Overall , vitamin C did not modify glucose , HbA1c and insulin concentrations .
Meta-regression analyses showed that age was a modifier of the effect of vitamin C on insulin concentration .
Furthermore , the effect size was associated with baseline BMI and plasma glucose levels , and with the duration of the intervention .
In conclusion , greater reduction in glucose concentrations observed in patients with diabetes , older individuals and with more prolonged supplementation .
R and omised controlled trials ( RCTs ) have observed contrasting results on the effects of vitamin C on circulating biomarkers of glycaemic and insulin regulation .
Does short-term vitamin C reduce cardiovascular risk in type 2 diabetes?
OBJECTIVE Vitamin C is a powerful antioxidant that is potentially useful in the prevention of atherosclerosis in diabetic individuals . However , the mechanism(s ) of vitamin C 's anti-atherosclerotic effects in vivo are unresolved , and clinical trials in nondiabetic individuals have yielded conflicting results . Therefore , we performed 32 studies in a r and omized , crossover , dose-response trial in 8 volunteers with type 2 diabetes to determine the effects of vitamin C on serum vitamin C levels , lipids , inflammation , and coagulation . METHODS Well-controlled , type 2 volunteers received , in r and omized order for 2-week periods , each of the following : 1 ) no supplemental vitamin C , 2 ) low-dose vitamin C ( 250 mg/day ) , 3 ) medium-dose vitamin C ( 500 mg/day ) , and 4 ) high-dose vitamin C ( 1,000 mg/day ) . A high-caloric content lunch was ingested during each study arm to enhance oxidative stress . Serum vitamin C levels and atherosclerotic risk factors including lipids and markers of oxidative stress , inflammation , and hypercoagulation were determined . RESULTS Serum vitamin C levels increased significantly at all dosages . In addition , the high-caloric content meal result ed in acute elevations of glucose , insulin , and triglycerides for several hours postmeal . However , no significant effect of vitamin C was observed on lipid parameters or any of the surrogate markers of oxidative stress , inflammation , or hypercoagulability . CONCLUSION Our study suggests that if vitamin C does have anti-atherosclerotic effects in diabetes , it does not exert them through the traditional pathways identifiable by established surrogate markers of cardiovascular risk
Overall , vitamin C did not modify glucose , HbA1c and insulin concentrations .
Meta-regression analyses showed that age was a modifier of the effect of vitamin C on insulin concentration .
Furthermore , the effect size was associated with baseline BMI and plasma glucose levels , and with the duration of the intervention .
In conclusion , greater reduction in glucose concentrations observed in patients with diabetes , older individuals and with more prolonged supplementation .
R and omised controlled trials ( RCTs ) have observed contrasting results on the effects of vitamin C on circulating biomarkers of glycaemic and insulin regulation .