The D-Health trial aims to determine whether supplementing older Australian adults with vitamin D can change health outcomes such as cancer and cardiovascular disease. It is the second-largest trial of high-dose supplementation ever conducted and will provide useful information to inform policy decisions about population-wide supplementation (for example, with food fortification).
The trial has been funded by the NHMRC from 2013 to 2021. Between January 2014 and May 2015 we enrolled 21,315 men and women aged over 60 years from across Australia. Most were randomly selected using the electoral roll as the sampling frame, with a small number of volunteers also joining the study.
We randomised participants to 60,000 IU of vitamin D or placebo, taken orally once per month for 5 years. We measure outcomes using multiple different methods:
- Each year we ask participants to complete an annual survey in which we ask them about newly diagnosed health conditions. We also ask them to complete scales which measure outcomes such as mood, quality of life, and pain.
- Through linkage with Medicare and Pharmaceutical Benefits Scheme databases we can capture outcomes (often using medication as a surrogate) such as diabetes, high blood pressure, high cholesterol, infection, osteoporosis, and skin cancer.
- Through linkage with admitted patient datasets we can capture outcomes such as heart attack, stroke, and fracture.
- We are obtaining cancer and mortality outcomes through linkage with state-based cancer and death registers.
- We are conducting a number of sub-studies in which randomly selected participants are asked to complete additional diaries (falls, respiratory infection), telephone surveys (cognition) or donate blood samples (telomere length, cholesterol).
The trial is due to finish in June 2020, with final follow-up in 2021 and ongoing analyses.
The rationale and methods of the trial have been published. https://www.ncbi.nlm.nih.gov/pubmed/27086041.
To find out more about the D-Health trial, please visit the participant and information website.