 Patients will be randomised by a dynamic randomisation method called minimization which allocates patients to treatment group by checking the allocation of similar patients already randomised, and allocating the next treatment group live to best balance the treatment groups across all stratification variables. The minimization will be carried out by the NHMRC clinical trials centre in Sydney , and the patient will be randomized to either placebo or vitamin. Each patient will collect their tablets from the clinical trials pharmacy. The Clinical Trials Pharmacy will dispense either vitamin or placebo. All study personnel and participants will be blinded to treatment assignment for the duration of the study. To enhance the quality of measurement and increase the power of the study by avoiding dilution of effect adherence to medication will be measured electronically with electronic pill caps Medication Event Monitoring System VI, ARRDEX Ltd. This will allow us to assess actual pharmacological exposure in an objective manner. 