Vitamin D Replacement in Insulin Resistant South Asians (VITALITY)

Inclusion Criteria:

We will include the following people if they meet all criteria:

1. 25-75 year old south Asian (Bangladeshi, Indian or Pakistani) men or women.
2. A low vitamin D level (defined by a specific marker, 25(OH)VitD <25 nmol/L)
3. Insulin resistance, defined as homeostatic model assessment of Insulin resistance (HOMA1-IR) ≥ 1.93.

Exclusion Criteria:

We will exclude people if they have any one of the following:

1. Those who have been told by a doctor they have diabetes (Type 1 or 2).
2. Those who developed new diabetes (World Health Organisation (WHO) 1999 guidelines) detected on the Screening Visit fasting glucose test (such participants will be offered a confirmatory test to determine if they have diabetes with an oral glucose tolerance test) or the oral glucose tolerance test at Baseline Visit. Any individual with new diabetes will have follow up arranged with a doctor. If the confirmatory test does not show new diabetes, the participant will is eligible to re-enter the study.
3. HbA1c ≥ 7.0% which is suggestive of diabetes.
4. Pre-existing calcium and/or Vitamin D tablets (D2 ergocalciferol or D3 cholecalciferol) / therapy (e.g. intramuscular injections, oral liquid preparations) or previous adverse reaction to Vitamin D (D2 or D3). Any individual who has previously been on these therapy must have been off Vitamin D/ Calcium for at least six months.
5. Pregnancy or breast feeding females, or actively trying/ intending to become pregnant during the planned six month trial.
6. A history of known or newly detected hypercalcaemia or hypocalcaemia, hyperparathyroidism (that induce high calcium levels), kidney stones or other kidney problems/ low kidney function (estimated glomerular filtration rate <60 = Chronic kidney disease stage 3, 4 or 5) or known history of liver problems/ disorders.
7. A history of known bone diseases (e.g. osteoporosis, osteomalacia, osteopetrosis) or muscle diseases.
8. Any participant discovered to have new kidney/ liver/ bone or other health problems discovered during Screening or Baseline visit. Such individuals will have appropriate follow up organised. A raised Parathyroid Hormone (PTH) will be considered in the clinical context of symptoms, Alkaline Phosphatase (ALP) and Vitamin D level (i.e. may or may not be excluded).
9. Terminal illness, malignancy or physical inability to give consent (not language barriers).
10. Taking medications which may interfere with Vitamin D metabolism (phenytoin, carbamazepine, primidone and barbiturates) or potentially leading to other problems (bendroflumethiazide, digoxin).
11. Participants unable to commit time for the six month study (e.g. holiday abroad, work commitments).
12. Actively taking part in another interventional study (e.g. medication, lifestyle Randomised controlled trials); observational and cross sectional studies are still permitted.