Too little of the "sunshine vitamin" -- vitamin D -- in Black Americans could raise their odds of developing diabetes, new research suggests.
Two new studies found an association between levels of vitamin D in the blood and insulin resistance, a precursor to full-blown diabetes.
It's been long known that low blood levels of vitamin D "are associated with an increased risk of diabetes in white populations, but our research strongly suggests that this relationship also holds true for African Americans," said Amaris Williams, a co-author on both studies and a postdoctoral scholar in the Division of Endocrinology, Diabetes and Metabolism at Ohio State University.
In their new investigations, the researchers looked at data from two major heart-health studies, each of which tested patients' blood for 25-hydroxyvitamin D, the biological "precursor" of active vitamin D.
It's a common clinical measure for assessing whether or not an individual has levels of vitamin D needed for good health.
Researchers examined vitamin D levels in the blood collected from more than 3,300 Black participants in the Jackson Heart Study between 2000 and 2004. Over a median of 7.7 years, 584 developed diabetes.
They also examined more than 5,600 participants in the Multi-Ethnic Study of Atherosclerosis (MESA) study, none of whom had diabetes at the study's outset. This group included a range of white, Black, Hispanic and Chinese Americans.
The researchers followed the association of this vitamin D precursor and diabetes for more than nine years.
The MESA study found that as blood levels of vitamin D declined, a person's odds of developing diabetes rose -- and that was "similar across races and ethnicities," Williams said in a university news release.
Obesity might have played role: A further analysis of the MESA data found that higher levels of body fat altered the relationship between vitamin D and diabetes risk.
So does this mean that Black Americans should reach for vitamin D supplements? The jury's out on that, the authors said.
"More research is needed to learn whether vitamin D supplementation among individuals with vitamin D deficiency can improve risk for diabetes," said Dr. Joshua Joseph, a lead researcher on both studies. He's an endocrinologist and an assistant professor in the Division of Endocrinology, Diabetes and Metabolism at Ohio State.
The findings based on the JHS data were published recently in the journal Nutrition and Diabetes. The findings using the MESA data were reported in BMJ Open Diabetes Research and Care.
Both studies were funded by the U.S. National Heart, Lung, and Blood Institute.
The U.S. National Institutes of Health has more on vitamin D.
SOURCE: Ohio State University Wexner Medical Center and College of Medicine, news release, Nov. 10, 2022