# Sunshine, vitamin D, and showering: what's the real deal? **URL:** \ **Category:** Factual Questions\ **Created:** [May 16, 2009, 3:23am UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609 "2009-05-16T03:23:18Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![bink](https://avatars.discourse-cdn.com/v4/letter/b/439d5e/32.png) [@bink](https://boards.straightdope.com/u/bink)\ **Post date:** [May 16, 2009, 3:23am UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/1 "2009-05-16T03:23:18Z")
So I’ve read somewhere \ that you’re not supposed to shower right after you come in from the sun because you’ll wash all the Vitamin D off before it gets absorbed by your body. How long do you have to wait? I consulted Dr. Google. One site says 20 minutes, one site says an hour, one site says 48 hours but helpfully suggests that you can bathe your stinky bits during that time as long as you don’t use soap on your extremities that were exposed to the sun. But what happens when you towel off? Does anybody know the real answer? ---
**Author:** ![Finagle](https://avatars.discourse-cdn.com/v4/letter/f/b19c9b/32.png) [@Finagle](https://boards.straightdope.com/u/Finagle)\ **Post date:** [May 16, 2009, 4:05am UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/2 "2009-05-16T04:05:59Z")
This seems incredibly unlikely. Vitamin D generation (according to Wikipedia) takes place in the bottom-most layer of the epidermis. Further, it is fat soluble, so water alone would be unlikely to remove it. (Which, I guess, means if you’re really worried about this, skip the soap.) But my guess would be that you’re about as unlikely to wash off vitamin D as you are to wash off your tan. One caveat – animals with fur or feathers generate vitamin D as an oily secretion which is then ingested during grooming. So your pet bird probably shouldn’t shower until it’s gotten its daily dose of vitamin D. ---
**Author:** ![Mr\_Buttons](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@Mr\_Buttons](https://boards.straightdope.com/u/Mr_Buttons)\ **Post date:** [May 16, 2009, 4:06am UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/3 "2009-05-16T04:06:03Z")
I’ve always been under the impression that the vitamin D is created within your body from the UV rays or whatever. The sun isn’t beaming out Vitamin D to the entire universe. I’ve never ever heard that you could wash off the Vitamin D, I think you’re info is severely flawed. ---
**Author:** ![Mr\_Buttons](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@Mr\_Buttons](https://boards.straightdope.com/u/Mr_Buttons)\ **Post date:** [May 16, 2009, 4:19am UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/4 "2009-05-16T04:19:46Z")
Here’s a wiki link. [Wiki: Vitamin D production in skin](http://en.wikipedia.org/wiki/Vitamin_D#Biochemistry) I didn’t spend enough time studying dermatology to learn all our hormones and stuff, but what I could grasp basically says: UVB light from sun -\> animal skin -\> process to create Vitamin D. As a Finagle said, that would make it about as easy to rub off as a tan. 🙂 > [@](#): > > Vitamin D is a prohormone, meaning that it has no hormone activity itself, but is converted to the active hormone 1,25-D through a tightly regulated synthesis mechanism. Production of vitamin D in nature always appears to require the presence of some UV light; even vitamin D in foodstuffs is ultimately derived from organisms, from mushrooms to animals, which are not able to synthesize it except through the action of sunlight at some point in the synthetic chain. For example, fish contain vitamin D only because they ultimately exist on calories from ocean algae which synthesize vitamin D in shallow waters from the action of solar UV. I’ll leave it to an MD or Dermatologist to elaborate. ---
**Author:** ![Alex\_Dubinsky](https://avatars.discourse-cdn.com/v4/letter/a/dbc845/32.png) [@Alex\_Dubinsky](https://boards.straightdope.com/u/Alex_Dubinsky)\ **Post date:** [May 16, 2009, 6:03am UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/5 "2009-05-16T06:03:09Z")
> [@Finagle](#): > > One caveat – animals with fur or feathers generate vitamin D as an oily secretion which is then ingested during grooming. So animals need to lick their dirty fur to get this vital nutrient? That’s pretty surprising in itself. Maybe this idea has some legs, unless our entire vitamin D subsystem changed ever since we got naked (very very recently). For all it’s worth, I like licking salty things and if this is one more reason to do so… EDIT: Ok, read the Wiki article. But who’s to say much of _our_ vitamin D isn’t also produced in the surface oils, instead of inside the skin. And that we should lick it… ---
