Sir, – Dr Jacky Jones (Health + Family supplement, November 13th) claims "no one needs vitamin D supplements unless they stay indoors all day or wear clothes that completely cover every inch of skin". This dangerous advice contradicts the reality of vitamin D sources for populations of northern regions, including Ireland, where during winter months 55 per cent of the adult population are deficient or at high risk of vitamin D deficiency.
Vitamin D is critical for the healthy functioning of the human beyond just bone health (ie osteoporosis, as discussed in Dr Jones’s article, and rickets). In recent years, studies have shown the link between vitamin D deficiency and cancer, and autoimmune (eg multiple sclerosis), infectious and cardiovascular diseases. Moreover, vitamin D deficiency has been associated with poorer prognosis and survival in some cancer patients.
The main source of vitamin D is the production in skin following exposure to UVB from sunlight. However, in northern regions (including Ireland) the intensity of UVB is insufficient to induce skin synthesis from October to April, a period referred to as “vitamin D winter”. During this time very little (if any) vitamin D can be synthesised – even if one were to sunbathe for the whole day.
In Ireland, users of vitamin supplements have significantly higher Vitamin D levels compared to non-users. Dietary sources of vitamin D are scarce and insufficient to maintain healthy vitamin D levels; therefore, vitamin D supplements are by far the most important source for populations living at high latitudes – particularly in winter months. I, for one, took my supplement this morning. – Yours, etc,
LINA ZGAGA,
Associate Professor of Epidemiology,
Trinity College Dublin,
Dublin 2.