Groundbreaking new research published in the Journal of Clinical Endocrinology & Metabolism suggests that people with low vitamin D levels are more likely to have diabetes, regardless of how much they weigh.
Studies have consistently found that vitamin D deficiency is associated with obesity and diabetes. Though, most research that has evaluated the relationship between vitamin D status and body mass index (BMI) has failed to consider if patients were diabetic or not.
Since the majority of obese patients have altered sugar metabolism, researchers from the current study questioned whether vitamin D deficiency is directly related to obesity, or rather, a consequence of altered sugar metabolism, such as diabetes.
In order to answer this question, the researchers looked at the vitamin D levels of individuals with a wide range of BMI values, taking into account whether the patients were pre-diabetic, diabetic, or neither.
They studied participants from two cohorts. Cohort 1 consisted of 118 participants recruited from the University Hospital in Malaga, Spain, all of whom were classified based on their BMI. Cohort two was comprised of 30 obese patients who were recruited from the University Hospital in Girona, Spain.
The researchers measured vitamin D blood levels of each participant and the levels of vitamin D receptors in their fat tissue. Then, they compared the presence of diabetes, pre-diabetes, and normal blood sugar to vitamin D levels according to each BMI classification.
BMI is calculated based on height and weight. BMI is categorized as follows,
- < 18.5: underweight
- 18.5 – 24.9: normal weight
- 25 – 29.9:overweight
- 30 or greater: obese
Here is what the researchers found:
- Obese participants without diabetes, prediabetes, or any sign of an altered sugar metabolism had significantly higher vitamin D levels than their diabetic peers (p < 0.05).
- Lean participants without diabetes, prediabetes, or any sign of an altered sugar metabolism had significantly higher vitamin D levels than their diabetic peers (p < 0.05).
- Vitamin D levels were negatively correlated with insulin resistance and blood glucose (p = 0.032 and 0.001, respectively), but not with BMI.
- Vitamin D receptor gene expression was higher in morbidly obese than in other BMI groups (p < 0.05).
The researchers stated,
“In conclusion, 25(OH)D levels showed a close relationship with variables related to glucose metabolism, suggesting that VD deficiency is associated more with carbohydrate metabolism than with obesity.”
In a press release, researcher Manuel Macías-González of the University of Málaga stated,
“The study suggests that vitamin D deficiency and obesity interact synergistically to heighten the risk of diabetes and other metabolic disorders,”
The study is noteworthy due to it being the first cross sectional study to compare vitamin D levels between a wide range of BMI values while taking into account whether the subjects were pre-diabetic, diabetic, or had normal blood glucose. However, it’s important to note that this study does not prove causality and only shows an association.
Future studies should be designed to prospectively look at the relationship between vitamin D, obesity, and diabetes in a cohort.
Clemente-postigo M., et al. Serum 25-Hydroxyvitamin D and Adipose Tissue Vitamin D Receptor Gene Expression: Relationship With Obesity and Type 2 Diabetes. Journal of Clinical Endocrinology & Metabolism, 2015.