There may be an independent association between higher plasma 25(OH)D concentrations of ≥50 mg/mL or 125 nmol/L and a lower risk (80%) for diabetes, according to a study published in PLoS One.
Researchers conducted a population-based cohort study of 903 older, middle-income, community-dwelling Caucasian adults living in southern California identified as free of prediabetes or diabetes.
They had a documented visit to a NIH Lipid Research Clinic from 1997 to 1999, during which they served as an untreated comparison group. The purpose of the study was to determine, in a prospective cohort study with a 12-year follow-up, whether lower levels of plasma 25(OH)D or 1,25(OH)2D were associated with a higher incidence of diabetes and prediabetes.
Of the 903 participants, a total of 47 and 337 individuals were diagnosed with diabetes and prediabetes during the study period, respectively.
Study results found that levels of plasma high-density lipoprotein-cholesterol were lower in individuals who later were diagnosed with diabetes or prediabetes, and the lower use of vitamin D and calcium supplements at baseline was also associated with the development of diabetes compared with those who did not develop diabetes. The study found the baseline use of calcium supplements was associated with a lower risk of developing diabetes, and a borderline trend of lower incident diabetes in individuals who took vitamin D at baseline (P <.05 and P =.06, respectively).
Plasma 25(OH)D concentrations >30 ng/mL or 75 nmol/L were associated with a 70% lower incidence of diabetes, with hazard ratios (HRs) of 0.31 and 0.29 for concentrations of 30 to 39 ng/mL and 40 to 49 ng/mL, respectively. There was an 81% lower incidence rate of diabetes in individuals with the highest levels of 25(OH)D (HR 0.19). Associations between prediabetes and 25(OH)D were weak compared with the association with diabetes.
Researchers found that for each 10 ng/mL increase in serum 25(OH)D, individuals who took calcium at baseline had a HR of 0.55 (95% CI, 0.31-0.99), whereas those who took no calcium at baseline had a HR of 0.69 (95% CI, 0.49-0.98). After stratifying for PTH level, regular strenuous exercise, and metabolic syndrome, there were still persistently high risks for diabetes with low serum 25(OH)D.
The researchers concluded that there is a significantly inverse relationship association between the risk for diabetes and the serum 25(OH)D levels, and suggest the target plasma level be no less than 40 ng/mL or 100 nmol/L. The 80% lower incidence risk for diabetes with levels ≥50 is above the expert consensus panel recommended serum level and should be approached with caution by clinicians. There was no association observed between 1,25(OH)2D level and risk for diabetes.
Park SK, Garland CF, Gorham ED, BuDoff L, Barrett-Connor E. Plasma 25 hydroxyvitamin D concentration and risk of type 2 diabetes and pre-diabetes: 12-year cohort study. PLoS One. 2018;13(4):e0193070.