(Newswire.net — September 30, 2013) Malmö, Sweden —
Sunday September 29 was the last day this year when the sun managed to climb higher than 45 degrees above the horizon in NYC.
Now we have to wait until March 13 next year for its UVB-rays 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 time-table for the altitude of the sun.
Exposure of our skin to sunlight is the original source of vitamin D, but there must be UVB rays present in the sunbeams hitting the skin.
UVB comes with sunshine only when the sun is higher than 45 degrees above the horizon. It is when your shadow is shorter than you are tall.
When the sun is lower, the UVB-rays will be reflected or absorbed by the ozone-layer. Other hurdles, like, clouds, pollution or glass, will also block the UVB-photons.
In addition to the vitamin D creation, the UVB waves will also trigger melanin production. More melanin means a darker skin and a better sunburn protection.
Unfortunately, the UVB rays are also responsible for sunburns if you allow them too long exposure of unprotected skin.
Even without UVB from the sun, there is a way to get our vitamin D from UVB-exposure also during the “vitamin D winter”. Karl G Olson, an expert on how to use UV-exposure for vitamin D, explains how:
“If their lamps give enough UVB, sunbeds can be viable alternatives to the natural sun for vitamin D. A couple of “tanning” sessions every week is enough to keep a high vitamin D level also during the winter.
The session time for vitamin D tanning can be much shorter than for those who tan mainly for a dark skin-tone. This should eliminate any risk of sunburn.”
In this article, Karl G describes more in detail how to use sunbeds for vitamin D:
http://www.vitamindtanning.net/d-blog/vitamin-d-tanning-what-is-that/