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 .
Unchanged renal haemodynamics following high dose ascorbic acid administration in normoalbuminuric IDDM patients.
The object of the study was to test whether high dose ascorbic acid ( AA ) could normalize glomerular hyperfiltration in insulin-dependent diabetes mellitus ( IDDM ) patients . A prospect i ve , double-blind , r and omized , placebo ( tartaric acid , TA ) controlled study design was used , with parallel treatment lasting 4 weeks . Measurements were made before and after treatment , on 24 normoalbuminuric , normotensive male IDDM patients , who were r and omized to ascorbic acid ( n = 12 , age 35 years ( 18 - 39 ) , diabetes duration 12 years ( 2 - 12 ) , BP 128/82 mmHg ( SD 14/6 ) ) , or to placebo ( TA ) ( n = 12 , age 30 years ( 19 - 36 ) , diabetes duration 8 years ( 2 - 17 ) , BP 119/75 mmHg ( SD 9/7 ) . The intervention consisted of 6 enterosoluble tablets of 500 mg AA or 213 mg TA , twice a day , being daily doses of 6 g AA or 2.55 g TA . No significant differences in any of the parameters measured were seen , when comparing results following AA or placebo treatment . The glomerular filtration rate ( GFR , clearance of 125I-iothalamate ) was unchanged while effective renal plasma flow ( ERPF , clearance of 131I-hippuran ) tended to decline in both groups . The GFRs before and after treatment in the AA-treated group were 141 ( SD 15 ) and 134 ( SD 12 ) ml min-1 1.73 m-2 ; NS ( 2p = 0.09 ) . In the TA-treated group they were 142 ( SD 19 ) and 137 ( SD 16 ) ml min-1 1.73 m-2 ; NS ( 2p = 0.20 ) . The ERPFs in the AA group were 584 ( SD 93 ) and 545 ( SD 47 ) ml min-1 1.73 m-2 ; ( 2p = 0.06 ) . In the TA group they were 618 ( SD 108 ) and 574 ( SD 98 ) ml min-1 1.73 m-2 ( 2p = 0.03 ) . The filtration fractions ( FFs ) in the AA group were 0.244 and 0.246 NS . ( ABSTRACT TRUNCATED AT 250 WORDS
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 .