J Clin Endocrinol Metab. 1988 Aug;67(2):373-8.
Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin.
Webb AR, Kline L, Holick MF.
Sunlight has long been recognized as a major provider of vitamin D for humans; radiation in the UVB (290-315 nm) portion of the solar spectrum photolyzes 7-dehydrocholesterol in the skin to previtamin D3, which, in turn, is converted by a thermal process to vitamin D3. Latitude and season affect both the quantity and quality of solar radiation reaching the earth's surface, especially in the UVB region of the spectrum, but little is known about how these influence the ability of sunlight to synthesize vitamin D3 in skin. A model has been developed to evaluate the effect of seasonal and latitudinal changes on the potential of sunlight to initiate cutaneous production of vitamin D3. Human skin or [3 alpha-3H]7-dehydrocholesterol exposed to sunlight on cloudless days in Boston (42.2 degrees N) from November through February produced no previtamin D3. In Edmonton (52 degrees N) this ineffective winter period extended from October through March. Further south (34 degrees N and 18 degrees N), sunlight effectively photoconverted 7-dehydrocholesterol to previtamin D3 in the middle of winter. These results quantify the dramatic influence of changes in solar UVB radiation on cutaneous vitamin D3 synthesis and indicate the latitudinal increase in the length of the "vitamin D winter" during which dietary supplementation of the vitamin may be advisable.
J Lab Clin Med. 1989 Sep;114(3):301-5.
In vivo threshold for cutaneous synthesis of vitamin D3.
Matsuoka LY, Wortsman J, Haddad JG, Hollis BW.
Cutaneous vitamin D3 synthesis and release into the circulation is promoted by skin exposure to ultraviolet B radiation (UVB, spectrum 290 to 320 nm). To determine the relation between UVB energy level and cutaneous vitamin D synthetic response, we delivered graded increases of UVB suberythemic radiant energy (3 to 27 millijoules/cm2 [mJ/cm2]) to 32 untanned young white subjects with skin type III (Fitzpatrick-Pathak classification). Serum vitamin D3 was determined 1 hour before (basal value) and 24 hours after a single whole body exposure to UVB in a phototherapy unit. The basal vitamin D3 concentration was similar in all individuals (mean +/- SEM for whole group, 1.6 +/- 0.2 ng/ml). UVB irradiances were followed by proportional rises in serum vitamin D3 (at 27 mJ/cm2, 14.3 +/- 3.7 ng/ml), and the overall correlation between UVB radiation and consequent serum vitamin D3 response (r = 0.81; p less than 0.02) was best described by an exponential function. The minimal UVB radiation level that produced a significant increase in serum vitamin D3 was 18 mJ/cm2, a value similar to the lowest solar broadband UVB irradiance that generates previtamin D3 in vitro from the precursor 7-dehydrocholesterol (20 mJ/cm2). Because in the northern United States winter UVB irradiance does not generally reach this threshold level, we conclude that individuals living at extreme northern (or southern) latitudes may have higher dependence on body stores and dietary supply to meet their vitamin D requirements during winter.
Who has Blindguru?
Everyone has this inner-knowning at birth. It is not the 5 senses that we are used to using. It is the "gut" feeling. This is a highly ignored innate sense. This sense cannot be found by reading any book. Many people are searching for answers in a book. The health and wellness books that are sold in bookstores that are written for the mass do not have the answers. We look to nature and find our answers based on our intuition. We do not ask others for answers but are open to educating ourselves and using our pre-cognition for our answers.
The best way to find your own Blindguru is to build an alkaline, aerobic body and your own body will guide you. It is extremely hard to want to eat intuitively if you do not have the 3 to 5 lbs of aerobic bacteria in your body. Most people can't even begin to use their innate intuition unless they can utitlize their aliesthetic sense. Inner knowing is the most popular reference. Believing without seeing with the subconscious mind (Body mind).
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