Efficacy of ascorbic acid in improving glycaemic control in type 2 diabetes

INTERVENTION: People with type 2 diabetes will undergo supplementation with oral capsules of ascorbic acid (0.5g twice daily) and placebo for four months each in a double‐blind, randomized, cross‐over manner. A four‐week wash‐out period will separate the different interventions. At the start and end of each four‐month intervention, participants will undergo a number of measurements. These measurements include whole‐body dual‐energy X‐ray absorptiometry (DXA) to measure body composition, and a fasting blood sample to measure plasma ascorbic acid, glucose, insulin, lipids and HbA1c. At the start and end of each four‐month intervention, participants will also be fitted with a continuous glucose monitor (CGM) for measurement of postprandial glucose and an accelerometer to objectively measure physical activity. CGMs and accelerometers will be worn and provide measurements over a continuous 48h‐period at each time point. A diet of pre‐packaged and fresh nutrient‐controlled foods will be provided to participants for these 48h. For the four days prior each laboratory visit, participants will complete a 4‐day food diary and physical activity survey to monitor consistency of nutrient intake and physical activity during the study duration. Capsule compliance during the study duration will be encouraged through regular weekly phone calls and/or SMS contact. In addition, actual capsule compliance will be measured at the end of treatments by determining the percentage of capsules consumed relative to the expected number that should be consumed during the treatment period. CONDITION: Type 2 diabetes PRIMARY OUTCOME: Postprandial incremental glucose area under the curve from data obtained through use of a continuous blood glucose monitor SECONDARY OUTCOME: Fasting insulin by radioimmunoassay HbA1c by whole blood assay Time spent in hyperglycaemia and hypoglycaemia (hrs/day) from data obtained through use of a continuous blood glucose monitor INCLUSION CRITERIA: (i) Type 2 diabetes with glycaemic control that is modest (HbA1c between 7.0% and 9.0%); (ii) aged 45‐75 years; (iii) body mass index < 35 kg/m2; (iv) blood pressure <160/90 mmHg.