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 .
Antioxidant supplementation decreases lipid peroxidation biomarker F(2)-isoprostanes in plasma of smokers.
Free radicals in cigarette smoke ( CS ) cause oxidative damage to proteins , DNA , and lipids , contributing to the pathobiology of atherosclerosis , heart disease , and cancer . In vitro studies have shown that antioxidants quench free radicals and ameliorate certain aspects of biomolecular damage caused by CS . It is hypothesized that a combination of antioxidants is more effective than a single antioxidant , due to their interactions . To investigate whether supplemental antioxidants reduce CS-related lipid peroxidation in vivo and whether they are more effective in combination , we conducted an intervention study in smokers . In a r and omized double-blind placebo-controlled trial , we investigated whether vitamin C or an antioxidant mixture containing vitamin C , alpha-lipoic acid , and vitamin E decreases plasma F(2)-isoprostane levels , an index of oxidant stress , in smokers . Plasma of 126 smokers ( mean age , 46 years ; age range , 20 - 78 years ) was analyzed for F(2)-isoprostanes at baseline and after intervention with antioxidants and placebo . In smokers with a body mass index ( BMI ) above the median , 2 months of daily supplementation with 500 mg of vitamin C decreased plasma F(2)-isoprostane levels by 28.8 pmol/liter when compared with the placebo group ( P = 0.001 ) ; levels in the mixture group were 7.45 pmol/liter lower after treatment , but this difference was not statistically significant ( P = 0.14 ) . There was no treatment effect in smokers with a low BMI .  BMI was significantly positively associated with plasma F(2)-isoprostane levels ( trend P = 0.001 ) . Antioxidants decrease smoking-related lipid peroxidation markers of oxidative stress in humans with high BMI . Our results do not indicate that an antioxidant combination is more effective than vitamin C alone . The intake of antioxidants may help prevent smoking-related diseases . Smoking cessation should still be considered the most effective way to prevent smoking-related diseases
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 .