**Author:** ![ToeJam](https://avatars.discourse-cdn.com/v4/letter/t/dfb087/32.png) [@ToeJam](https://boards.straightdope.com/u/ToeJam)\ **Post date:** [May 16, 2009, 6:16am UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/6 "2009-05-16T06:16:59Z")
> [@Alex\_Dubinsky](#): > > So animals need to lick their dirty fur to get this vital nutrient? That’s pretty surprising in itself. Maybe this idea has some legs, unless our entire vitamin D subsystem changed ever since we got naked (very very recently). For all it’s worth, I like licking salty things and if this is one more reason to do so… 7-dehydrocholesterol is a naturally produced derivative of Cholesterol in most people. Your body just needs to use the UV light from the sun to convert to to Vitamin D3. (well, it actually converts to a form known as Pre-vitamin D3, but then spontaneously undergoes isomerization in the body to become Vit D3 known as cholecalciferol. That form is actually stored in your liver then, and released as needed to help with Calcium absorption in a form known as calcitriol and basically helps to increase the amount of calcium your body retains during digestion (to help increase circulating Calcium Plasma levels). Most people would know if they have calcium deficiencies and all just from regular doctor visits (and more of a concern for those with diminished calcium levels), but if someone REALLY wanted to supplement their diet to increase the Vitamin D, they could try eating certain fish or eggs I believe rather than just trying to “lick salty things”. But again, it’s not really something to worry about too much- if you get 20 mins of sunlight a Day, that’s good enough to move the reaction along to the next step- and you’ll be storing it in your liver for a while as well. \*Edit on Preview: Okay… lick away then. Fair enough. But it doesn’t quite work that way. If you’ve got a healthy supply of cholesterol in your body, and you’re getting the 20 mins of sunlight, you’re good to go. ---
**Author:** ![Alex\_Dubinsky](https://avatars.discourse-cdn.com/v4/letter/a/dbc845/32.png) [@Alex\_Dubinsky](https://boards.straightdope.com/u/Alex_Dubinsky)\ **Post date:** [May 16, 2009, 6:51am UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/7 "2009-05-16T06:51:35Z")
> [@Ro0sh](#): > > and you’re getting the 20 mins of sunlight A lot of people don’t get 20 minutes of sunlight every day. (Do you?) Especially in the winter. Especially in northern latitudes. Vitamin D insufficiency is an under-recognized problem that results, for a lot of people, in depression. (And that comes on a lot sooner than osteoporosis or low blood calcium, so the “routine checkup will tell you everything” suggestion is incorrect.) Of course, it might be better treated with supplements than licking… ---
**Author:** ![Mr\_Buttons](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@Mr\_Buttons](https://boards.straightdope.com/u/Mr_Buttons)\ **Post date:** [May 16, 2009, 6:57am UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/8 "2009-05-16T06:57:29Z")
> [@Alex\_Dubinsky](#): > > A lot of people don’t get 20 minutes of sunlight every day. (Do you?) Especially in the winter. Especially in northern latitudes. Vitamin D insufficiency is an under-recognized problem that results, for a lot of people, in depression. (And that comes on a lot sooner than osteoporosis or low blood calcium, so the “routine checkup will tell you everything” suggestion is incorrect.) Of course, it might be better treated with supplements than licking… Gah, I was really trying to avoid mentioning this… but I’m looking at you MMORPG people (WoW, FFXI, LotR, etc.) I had a 2 year addiction to FFXI, and I’m pretty sure that sucked out a lot of vitamin D. 😛 ---
**Author:** ![Mr\_Buttons](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@Mr\_Buttons](https://boards.straightdope.com/u/Mr_Buttons)\ **Post date:** [May 16, 2009, 6:58am UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/9 "2009-05-16T06:58:49Z")
> [@Alex\_Dubinsky](#): > > A lot of people don’t get 20 minutes of sunlight every day. (Do you?) Especially in the winter. Especially in northern latitudes. Vitamin D insufficiency is an under-recognized problem that results, for a lot of people, in depression. (And that comes on a lot sooner than osteoporosis or low blood calcium, so the “routine checkup will tell you everything” suggestion is incorrect.) Of course, it might be better treated with supplements than licking… Gah, I was really trying to avoid mentioning this… but I’m looking at you MMORPG people (WoW, FFXI, LotR, etc.) I had a 2 year addiction to FFXI, and I’m pretty sure that sucked out a lot of vitamin D. 😛 Damn sunlight is blocking 75% of my screen! Close the blinds! 😃 ---
