May Day in the heat

Such glorious weather. Since returning home to Warsaw on Saturday night, the weather has remained perfect. Hot and dry - the weather one would wish for on the ideal holiday. And coinciding with Poland's longest public holiday - 1 and 3 May (both days off work) happen on a Tuesday and a Thursday, so by taking three days off work, you can get a nine-day break. Which many Varsovians have, judging by the reduced volume of traffic in town.

No mosquitoes or other insects to trouble one, low humidity. Time to step out and enjoy the midday sun. Are we getting to paranoid about it? An article in New Scientist (10 April 2012) suggests that we have become so worried about the risk of skin cancer brought on by over-exposure to the sun that we are missing out on the health-giving benefits of Vitamin D, made in the skin when exposed to sunlight.

Vitamin D seems to play a key role in keeping the immune system in check so that it doesn't react to things inappropriately. [There is a] higher rate of autoimmune disorders in parts of the world with less sunlight... vitamin D suppresses the immune system by inhibiting the proliferation of immune cells and the signalling factors that spur them into action. Sunshine's effects stretch beyond those of vitamin D. Melatonin – a hormone secreted by a gland in the brain in response to changes in light – stimulates immune cells. Vitamin D is also vital for calcium absorption and bone health. Unfortunately, growing awareness of the risks of skin cancer has led some people to shun the sun, hence a recent resurgence in childhood rickets. Skin cancer aside, vitamin D appears to protect against many other common types of cancer, including those of the breast, prostate and colon. One research group has calculated that in the US, more people die from internal cancers caused by lack of sun exposure than from skin cancer itself – possibly four times as many.

Now, as well as protecting myself from sun, my habit is to wear long trousers and long sleeves to protect myself against ticks (not a problem in the UK, but in leafy Warsaw suburbs, something to be aware of from April to September). Maybe I need a healthier dose of sunshine - but how much is healthy?

Michael Holick, a vitamin D researcher at Boston University in Massachusetts, says you should expose your hands, arms and face for a quarter of the time it would take to cause reddening two to three times a week.

This is just one scientist's opinion, but this does seem reasonable - to find a balance between pit-pony pale and lobster red. So today, I ventured forth into to the midday sun* for exactly one hour, in a T-shirt and jeans, to see whether there'd be any reddening... no. No visible contrast between skin under watch strap and wrist. So 15 minutes two to three times a week might not enough for me. (Next time an experimental 90-minute dose will be required).

And just how hot and sunny was it today? At 13:00 the temperature was 31C, air humidity a mere 24%! The sky was clear, with just some small fluffy clouds here and there.

Above: looking across the fields next to our house. I have selectively desaturated the photo to get the same look and feel as Roger Deakins achieved in the Coen Brothers' film O Brother Where Art Thou; at this time each year I feel an intense urge to see it again...

* Because of daylight-saving time, the sun is directly overhead at 13:00 rather than at noon for the seven months between the last weekend of March and the last weekend of October.

This time last year:
Bike ride across rural Poland

This time five years ago:
Mazovian landmark from the air