Effects of vitamin D supplementation on insulin resistance and dyslipidemia in overweight and obese premenopausal women.

Introduction: Vitamin D deficiency is a common problem, and it is related to increased risk of obesity, metabolic syndrome, atherosclerosis, and cardiovascular disease. Vitamin D has a beneficial effect on dyslipidemia and insulin secretion. We aimed to investigate the impact of vitamin D supplementation on anthropometric and laboratory parameters in overweight and obese premenopausal women.

Material And Methods: Seventy-two overweight and 50 obese vitamin-D-deficient premenopausal women (mean age: 43.1 ±10.4 years) were included in the study. Baseline mean 25-hydroxyvitamin D [25(OH)D] level was 6.1 (min.-max. = 2.9-15.8) ng/ml in overweight and was 5.6 (min.-max. = 3.0-22.0) ng/ml in obese subjects. At baseline and at the sixth month of supplementation, serum 25(OH)D, intact parathormone (iPTH), calcium, phosphorus, homeostasis model assessment of insulin resistance (HOMA-IR), and lipid profiles were assessed.

Results: Following vitamin D supplementation in overweight and obese subjects, serum 25(OH)D increased from 6.1 to 34.7 ng/ml and 5.6 to 34.7 ng/ml, respectively ( < 0.001). At the sixth month of supplementation in both overweight and obese subjects, a significant reduction was detected in HOMA-IR ( < 0.001), low-density lipoprotein cholesterol (LDL-C) ( = 0.046, = 0.044; respectively) and iPTH levels ( ≤ 0.001, < 0.001; respectively). A negative adjusted correlation was found between changes in 25(OH)D and HOMA-IR ( = -0.581, < 0.001; = -0.389, = 0.005; respectively). A 1 ng/ml increase in serum 25(OH)D level led to a 0.30-fold reduction in HOMA-IR level ( = 0.002).

Conclusions: Our results support the effect of vitamin D supplementation in HOMA-IR and LDL-C improvement in both obese and overweight subjects. Further studies focused on low serum 25(OH)D levels with insulin resistance and dyslipidemia are needed.