Currently, in medical circles, vitamin D is the talk of the town.
Produced in our skin on contact with sunlight, it plays a myriad of roles in the human body.
In the past few months, Medical News Today have covered a wealth of research into the group of fat-soluble secosteroids more commonly known as vitamin D.
With more than 40 percent of the population of the United States being vitamin D deficient, this is a serious issue. Some authors have referred to it as "an ignored epidemic," estimating that over 1 billion people worldwide have inadequate levels.
Understanding vitamin D deficiency
As vitamin D's importance becomes ever clearer, researchers are dedicating more and more time to understanding who might be most at risk of deficiency and working out ways to prevent it.
Because the vitamin appears to play a part in so many conditions, addressing the deficiency issue could have a considerable impact on the population at large.
One group of researchers investigating this topic hails from the VU University Medical Center and Leiden University Medical Center, both in the Netherlands. Led by Rachida Rafiq, they recently presented their findings at the European Society of Endocrinology annual meeting, held in Barcelona, Spain.
A link between obesity and lower vitamin D levels has previously been spotted. Rafiq and team dug a little deeper; they set out to understand whether the type and location of fat played a role. To do this, they took data from the Netherlands Epidemiology of Obesity study, including thousands of men and women aged 45–65.
The team focused on total fat, abdominal subcutaneous adipose tissue (belly fat under the skin), visceral adipose tissue (around the organs), and hepatic fat (in the liver).
During their analysis, they adjusted the data for a range of potentially confounding variables, such as alcohol intake, smoking, ethnicity, education level, chronic disease, and physical activity levels.
Vitamin D and belly fat exposed
They discovered that in women, both total and abdominal fat were associated with lower vitamin D levels, but that abdominal fat had the greatest impact. In men, however, lower vitamin D levels were significantly linked with fat in the liver and abdomen.
Across both sexes, more belly fat predicted lower levels of vitamin D.
Rafiq explains, "[T]he strong relationship between increasing amounts of abdominal fat and lower levels of vitamin D suggests that individuals with larger waistlines are at a greater risk of developing deficiency, and should consider having their vitamin D levels checked."
Her next step is to understand why this relationship exists. Does a deficiency in vitamin D cause fat to be stored in the abdominal region, or does belly fat decrease levels of vitamin D? It will take more work to tease apart cause and effect.
As Rafiq explains, "Due to the observational nature of this study, we cannot draw a conclusion on the direction or cause of the association between obesity and vitamin D levels."
"However, this strong association may point to a possible role for vitamin D in abdominal fat storage and function."
The links between obesity and vitamin D deficiency are growing increasingly robust. The next challenge is working out a way to effectively tackle this issue.