Effect of Combined Vitamin D Administration Plus Dietary Intervention on Oxidative Stress Markers in Patients with Metabolic Syndrome: A pilot Randomized Study

Background: Metabolic syndrome (MetS) patients can have low 25-hydroxyvitamin D 25(OH)VitD levels, which may be associated with increased oxidative stress. There is little data on the effect of 25(OH)VitD administration plus dietary intervention on oxidative stress markers in these patients.

Aim: To study the effect of 25(OH)VitD administration plus dietary intervention on oxidative stress markers in MetS patients.

Methods: This is a pre-specified analysis of a previously published study (NCT01237769 ClinicalTrials.gov). MetS participants (n = 50, 52 ± 10 years) were given dietary instructions and were randomized to 25(OH)VitD 2.000 IU/day p.o. (Suppl group) or no supplementation (No-Suppl group). Serum 25(OH)VitD, oxidized LDL (ox-LDL), paraoxonase activity (PON-1), arylesterase activity (ARYL) and urine 8-isoprostane (8-iso-PGF) levels were measured at baseline and after 3 months.

Results: MetS patients had low baseline 25(OH)VitD levels, which increased by 90% in the Suppl group [from 16.1 (3.3-35.1) to 30.6 (8.4-67.6) ng/mL, p = 0.001] and by 33.3% in the No-Suppl group [from 9.9 (4.0-39.6) to 13.2 (3.5-36.8) ng/mL, p = NS] after intervention. Ox-LDL, PON-1 and ARYL did not change significantly at follow-up in both groups, except for urine 8-iso-PGF levels that decreased by 22.7% in the Suppl group [from 48.8 (26.8-137.1) to 37.7 (12.3-99.0) ng/mmol creatinine, p = 0.015] and by 14.4% in No-Suppl group [from 45.8 (16.6-99.3) to 39.2 (13.3-120.1) ng/mmol creatinine, p = NS]. The reduction in 8-iso-PGF levels did not differ significantly between the 2 groups.

Conclusion: The administration of 25(OH)VitD plus dietary intervention in patients with MetS was not associated with meaningful reductions in oxidative stress markers compared with dietary intervention alone.