Prolonged and severe deficiency of vitamin D can result in osteomalacia in adults. There is increasing evidence to show that vitamin D insufficiency (25(OH)D <50nmol/l) may also be involved in the development of chronic diseases and illness such as hypertension, diabetes mellitus, cardiovascular disease and some forms of cancers (Zittermann, 2003 & Holick, 2004). Most studies reporting a high prevalence of low vitamin D status have been carried out in the elderly. Data on younger adults is more limited, despite the fact that many of these chronic diseases originate in early adulthood.
Research on vitamin D status in younger Irish adults is currently scarce. In 2002, University College Cork carried out a vitamin D study where sub-groups of the Irish population were recruited. This was the first study carried out on a variety of age groups in Ireland, as most vitamin D studies are focused on the elderly Irish population. The aim of this study was to assess the prevalence of suboptimal vitamin D status in sub groups of the Irish population during the late-summer and late-winter/early spring. From this study, Hill et al, (2006) reported a clear seasonal effect on prevalence of low vitamin D status in adult Irish female subjects (aged 23-50 years). The prevalence ofvitamin D insufficiency (25(OH)D <50nmol/l) was more than 8-fold times higher in the winter compared with the summer (35% and 4%, respectively). Similar reports of low vitamin D status have been published (Lamberg-Allardt et al, 2001; Henderson et al, 2003; Barnes et al, 2006).
Recommendations for vitamin D in this age group range from 0-10μg/d in Ireland (FSAI, 1999) and in America the AI is 5μg/d (IOM, 1997). Many investigators believe these recommendations are too low to maintain an optimal vitamin D status. Hill et al, (2004) reported low vitamin D intakes in Irish adults, aged 18-64years, where the mean daily intake (MDI), from all sources, was 4.2μg/d. At present, in UCC, a double blind randomised intervention with vitamin D is being carried out in conjunction with the University of Ulster. The objective of this study is to establish a recommended daily allowance (RDA) of vitamin D for the Irish adult population. For more information see .