[The Au-Natural Health SIG] Vitamin D and Sunlight
Allison
Here's a short article from the UK talking about a rising incidence of Vitamin D deficiency due to people avoiding the sun because of fear of skin cancer. When exposed to sunlight, the body will make its own Vitamin D. It's possible to avoid the sun during peak hours, and still get enough sunlight for a healthy amount of Vitamin D.
EDP24 - Warning over vitamins and sunlight
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Posted By Allison to The Au-Natural Health SIG at 7/20/2007 04:11:00 PM
tedhutchinson
get enough sunlight for a healthy amount of Vitamin D.
I'd like start by pointing out our body's need for Vitamin D3.
This research http://www.ajcn.org/cgi/content/full/77/1/204
shows our bodies seem to use between 3000-5000 IU cholecalciferol
(vitamin d3) each day.
Unfortunately the current RDA is far too low
there is an urgent need to recommend a level that is effective see
http://www.ajcn.org/cgi/content/full/85/3/649
In the meantime when you read a report saying that it's possible to
make all the vitamin d your body needs from sunlight you have to
appreciate that person is almost certainly using the current RDA and
not up to date science based information regarding how much vitamin d
your body needs..
http://jcem.endojournals.org/cgi/content/abstract/87/11/4952?ijkey=166d2d70c6f4f0410d0f1032b1c17fca27a8382c&keytype2=tf_ipsecsha
This research shows men working outdoors all day in Omaho (wearing
normal clothing) actually achieve only 2800iu/daily thus during the
Winter they have insufficient status (remember not only is Omaha
nearer the Equator they also drink fortified milk in USA/Canada. We in
the UK are futher from the equator and do NOT have fortified milk.
http://www.uvguide.co.uk/vitdpathway.htm has a detailed description of
how vitamin d3 is made in the skin.
I'd like you to scroll down to the second diagram to see what happens
if you stay out in the sun too long .
I'd also like you to scroll right down that page to see the graphs of
when UVB is available through the day.
Having studied the page you will understand this is a heat driven
process.
If your skin temperature doesn't rise because the erythemal index is
below 3 then no vitamin d will be made.
Similarly if you are trying too hard to avoid peak hours you will miss
the essential UVB.
In practice your shadow has to be shorter than your height to be sure
there is UVB reaching the ground.
Laying down exposes more skin to the sun than standing up.
While in the UK the best ratio of UVB to UVA occurs round midday and
it is far better to obtain 20 minutes full body sun exposure then. 5
minutes full body exposure should raise 1000iu, turning over raises
another 1000 and repeating the process totals 4000iu sufficient to
last one day.
If you need to rectify a deficiency situation or build up stores for
the Winter then rather than continuing for longer it would be better
to allow time for the vitamin d on your skin to be absorbed and the
skin to cool before repeating the process. Too much heat turns excess
vitamin d into suprasterols which the body has no use for.
This research http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=17637484
shows it is possible to build up your Vitamin d status by using UVB
producing sunlamps but you would need to persist with 3 times weekly
session for longer than a month in order to reach a healthy plateau
however this was trying to achive useful increases in vitamin D status
with UVB doses small enough to produce only minimal tanning.