Plain English Summary
Background and study aims
Small studies have shown that vitamin D, a hormone that the skin usually makes using sunshine, may be able to reduce blood pressure and improve blood vessel health in people with type 2 diabetes. It is not clear what the best dose of vitamin D to use is, or how long the effect of a single large dose lasts for.
The aim of the study is therefore to compare the effect of two different doses of vitamin D with placebo (dummy) and measure whether an effect on blood vessel health and blood pressure can be seen at 8 and 16 weeks after the dose.
Who can participate?
Adults aged 18 years and older with type 2 diabetes
What does the study involve?
The study lasts for 16 weeks. At the start, participants are randomly allocated to one of three groups. They receive two teaspoons of oil, which will contain either 100,000 units vitamin D3, 200,000 units vitamin D3, or a matching placebo (dummy).
Participants are assessed at the start, and 8 weeks and 16 weeks. Each visit lasts 1.5 hours.
At each visit, participants receive some or all of the following depending on which visit it is:
-Blood pressure measurement
-Blood sample taken
-Test the function of the artery in their arm. The artery is scanned with an ultrasound machine before and after inflating a blood pressure cuff on their forearm for 5 minutes. The test is repeated after the participant is given a medication (GTN) spray under their tongue
-Wear a blood pressure cuff and a heart rate monitor (ECG) for 24 hours including at home.
What are the possible benefits and risks of participating?
Although participants are unlikely to benefit directly by taking part in the trial, those who receive the vitamin D might find that blood pressure is lowered.
Although this dose of vitamin D has been used before and is known to be safe there is a small possibility of side effects. Participants are closely monitored for side effects caused by high calcium levels: sickness, diarrhoea, thirst or dizziness. To reduce the chance of vitamin D increasing the calcium level in their blood, participants are also asked not to take vitamin D supplements or calcium supplements whilst taking part in this study.
Having blood taken can cause some bruising. The blood pressure cuff causes mild discomfort to some people.
Where is the study run from?
Ninewells Hospital Dundee (UK)
When is the study starting and how long is it expected to run for?
October 2006 to January 2010
Who is funding the study?
Diabetes UK (UK)
Who is the main contact?
Dr Miles Witham (Scientific)
Dr Miles Witham
Section of Ageing and Health
+44 (0)1382 632436
The effect of different doses of vitamin D(3) on markers of vascular health in patients with type 2 diabetes: a randomised controlled trial
To compare the effect of two different doses of vitamin D3 on vascular function in patients with type two diabetes.
Tayside Local Research Ethics Committee,10/09/2007, ref: 07/S1401/101
Double blind randomised controlled trial
Primary study design
Secondary study design
Randomised controlled trial
Patient information sheet
Type two diabetes mellitus
Single dose of placebo, 100,000 units or 200,000 units of vitamin D3. Each patient will be followed-up for 16 weeks.
Primary outcome measure
Change in endothelial function measured using flow-mediated dilation of the brachial artery (added 26/02/2018: at baseline, 8 and 16 weeks after vitamin D3 treatment).
Secondary outcome measures
Current secondary outcomes (as of 26/02/2018):
All measures are recorded at baseline, 8 and 16 weeks after vitamin D3 treatment.
1. Office blood pressure is measured using an oscillometric system
2. Brain Natriuretic Peptide is measured from a blood sample
3. Insulin sensitivity measured using Homeostasis Model Assessment (HOMA)
4. Parathyroid Hormone (PTH) is measured from a blood sample
5. Vitamin D levels are measured using the 25 hydroxy vitamin D test
6. Calcium levels are measured from a blood sample
Previous secondary outcomes:
1. Office and 24-hour Blood Pressure (BP)
2. Brain Natriuretic Peptide (BNP)
3. Heart rate variability
4. Insulin sensitivity (Homeostasis Model Assessment [HOMA])
5. Angiotensin II, renin, aldosterone
6. Parathyroid Hormone (PTH) and 25 hydroxy vitamin D levels
Overall trial start date
Overall trial end date
Reason abandoned (if study stopped)
Participant inclusion criteria
Diagnosis of type two diabetes mellitus.
Target number of participants
Participant exclusion criteria
1. Taking vitamin D supplements
2. Serum 25 hydroxy vitamin D level of greater than 100 nmol/L
3. Serum creatinine greater than 200 umol/l
4. Liver function tests greater than three times the upper limit of normal
5. Hyper- or hypo-calcaemia (corrected calcium greater than 2.55 or less than 2.15 mmol/l, respectively)
6. Metastatic malignancy
7. Inability to give informed consent
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
Section of Ageing and Health
Diabetes UK (UK) (grant ref: BDA: RD06/0003429)
Funding Body Type
private sector organisation
Funding Body Subtype
Results and Publications
Publication and dissemination plan
IPD sharing statement: The protocol is available from the authors on request but is not available online. Study data are available for non-commercial, bona-fide academic analyses in collaboration with the authors; decisions on data access will be made between the investigators and the Sponsor (University of Dundee). Participant consent for unrestricted sharing of individual participant data was not obtained
Contact for data sharing: Dr Catrina Forde (email@example.com)
Intention to publish date
Participant level data
Available on request
Basic results (scientific)
1. 2010 results in http://www.ncbi.nlm.nih.gov/pubmed/20596692
Witham MD, Dove FJ, Dryburgh M, Sugden JA, Morris AD, Struthers AD, The effect of different doses of vitamin D(3) on markers of vascular health in patients with type 2 diabetes: a randomised controlled trial., Diabetologia, 2010, 53, 10, 2112-2119, doi: 10.1007/s00125-010-1838-1.
- ISRCTN50587697_BasicResults_21Feb18.pdf Uploaded 26/02/2018