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 .
Plasma vitamin C level, fruit and vegetable consumption, and the risk of new-onset type 2 diabetes mellitus: the European prospective investigation of cancer--Norfolk prospective study.
BACKGROUND Epidemiologic studies suggest that greater consumption of fruit and vegetables may decrease the risk of diabetes mellitus , but the evidence is limited and inconclusive . Plasma vitamin C level is a good biomarker of fruit and vegetable intake , but , to our knowledge , no prospect i ve studies have examined its association with diabetes risk . This study aims to examine whether fruit and vegetable intake and plasma vitamin C level are associated with the risk of incident type 2 diabetes . METHODS We administered a semiquantitative food frequency question naire to men and women from a population -based prospect i ve cohort ( European Prospect i ve Investigation of Cancer-Norfolk ) study who were aged 40 to 75 years at baseline ( 1993 - 1997 ) when plasma vitamin C level was determined and habitual intake of fruit and vegetables was assessed . During 12 years of follow-up between February 1993 and the end of December 2005 , 735 clinical ly incident cases of diabetes were identified among 21 831 healthy individuals . We report the odds ratios of diabetes associated with sex-specific quintiles of fruit and vegetable intake and of plasma vitamin C levels . RESULTS A strong inverse association was found between plasma vitamin C level and diabetes risk . The odds ratio of diabetes in the top quintile of plasma vitamin C was 0.38 ( 95 % confidence interval , 0.28 - 0.52 ) in a model adjusted for demographic , lifestyle , and anthropometric variables . In a similarly adjusted model , the odds ratio of diabetes in the top quintile of fruit and vegetable consumption was 0.78 ( 95 % confidence interval , 0.60 - 1.00 ) . CONCLUSIONS Higher plasma vitamin C level and , to a lesser degree , fruit and vegetable intake were associated with a substantially decreased risk of diabetes . Our findings highlight a potentially important public health message on the benefits of a diet rich in fruit and vegetables for the prevention of diabetes
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 .