New study on UV

MARY-JO TOHILL
Last updated 05:00 28/01/2013
Richard McKenzie
MARY-JO TOHILL
Emeritus scientists Richard McKenzie, left, and Paul Johnston, with a transportable UV spectroradiometer, designed and built at Niwa, which measures UV radiation in the atmosphere.
Richard McKenzie
MARY-JO TOHILL
Emeritus scientists Paul Johnston, left, and Richard McKenzie are doing unpaid work at Niwa's Lauder Station to understand the link between UV exposure and vitamin D.

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A soon-to-be released study at Niwa's Lauder Atmospheric Research Station near Alexandra will help answer the question about how much ultraviolet light exposure is needed to maintain people's vitamin D levels in the New Zealand winter.

For the past four years, Alexandra scientist Richard McKenzie has been collating data to investigate the health benefits and risks of UV exposure in the mid-latitudes, that is, in places like New Zealand, especially during winter months when UV levels are low.

Made redundant in a controversial job review at the National Institute Of Water and Atmospheric Research's (Niwa's) Lauder station last year, when three jobs, including his and colleague Paul Johnston's were axed, the now emeritus scientists are continuing to find the link between UV and vitamin D, the ''sunshine vitamin'', in blood -  for free.

When it became clear in 2006 that Niwa would not continue investing in ozone depletion and climate change from Lauder - the research that put the 51-year-old station on the map - they turned their attention to UV and health in the field of UV radiation, health and energy. 

''I still do atmospheric research but I must say I've gone away a bit from ozone research and moved more into UV and health,'' McKenzie says.

They became involved in the UVD study led by Professor Robert Scragg, of Auckland University, for the medical community, which posed a simple question: Do New Zealanders get enough UV in winter and, if not, should they be taking supplements to safeguard them from vitamin D deficient diseases, such as osteoporosis and possibly colon cancer?

Johnston and McKenzie elected to continue the study when they took redundancy, to assist colleague and Lauder scientist Ben Liley.

New Zealand's high melanoma rate was wellknown, but its vitamin D deficiency much less so, McKenzie said.

''We've got two problems in New Zealand, too much summer sun and not enough winter sun.''

Niwa data showed that New Zealand's peak UV Index values were 40 per cent more than in corresponding northern latitudes, which contributed to the country's high rate of melanoma.

In winter, UV is much weaker, only five to 10 per cent of that in summer, which contributes to low-levels of vitamin D, he said.

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However, an earlier study published by the Lauder group last year, contradicted current thinking that no vitamin D production occurred in winter when the long path of sunlight through the atmosphere blocks most of the available UV.

If McKenzie is right, then Otago and Southland people should be sun-seeking, unclothed, for at least 20 minutes - not very practical in New Zealand's coldest winter regions.

This also raised the question that if people could not get it from natural or artificial means and in what they eat (there's very little vitamin D added to New Zealand food) then how else could southern Kiwis get enough vitamin D to stay healthy?

Do vitamins do the same thing as UV rays entering the skin, which, through a chain of chemical process, ends up as vitamin D in the blood?

Scientists were still trying to understand what wavelength of light is most efficient at producing vitamin D, McKenzie said.

This much they do know: Too much sun and too little is equally bad. That's the curse and cure of UV.

''Actually, it's incredibly hard to get right. What's right for north Auckland is wrong for Southland. And what's right for Maori may be wrong for Pakeha and vice versa. And it's not as if there is a sudden switch between too much and too little. It depends on the actual UV, which is strongly peaked to the midday [highest sun] period.''

Scientists expect that with the Montreal Protocol's success on protecting the ozone layer, and because of increasing cloud cover related to climate change, UV levels would decrease slightly over the remainder of the century in the South Island.

If people stayed indoors more often as a result, this could have positive or negative impacts on health, McKenzie said.

With calculations being verified by population-based studies, final results of the study were nearing completion for publication in the near future, he said.

- The Southland Times

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