There is a lot of hype put about regarding the dangers of sun exposure
put about by those profiting from the cancer creation industry.
Remember for each person who dies of skin cancer 30 excess deaths
occur in the most common cancers breast prostate lung colon, These and
13 other cancers thrive in vitamin d depleted bodies.
Applying sunscreen/sunblock prevents UVB rays from reaching the skin.
Putting it on before you go out therefore totally prevents any vitamin
d being made.
This is why the average European woman has Vitamin d status around
50nmol/L, the level needed for maximum calcium absorption is 80nmol/L
and to have 50% less breast cancer it's best to have 130nmol/L. If the
advice from "Official" sources was correct we would not have the
current deficiency epidemic. 9 out of 10 UK White adults are below
75nomol/l in Winter and 60% remain so the whole year. If you take the
official RDA vitamin D and follow official RDA advice you will be
vitamin d deficient. Similarly if you rely on your doctor to correct
that deficiency you will be ill advised as they generally prescribe D2
Ergocalciferol and The Case Against Ergocalciferol as a Vitamin
Supplement explains why. http://www.ajcn.org/cgi/content/full/84/4/694

http://www.ncbi.nlm.nih.gov/sites/en...rch=1 7259988
DCs metabolize sunlight-induced vitamin D3 to 'program' T cell
attraction to the epidermal chemokine CCL27. explains how when UVB
rays touch your skin the first thing the newly made Vitamin D3 does is
to program your "T"Cells to start fighting skin cancer.

Vitamin D synthesis is a heat driven self-limiting process. This means
you need an erythemal index above 3 and UVB rays. These are only
present when your shadow is shorter than your height and if you live
above latitude 37 during the summer. The self-limiting bit means that
once the cholesterol in your skin is converted to vitamin d3 it then
should further heat be applied, be further processed into
suprasterols. These are not used. So to maximise your vitamin D
production you need to GO INSIDE or COVER UP after 20 minutes. (you
will make 1000iu every 5 minutes so 20 minutes full body (or near as
possible) exposure provides the amount you use daily. If you are
trying to build stores for the Winter or rectify a deficiency
situation then wait an hour for your skin to cool and the vitamin d to
be absorbed then try for another 15 mins. But be aware 10,000iu is
about all that the body usually makes each day so is a natural
maximum. So 1x 20 + 2 x 15mins exposures are around the most anyone
can benefit from.