September, Sunshine and Vitamin D

(Please note: this diagram did not reproduce true, the shadow should be slightly longer than the stick and consequently the angle appears greater than 45 degrees.)

Here are some interesting facts, using a little basic trigonometry.

Today where I live, at 50 degrees 51’20” North Latitude, 1 degree 46’20” West Longitude , I measured the midday sun as about 44 degrees elevation above the horizon.  I placed a metre stick at a 90 degree angle to the ground and measured the length of the shadow it cast. The shadow was just slightly longer than the stick. This means the angle of elevation of the sun was just short of 45 degrees.  (Equal length of stick and shadow at right angles make the angle exactly 45 degrees.)

Obviously this is its maximum elevation during the day, and from here on in until six months’ time that angle will get shallower and shallower until the winter solstice, whence it will increase again.

The thing is, the sun needs to be at angle of 50 degrees or higher for UVA to penetrate the atmosphere. UVA is the ultraviolet wavelength responsible for stimulating Vitamin D formation in the skin. UVB on the other hand, which causes tanning and burning, can still penetrate at lower angles, so you can still tan and burn, but you won’t produce Vitamin D.

So for the next six months, at this latitude or higher, you will need to use a tanning bed or take Vitamin D supplements if you are to avoid deficiency.

For more information check out this article on Dr Joseph Mercola’s website: