Midden op de dag kort in de zon

Zon is wel goed voor je. Maar kort en als de zon op zijn hoogst staat!

De modernste inzichten van de effecten van ultra violet licht op onze huid zijn verandert. Ten eerste is gebleken hoe belangrijk de eigen vitamine D productie voor de gezondheid is, en die is maximaal gedurende de tijd dat de zon op zijn hoogst staat. De kans op huidkanker is lager als je kort zont, zonder te verbranden rond 12 uur, dan dat je langer in de zon ligt, later op de dag zonder lichte verbrandingenen. Onderzoekers van het 'department of Radiation Biology; van het 'Institute for Cancer Research' in Noorwegen hebben in 2008 nieuwe inzichten vermeld op dit terrein. We citeren:

To get an optimal vitamin D supplement from the sun at a minimal risk of getting cutaneous malignant melanoma (CMM), the best time of sun exposure is noon.

Thus, common health recommendations given by authorities in many countries, that sun exposure should be avoided for three to five hours around noon and postponed to the afternoon, may be wrong and may even promote CMM.

The reasons for this are

(1) The action spectrum for CMM is likely to be centered at longer wavelengths (UVA, ultraviolet A, 320-400 nm) than that of vitamin D generation (UVB, ultraviolet B, 280-320 nm).

(2) Scattering of solar radiation on clear days is caused by small scattering elements, Rayleigh dominated and increases with decreasing wavelengths. A larger fraction of UVA than of UVB comes directly and unscattered from the sun.

(3) The human body can be more realistically represented by a vertical cylinder than by a horizontal, planar surface, as done in almost all calculations in the literature. With the cylinder model, high UVA fluence rates last about twice as long after noon as high UVB fluence rates do.

In view of this, short, nonerythemogenic exposures around noon should be recommended rather than longer nonerythemogenic exposures in the afternoon. This would give a maximal yield of vitamin D at a minimal CMM risk.

Dus kort in de zon in het vroege middaguur! [1]