of participants with higher BMI.
 
“Importantly, chronic inflammation is also linked with the development of metabolic syndrome, which is a set of signs and symptoms that mark a higher cardiovascular risk and metabolic alterations, being related to low levels of vitamin D and is considered an important factor in increasing the morbidity and mortality of obese patients,” the authors of the study concluded, adding that while obesity had a strong link to reduced vitamin D, insulin resistance was also linked to low levels of vitamin D independently of obesity status.
 
Further studies are needed to assess the role that markers of immune function, and the pro- or anti-inflammatory responses associated with them, are needed in order to further establish mechanisms of action by which obesity can contribute to both vitamin D deficiency and insulin resistance in tandem.