The Vitamin D Winter Starts Now
Exposure of your skin to sunlight is the original source of vitamin D.
But not any sunlight will trigger the vitamin D synthesis. There must be UVB rays present in the sunbeams hitting your skin.
The UVB-waves are shorter than the UVA (The UVA contributes to your natural sun-protection by making the pigment, melanin, already existing in your skin, darker and the skin thicker.)
Unfortunately, the UVB rays are also responsible for you getting a sunburn if you allow them through too long exposure of unprotected skin.
UVB comes with sunshine only when the sun is higher than 45 degrees above the horizon (some researchers say 50 degrees, others 45. It is not like turning on or off a switch but a gradual decrease of UVB). 45 degrees is when your shadow is shorter than you are tall.
When the sun is lower in the sky, some of the UVB will be reflected by the ozone-layer and the rest will be absorbed (diffused) because of a longer path through the ozone-layer.
Other hurdles, like, clouds, pollution or glass, also filter away the UVB-photons.
Only clear, undisturbed, sunlight from a sun higher than 45 degrees in the sky will bring the necessary UVB to your skin for the vitamin D production to begin.
The problem is that for the many of us living away from the equator, the sun ends coming higher than 45 degrees already sometime during August or September (on the Northern hemisphere) and stays low for several months.
As an example, for the city of Copenhagen, the capital of Denmark, the vitamin D winter starts on August 25 this year. That is the day when the sun manages to climb higher than 45 degrees (at least for a couple of minutes around one o’clock) for that last time until around mid-April next year.
In the graph below you can see when the sun is higher than 45 degrees for this location. Other places around the world which are located at approximately the same latitude with approximately the same graph, are: Edinburgh and Glasgow in the UK; James Bay and Ketchikan in Canada; Moscow, Lake Baikal and Petropavlosk-Kamchatka in Russia.
The graph also shows between which time of the day the sun is above 45 degrees for different dates. The hours are set for European daylight-saving time (summer-time).
You can easily do the calculation for your place, using the method I outlined in this article: Do You Know How To Tan?
However, if you want me to do it for you, simply click on the “DONATE” button below the image and send me the amount you think it is worth to save you the time to do it yourself. I will then send you the graph to your PayPal email address you used for the donation. Don’t forget to use the PayPal message-field to give your location (city/place, province/region, country).
Below is the graph for New York. If you live there, you have until September 29 to catch some vitamin D in the way Mother Nature intended it – by exposing your skin towards UVB-rays. After September 29, you have to wait until March 13 for the sun to climb above 45 degrees and its UVB to reach the earth again (at least in sufficient amount to give you vitamin D within a reasonable exposure-time). Salt Lake City is another place on the same latitude (parallel) as New York, with (approximately) the same graph for the altitude of the sun.
The blue line represents the time of the day that sun starts to appear higher than 45 degrees above the horizon and the red line shows when it drops below the “vitamin D altitude”.
Do you want me to do the calculation for your place and send an image with a graph according to the same model as above to your PayPal email address? Then just click on the “Donate” button below and send me the amount you think it is worth.