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Trial registered on ANZCTR


Registration number
ACTRN12616000276459
Ethics application status
Approved
Date submitted
29/02/2016
Date registered
2/03/2016
Date last updated
11/06/2019
Date data sharing statement initially provided
11/06/2019
Date results information initially provided
11/06/2019
Type of registration
Prospectively registered

Titles & IDs
Public title
Efficacy of ascorbic acid in improving glycaemic control in type 2 diabetes
Scientific title
Efficacy of ascorbic acid in improving glycaemic control in type 2 diabetes
Secondary ID [1] 288494 0
None
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Type 2 diabetes 297554 0
Condition category
Condition code
Metabolic and Endocrine 297756 297756 0 0
Diabetes

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
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.
Intervention code [1] 293856 0
Treatment: Other
Comparator / control treatment
A placebo intervention will be conducted in a randomized cross-over manner with the ascorbic acid intervention. Similar to the ascorbic acid intervention, a placebo capsule (containing gelatine, calcium carbonate, vegetable magnesium stearate and vegetable cellulose) will be consumed twice daily. The placebo capsules have an identical appearance to the ascorbic acid capsules
Control group
Placebo

Outcomes
Primary outcome [1] 297285 0
Postprandial incremental glucose area under the curve from data obtained through use of a continuous blood glucose monitor
Timepoint [1] 297285 0
For a continuous 48-hour period immediately before and immediately after both 4-month interventions
Secondary outcome [1] 320620 0
HbA1c by whole blood assay
Timepoint [1] 320620 0
Immediately before and immediately after both 4-month interventions
Secondary outcome [2] 320621 0
Time spent in hyperglycaemia and hypoglycaemia (hrs/day) from data obtained through use of a continuous blood glucose monitor
Timepoint [2] 320621 0
For a continuous 48-hour period immediately before and immediately after both 4-month interventions
Secondary outcome [3] 320622 0
Fasting insulin by radioimmunoassay
Timepoint [3] 320622 0
Immediately before and immediately after both 4-month interventions

Eligibility
Key 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.
Minimum age
45 Years
Maximum age
75 Years
Gender
Both males and females
Can healthy volunteers participate?
No
Key exclusion criteria
(i) Having a major medical illness in addition to Type 2 diabetes; (ii) taking >2000 mg metformin per day) or more than 2 different diabetes medications or on insulin therapy; (iii) smokers; (iv) taking vitamin supplements other than those provided by us during the trial

Study design
Purpose of the study
Treatment
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
A third party individual not directly involved in the study will randomly allocate participants into their treatment order using coin toss. Information pertaining to trial allocation of participants will be kept confidential and locked away by the third party. Primary investigators and participants will remain blinded to treatment at all times during the study.
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Coin toss
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s
The people administering the treatment/s
The people assessing the outcomes
The people analysing the results/data
Intervention assignment
Crossover
Other design features
Phase
Phase 2 / Phase 3
Type of endpoint(s)
Efficacy
Statistical methods / analysis

Recruitment
Recruitment status
Completed
Date of first participant enrolment
Anticipated
Actual
Date of last participant enrolment
Anticipated
Actual
Date of last data collection
Anticipated
Actual
Sample size
Target
Accrual to date
Final
Recruitment in Australia
Recruitment state(s)
VIC

Funding & Sponsors
Funding source category [1] 292848 0
Charities/Societies/Foundations
Name [1] 292848 0
Diabetes Australia Research Trust
Address [1] 292848 0
PO Box 3156
Canberra ACT 2601
Country [1] 292848 0
Australia
Primary sponsor type
Individual
Name
Dr Glenn Wadley
Address
Deakin University
School of Exercise and Nutrition Sciences
221 Burwood highway, Burwood
Victoria
3125
Country
Australia
Secondary sponsor category [1] 291593 0
None
Name [1] 291593 0
Address [1] 291593 0
Country [1] 291593 0

Ethics approval
Ethics application status
Approved
Ethics committee name [1] 294349 0
Deakin University Human Research Ethics Committee (EC00213)
Ethics committee address [1] 294349 0
Deakin Research Integrity
Burwood Campus
Postal: 221 Burwood Highway
Burwood Victoria 3125 Australia
Ethics committee country [1] 294349 0
Australia
Date submitted for ethics approval [1] 294349 0
23/11/2015
Approval date [1] 294349 0
05/01/2016
Ethics approval number [1] 294349 0
2015-319

