IT TURNS OUT the Irish weather provides enough vitamin D during the winter months, contrary to popular belief.
A new study from Trinity College Dublin shows Irish sunshine is not too weak to encourage vitamin D production in the skin during the ‘vitamin D winter’ of October to April.
Using data from European Space Agency (ESA) satellites to measure UVB levels over Ireland, the researchers found that a strong relationship between sunshine and vitamin D persist beyond summertime.
It was the first time these satellites were used in research on vitamin D and UVB exposure or personalised to this extent in a study.
The amount of vitamin-D-producing UVB is reduced at higher latitudes, such as Ireland, but sunshine still contributes to vitamin D levels throughout the year, even from October to Apri. Fiona O’ Sullivan, a PhD student working on this project said:
While UVB levels are much less in the colder part of the year, they are far from zero.
Location, Location
Even though Ireland is a relatively small country, large differences in ambient UVB between the North and South of the country were found –19% higher yearly UVB in Mizen head than Malin head.
There were also considerable differences between the East and West of the country, especially in the summer time, giving greater meaning to the popular phrase ‘The Sunny South East’.
The ability to synthesise vitamin D in the skin is known to decrease with age. Some 5,138 people in Ireland aged 60 and over took part in the study.
Lead researcher and an Associate Professor of Epidemiology in Trinity College Dublin, Dr Lina Zgaga, said:
We were able to measure, based on where they lived, the amount of exposure they got to sunshine over the previous five months, and analyse how important their exposure to sunshine was to their levels of vitamin D.
The study also confirmed a dramatic impact of supplementation on maintaining a healthy vitamin D status.
“It is difficult to prescribe sunshine, as too much is a risk for skin cancer, and too little is a risk for vitamin D deficiency” Dr Zgaga said.
It is much easier to follow black-and-white advice, such as do eat vegetables and do not smoke. With sunshine, everyone needs to aim for their personal ‘right amount’, which unfortunately changes all the time.
It was also found that people over 60 year who avoided the sun had much lower levels of vitamin D and were at risk of deficiency, compared to those who enjoy sunshine. O’Sullivan added:
In fact those who enjoy sunshine managed to avoid severe vitamin D deficiency, even if they were not taking supplements.
“These findings are especially important as the prevalence of vitamin D deficiency in Ireland is quite high, especially among the elderly, and although it might not seem like we get a lot of sunshine, in actual fact the sunshine we do get is still a very important source of vitamin D.”
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