Vitamin D tool

Making a complex message a little easier ....

A couple of colleagues in Australia have come up with a nifty on-line tool to tell you how long you need to be in the sun to get enough UV to maintain your levels of vitamin-D. It’s based on a paper I discussed recently.

A screen-shot of the tool is shown below (but the dynamic on-line version is much better)

Although the paper it’s based on does include New Zealand sites, the tool unfortunately gives times only for Australian sites. But, for New Zealand, you can get a good idea by taking the city with the most similar latitude. For example, Auckland’s latitude is close to Melbourne’s. And Christchurch’s latitude is similar to Hobart’s.

Or, you could use one of our smartphone apps which provide similar information for the current day at any site in New Zealand (using the UVNZ app), or at any site in the world at any time (using the GlobalUV app).

The main messages are that in summer, when the risk of UV damage to your skin is high, the times required for vitamin D sufficiency are much less than those leading to skin damage. Typically, less than 5 minutes exposure at midday is more than enough. Some studies even suggest that longer exposures may compromise your vitamin D levels. In winter it’s more problematic. Some supplementation may be advised if you’re living at latitudes more than about 40 degrees from the equator. Talk to your doctor if you’re concerned.