Extrait

Background and study aims Vitamin D helps the body to absorb calcium and phosphorus from the diet and is important for keeping bones healthy. Low vitamin D levels are common in older people in the UK, especially during winter months. Moderate vitamin D deficiency may play a role in causing osteoporosis and fractures and has also been associated with an increased risk of cardiovascular disease, cancer and death. However, it is unclear whether supplementation with vitamin D has any beneficial effects on any of these diseases. Many people in Britain do not get enough sun exposure to maintain what are believed to be healthy vitamin D levels. Only small amounts of vitamin D are derived from food, chiefly from liver and oily fish. There is substantial uncertainty about the optimal dose of vitamin D to use in large trials testing effects on bone health and other disease outcomes. It is possible that the doses of vitamin D used in previous trials to prevent fractures may have been too low to maintain healthy bones and to demonstrate other health benefits in older people. The aim of the present study is to determine the optimal daily dose of vitamin D required to maintain blood levels of vitamin D in older people. It will assess the biochemical effects on blood levels of 25-hydroxy-vitamin D (25[OH]D) and parathyroid hormone of different amounts of vitamin D3 daily or a dummy tablet (placebo) when administered for one year. Who can participate? About 300 men and women aged 65 or older. What does the study involve? Participants will be randomly allocated to take either one of two different doses of vitamin D daily or a matching placebo for a year. The study will examine if these doses are effective at raising blood levels and are safe. The trial will assess the effects of vitamin D on blood levels of 25[OH]D, blood fats (lipids), biomarkers of inflammation, blood pressure, arterial stiffness and bone density. The results of this trial will help to select the optimal dose of vitamin D to be tested in a much larger trial assessing the effects of vitamin D on relevant disease outcomes. What are the possible benefits and risks of participating? It is unlikely that participants should gain materially or symptomatically from their participation in the study. However, the information resulting through their participation in the trial will be valuable for planning further larger trials of vitamin D assessing effects on major disease outcomes. The available evidence indicates that the doses of vitamin D used in the trial are likely to be safe and well-tolerated. In the unlikely event of any adverse effects, participants are advised to report any new unexplained symptoms to the study team, whose contact numbers are provided. These symptoms will also be evaluated at each study visit. Where is the study run from? The trial is being co-ordinated by the Clinical Trials Service Unit (CTSU), University of Oxford. The trial will be undertaken at a single GP practice, the Hightown Surgery, based in Banbury, Oxfordshire. When is the study starting and how long is it expected to run for? The study is expected to start in May 2012, and is anticipated to complete trial procedures by December 2013. Who is funding the study? University of Oxford (UK). Who is the main contact? Professor Jane Armitage [email protected]

Critère d'inclusion

• Safety and efficacy of vitamin D

Liens

• ictrp
• isrctn