Summary
Brief summary
A key defect in type 2 diabetes (T2D) is the impaired ability to respond to insulin and remove circulating glucose and store it in muscle. We have recently established that long-term and high dose vitamin C supplementation improves insulin sensitivity in muscle in people with T2D to a degree which is clinically significant. Therefore, this cheap and safe supplement is likely to be an effective adjunct therapy to complement current standard care and control excess blood glucose levels.
Therefore, the aim of this project is to investigate whether antioxidant vitamin C supplementation results in a clinically significant improvement in glycaemic control in people with T2D.
Forty males and females with T2D (aged 45-75 yrs) will be recruited and undergo placebo and vitamin C (0.5g twice daily) in a double-blind, randomized, cross-over manner. Outcome measures will be conducted at the beginning (baseline) and end of each 4 month treatment and involve a visit at each of these times to the Clinical Research Laboratory at Deakin University. There will be a 4 week washout between treatments,
so total involvement will be 9 months.
Participants will be asked to complete a 4-day food and physical activity diary the week prior to each laboratory visit. Participants will have their height, weight and blood pressure measured and a DXA scan to measure body composition. Participants will be fitted with an accelerometer to measure physical activity and a Continuous Glucose Monitoring (CGM) system to monitor interstitial blood glucose. The following morning they will visit the laboratory in a fasted state and have a blood sample taken and eat a healthy breakfast
provided by us. The accelerometer and CGM will be worn at home by participants, and (blinded) measurements will occur over a continuous 48-hour period while participants eat pre-prepared healthy meals provided by us.
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 63370 0
Dr Glenn Wadley
Address 63370 0
Centre for Physical Activity and Nutrition Research
School of Exercise and Nutrition Sciences, Faculty of Health
Deakin University
221 Burwood Hwy
Burwood VIC 3125
Australia
Country 63370 0
Australia
Phone 63370 0
+61 3 92446018
Fax 63370 0
+61 3 92446017
Email 63370 0
glenn.wadley@deakin.edu.au
Contact person for public queries
Name 63371 0
Dr Glenn Wadley
Address 63371 0
Centre for Physical Activity and Nutrition Research
School of Exercise and Nutrition Sciences, Faculty of Health
Deakin University
221 Burwood Hwy
Burwood VIC 3125
Australia
Country 63371 0
Australia
Phone 63371 0
+61 3 92446018
Fax 63371 0
+61 3 92446017
Email 63371 0
glenn.wadley@deakin.edu.au
Contact person for scientific queries
Name 63372 0
Dr Shaun Mason
Address 63372 0
School of Exercise and Nutrition Sciences, Faculty of Health
Deakin University
221 Burwood Hwy
Burwood VIC 3125
Australia
Country 63372 0
Australia
Phone 63372 0
+61 3 9244 6577
Fax 63372 0
+61 3 9244 6017
Email 63372 0
s.mason@deakin.edu.au

Data sharing statement
Will individual participant data (IPD) for this trial be available (including data dictionaries)?
No
No/undecided IPD sharing reason/comment
This new question was not present in the registry at the time of registration, and our trial did not originally intend to have IPD sharing
What supporting documents are/will be available?
No other documents available
Summary results
Have study results been published in a peer-reviewed journal?
Yes
Journal publication details
Publication date and citation/details [1] 2300 0
Mason SA, Rasmussen B, van Loon LJC, Salmon J & Wadley GD. Ascorbic acid supplementation improves postprandial glycaemic control and blood pressure in individuals with type 2 diabetes: Findings of a randomized cross-over trial. Diabets Obes Metab. 2019; 21(3): 674-682. doi: 10.1111/dom.13571. Epub 2018 Dec 2
Other publications
Have study results been made publicly available in another format?
No
Results – plain English summary
The main aim of this study was to investigate whether ascorbic acid (AA) supplementation improves glycaemic control under free-living conditions in individuals with type 2 diabetes. We also investigated effects of AA supplementation on blood pressure. Thirty-one individuals with type 2 diabetes (26 males and 5 females; average age 62 years; average duration of diabetes 5.6 years) and moderate glucose control (average HbA1c 7.6%) were enrolled in a randomized cross-over study involving 4 months of supplementation with oral AA (2 × 500 mg/day) or placebo. Participants took both AA and placebo, however the order of each 4-month period was randomized and blinded to both participants and researchers.
AA supplementation significantly decreased the average daily post-meal glucose response, the duration of day spent in hyperglycaemia, the average 24-hour glucose concentration, blood pressure, and a marker of oxidative stress in blood as compared to placebo.
Overall, individuals with type 2 diabetes experienced improved post-meal and 24-hour glucose levels and decreased blood pressure after 4 months of AA supplementation as compared to placebo. These findings offer evidence for the proposed use of AA as an adjunct therapy to improve glycaemic and blood pressure control in individuals with type 2 diabetes.