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Originally Posted by deb34
I always thought something bad happens to the D3 when you burn your skin even only slightly. I have no idea where I got that understanding from but that's why I've been very careful to not even burn slightly- D3 turns on you if you get burned even slighty- maybe one of the experts here could comment on my theory?
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I believe that burning is mostly a condition of D deficiency to begin with (as well as A, perhaps, as well). In one of the D council's newsletters, they mention that part of the activity that the D metabolites carry out is protection of the skin from UV damage, and I believe even Zuleikaa has mentioned before that inability to tolerate sun is an additional deficiency symptom. And I know Demi has also posted testament previously that obtaining adequate D resulted in protection from burning while tanning. I experience the same results when obtaining enough substrate D3.
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Being in the sun helps protect you from being in the sun. True or False?
True. Dr. Dixon at the University of Sydney, working with Professor Rebecca Mason's group, has presented additional evidence that vitamin D metabolites protect the skin from sun damage, and do so via rapid acting pathways that do not involve genetic transcription. As anyone who has ever taken 5,000 IU a day for several months can tell you, your skin is much less likely to burn when you are no longer vitamin D deficient.
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In vivo relevance for photoprotection by the vitamin D rapid response pathway
Skh:hr1 mice exposed to three times the minimal erythemal dose of solar-simulated UVR and treated topically with 1,25(OH)(2)D(3) or JN immediately after UVR showed reduction in UVR-induced UVR-induced sunburn cells (p<0.01 and <0.05, respectively), CPD (p<0.01 for both) and immunosuppression (p<0.001 for both) compared with vehicle-treated mice. These results show for the first time an in vivo biological response mediated by a rapid-acting analog of the vitamin D system. The data support the hypothesis that 1,25(OH)(2)D(3) exerts its photoprotective effects via the rapid pathway and raise the possibility that other D compounds produced in skin may contribute to the photoprotective effects.
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The Vitamin D Newsletter August 2006 | Dr. Cannell Answers More Readers' Questions
If you are scientific, try a little experiment. Take someone you know with fair skin who burns easily and who doesn't go in the sun. Take him or her into a sun tan booth and find out exactly how many minutes it takes for their skin to just begin to turn pink, called one minimal erythemal dose (MED). Then, keep them out of the sun but give them 10,000 units of vitamin D a day for a month. Then take them into the sun tan booth again and see how long it takes for them to get one MED. What you will discover is that their time for one MED is longer. High vitamin D blood levels help prevent burning and facilitate tanning.
My teenage daughter, who used to burn easily, discovered this. Against my advice, she took 5,000 units of vitamin D every day and regularly went into a sun tan booth as well. Now all her friends are begging her to tell them why she never burned and got so incredibly tan, tanner than she ever got before. Furthermore, burning in vitamin D deficient people actually may have an evolutionary benefit. Burning heats the skin and the final step in the production of vitamin D is driven by high skin temperatures. It also makes evolutionary and physiological sense that high vitamin D blood levels would facilitate rapid tanning and thus protect against vitamin D toxicity. Just remember, burning is dangerous and should always be avoided.
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I'm actually back up to 20K IUs per day right now and the improvement is pretty pleasing. Even 10K IUs wasn't enough to flip the switch for me and get me where I was feeling 'normal' or even close to normal and not burn and feel poisoned by UV light. Now at my higher dose, my gums are doing much better, my skin is improved, and I can get all the sun I want practically without fear of getting burned or crispy. Even Holick believes that an optimal full body exposure to mid-day sun will produce upwards of 20K IUs after a single exposure of adequate time (30 minutes or so). The D council also mentions studies where upwards of 50K IUs have been observed after sun exposure.
I applaud the D council and scientists alike for the push to break down these walls of woefully inadequate intakes/exposures, but even their more liberal recommendations still don't seem to be hitting the mark for me. When combined with all the synergistic nutrients (A, E, K2, calcium, magnesium, minerals in general, iodine, etc.), one can avoid any concerns of toxicity even at remarkably higher doses and the results can be greatly amplified.
Zuleikaa, I have a document where I collected many a posts that I found interesting from this thread to keep for my personal collection. One of them had a post from you that mentioned that there was evidence that it was being understood that the D wasn't being destroyed to the extent once believed when getting continual sun exposure, justifying the fact that we are designed for higher D production/intake than is commonly believed. Might you be able to cite more specific resources as to where you come to this conclusion and posted the following in a previous D experiment thread of the past (on 02/09/2006)? No worries if not, just interested in looking into that further.
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Originally Posted by Zuleikaa
The higher hurdle for vitamin D deficiency makes more sense to me in light of the vitamin D status of people native to the tropics; they have vitamin D levels ranging from 125 nmol/L to 200 nmol/L. Further, they've now discovered that the body doesn't just shut down vitamin D production but can produce in excess of 50,000 IUs of vitamin D per day. I know of that 50k+ some is stored for winter but, in that case, to me, a higher level RDA makes even more sense.
To me having a FDA mandated "safe" level of 2,000 IUs when your own skin can produce in excess of 50,000 IUs of vitamin D per day during the summer from prolonged or repeated exposure is ridiculous.
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Amen to the last part! Thanks! 
Edited to include this that I found in one of the original threads:
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Post #60 from Nov. 2005
Vieth (4) estimates that the physiologic limit for daily vitamin D intake is 250–500 µg (10 000–20 000 IU/d). This amount also makes sense from a physiologic standpoint because this daily vitamin D load (10 000–20 000 IU) would be easily achieved from ultraviolet (UV) light–induced cutaneous synthesis in subjects of all races who work outside in sun-rich environments (22-25).
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Edited to include this from the same post, which pretty much answers my question:
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Humans have evolved at exposures of > 20 000 IU (500 µg) vitamin D/d from the sun. In fact, a 0.5-h exposure to the summer sun between 1000 and 1400 in a bathing suit (3 times the minimal erythemal dose) will initiate the release of 50 000 IU (1.25 mg) vitamin D into the circulation within 24 h of exposure in white persons (25). African Americans require up to 5 times this solar exposure to achieve the same response (26, 27). In whites who have a deep tan because of melanin deposition in the skin, the response is 50% of that stated above, ie, only 20 000–30 000 IU (500–750 µg) vitamin D will be liberated (28). Finally, if wearing clothing or total body sunscreen, the cutaneous release of vitamin D is completely blunted (24, 29-31). So, in light of the above facts, a DRI of 400 IU/d (10 µg/d) in adults seems woefully inadequate to maintain normal circulating concentrations of vitamin D in adults with minimal solar exposure.
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