The aim of the study was to investigate whether ascorbic acid (AA) supplementation improves postprandial glucose responses under free living conditions in people with type 2 diabetes (T2D). Thirty-one people with T2D (26 male, 5 female; aged 61.8 ± 6.8y; duration of diabetes 5.6 ± 4.6y [mean ± SD]) and stable glucose control (HbA1c 7.6 ± 0.7%) and blood pressure (SBP 139 ± 10; DBP 85 ± 9 mmHg) completed a randomized cross-over study involving 4 months of oral AA (2 x 500 mg/day) supplementation and 4 months of placebo supplementation (# ACTRN12616000276459). A minimum wash-out of 4 weeks separated treatments. Participants were affixed with continuous glucose monitors for 48h and consumed standardized meals pre and post supplementation. Intention to treat analyses were used to analyse data. Postprandial glucose area under the curve for 3.5h post meals (10.5h total) and the percent of day spent in hyperglycaemia (>10 mmol/l) were significantly lower by 31% and 11% (∼2.5h) after AA supplementation when compared to placebo, respectively (p<0.05). Significantly lower systolic (-6 mmHg) and diastolic (-4 mmHg) blood pressures were also found after AA supplementation compared to placebo. There were no effects of AA supplementation on percent of day spent in hypoglycaemia (<4 mmol/l), average 24h glucose or HbA1c. Treatments were well tolerated by participants, with no adverse effects reported. Capsule compliance was high for both treatments (AA: 93 ± 11%; placebo: 95 ± 7%).

In summary, AA supplementation attenuated the daily post-prandial glucose response and the proportion of day spent in hyperglycaemia in people with T2D. AA also improved blood pressure in this group. This evidence collected under free-living conditions strengthens the argument for AA as a beneficial adjunct therapy to improve glycaemic control and cardio-metabolic health for people with T2D.


S. Mason: None. B. Rasmussen: None. G.D. Wadley: None.

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