Summary of the major cross-sectional and longitudinal studies evaluating the relationship between vitamin D and pre-diabetes
| Author | Study | Type of population | Number and type of subjects | Remarks |
| Kwon and Lim34 | Cross-sectional | South Korean | 60 subjects with pre-diabetes, aged 20–65 years | Subjects with pre-diabetes were more likely to have low serum 25(OH)D levels. |
| Karras et al35 | Case–control | Greek | 144 individuals with pre-diabetes and 81 healthy age-matched control subjects, aged >65 years | Vitamin D deficiency with high parathyroid hormone levels was significantly associated with glycemic dysregulation in patients with pre-diabetes. |
| Zagami et al36 | Cross-sectional | Italians | 286 subjects including those with pre-diabetes (n, 83) | Subjects with pre-diabetes had significantly reduced 25(OH)D levels. |
| Ekbom and Marcus37 | Cross-sectional | Swedish | 202 obese children, aged 4.5–17.9 years | Low serum 25(OH)D levels were strongly associated with higher risk of impaired fasting glucose. |
| Abbasi et al25 | Cross-sectional | NorthAmericans | 488 non-diabetic subjects including individuals with pre-diabetes | Subjects with pre-diabetes and low circulating 25(OH)D concentrations were the most insulin resistant and had impaired β cell function. |
| Deleskog et al27 | Longitudinal case–control study | Swedish | Normal glucose tolerance at baseline and progressed to either pre-diabetes (304 women, 428 men) or type 2 diabetes (47 women, 87 men) | High serum 25(OH)D concentrations predicted a reduced risk of T2DM in individuals with pre-diabetes, but not in those with normal glucose tolerance. |
| Gupta et al26 | National Health and Nutrition Examination Survey, 2001–2006 | NorthAmerican Caucasians | Pre-diabetic and prehypertensive subjects (men, n, 898 and women, n, 813) | Individuals with low 25(OH)D levels had elevated the risk for pre-diabetes. |
| Dutta et al14 | Cross-sectional | Asian Indians residing in India (West) | 157 individuals with pre-diabetes | Vitamin D deficiency/insufficiency was associated with worsened insulin resistance in individuals with pre-diabetes. |
| Banerjee et al15 | Cross-sectional | Asian Indians residing in India (West) | 73 individuals with pre-diabetes, 77 individuals with T2DM and 52 healthy control subjects. | Serum 25(OH)D in subjects with pre-diabetes and T2DM was found to be inversely correlated with the serum levels of insulin. |
T2DM, type 2 diabetes mellitus.