Vitamin D Levels in Subjects With and Without Type 1 Diabetes Residing in a Solar Rich Environment

OBJECTIVE

Previous studies, largely in northern Europe, have suggested an association between type 1 diabetes and reduced serum 25-hydroxy(OH) vitamin D levels, a concept we tested in individuals residing in a solar-rich region (Florida).

RESEARCH DESIGN AND METHODS

Serum samples from 415 individuals residing in Florida were cross-sectionally analyzed: 153 control subjects, 46 new-onset type 1 diabetic patients, 110 established type 1 diabetic patients (samples ≥5 months from diagnosis), and 106 first-degree relatives of the diabetic patients.

RESULTS

In this study, 25-OH vitamin D levels (median, range, interquartile range [IQR]) were similar among control subjects (20.1, below detection [bd]–163.5, 13.0–37.4 ng/ml), new-onset type 1 diabetic patients (21.2, bd–48.6, 12.2–30.2 ng/ml), established type 1 diabetic patients (23.2, bd–263.8, 13.8–33.9 ng/ml), and first-degree relatives (22.2, bd–59.9, 12.7–33.1 ng/ml) (P = 0.87). Mean 25-OH vitamin D levels were less than the optimal World Health Organization level of 30 ng/ml in all study groups.

CONCLUSIONS

Reduced serum 25-OH vitamin D levels were not specifically associated with type 1 diabetes. The uniform suboptimal 225-OH vitamin D levels, despite residence in a zone with abundant sunshine, support additional dietary vitamin D fortification practices.The role for environment in the development of type 1 diabetes has remained elusive, with multiple factors purported to modulate risk for this disease (e.g., viruses, breast-feeding, age for cereal introduction, and childhood immunizations) (1,2). Further to this list is vitamin D levels (3), with previous studies suggesting type 1 diabetic patients had lower serum concentrations of this metabolite than healthy control subjects (4–6) as well as disease-associated polymorphisms in a vitamin D metabolism gene (7). Although certainly intriguing, we note the aforementioned studies were largely undertaken in northern European countries (4,5), whereas the one study performed in the U.S. failed to provide values among healthy control subjects and, hence, did not identify disease specificity (6). Therefore, we measured serum 25-hydroxy (OH) vitamin D levels from type 1 diabetic patients, their first-degree relatives, and healthy control subjects all residing in a solar-rich region (Florida).