**Author:** ![bink](https://avatars.discourse-cdn.com/v4/letter/b/439d5e/32.png) [@bink](https://boards.straightdope.com/u/bink)\ **Post date:** [May 16, 2009, 4:05pm UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/10 "2009-05-16T16:05:12Z")
Hey, I wouldn’t want to stop anyone from licking salty things! But if it all happens inside, not a layer of oil on the skin, then that’s good to know. Here’s [Mercola](http://articles.mercola.com/sites/articles/archive/2009/05/12/Shocking-Update-Sunshine-Can-Actually-Decrease-Your-Vitamin-D-Levels.aspx) saying to wait 48 hours (warning, video starts to play on that page). Here’s [Weston A. Price](http://www.westonaprice.org/basicnutrition/vitamindmiracle.html) saying to wait one hour. Then there are a ton of links [here](http://blog.nutritiondata.com/ndblog/2008/07/can-you-store-u.html), most of which agree with the posters here and debunk the wait-to-shower concept. ---
**Author:** ![Furious\_Marmot](https://avatars.discourse-cdn.com/v4/letter/f/dfb087/32.png) [@Furious\_Marmot](https://boards.straightdope.com/u/Furious_Marmot)\ **Post date:** [May 16, 2009, 4:31pm UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/11 "2009-05-16T16:31:39Z")
> [@Alex\_Dubinsky](#): > > Vitamin D insufficiency is an under-recognized problem that results, for a lot of people, in depression. Got a peer-reviewed citation for that? ---
**Author:** ![ToeJam](https://avatars.discourse-cdn.com/v4/letter/t/dfb087/32.png) [@ToeJam](https://boards.straightdope.com/u/ToeJam)\ **Post date:** [May 16, 2009, 6:17pm UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/12 "2009-05-16T18:17:09Z")
> [@Furious\_Marmot](#): > > Got a peer-reviewed citation for that? I was just going to go to Wikipedia and get a look at that claim, as there were quite a few claims for what Vit. D could cause (but yeah, the major problems for Vit D insufficiency is Bone disorders- the big 3 being Rickets, Osteomalacia, and Osteoporosis. Also, turns out that the US fortifies it’s milk w/ Vitamin D, so one less worry about the need for the fishy foods and licking of salty things if you drink your American Milk- though you’d still need the sunlight). Anyways, so I clicked on the cited article for where Vit D may be related to depression on wikipedia… and was quite surprised. It turns out the [Cited article](http://www.springerlink.com/content/h5q5rb2lpetmf8gn/) ACTUALLY STATES THE opposite. :smack: That’s just terrible… I mean sure they “may” be related, but then why cite an article that states it couldn’t FIND a link between the two? Bad Wiki, bad! But yeah- okay, if you’re not getting the 20 mins of sunlight- then you need to think about supplements, but in that case ordinary Vitamin D wouldn’t help you- you’d need the ACTIVATED form of Vitamin D3, which have a half life if I recall of around 20 days to a month- because if it’s the sunlight that’s an issue that’s a step in the Vitamin D activation, getting the inactive form orally does nothing for you if Sunlight’s the problem. So if you’re supplementing yourself, make sure you’re getting the right form that you need: cholecalciferol. ---
**Author:** ![Qadgop\_the\_Mercotan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/qadgop_the_mercotan/32/83_2.png) [@Qadgop\_the\_Mercotan](https://boards.straightdope.com/u/Qadgop_the_Mercotan)\ **Post date:** [May 16, 2009, 6:24pm UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/13 "2009-05-16T18:24:09Z")
Some good links to Vitamin D facts here: [how fast do vitamins build up in your body? - Factual Questions - Straight Dope Message Board](http://boards.straightdope.com/sdmb/showthread.php?t=514857) Suffice it to say, deficiency is far, far more prevalent than previously suspected, supplementation of milk with vitamin D may be preventing rickets, but lots of other deficiency problems are now coming to light (no pun intended), and vitamin D is associated with a LOT more than just bone health these days. And don’t worry about showering, you won’t wash off the vitamin D. ---
**Author:** ![Markxxx](https://avatars.discourse-cdn.com/v4/letter/m/5daacb/32.png) [@Markxxx](https://boards.straightdope.com/u/Markxxx)\ **Post date:** [May 16, 2009, 9:17pm UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/14 "2009-05-16T21:17:47Z")
A lot of vitamin D is made through the eyes as well. The use of sunscreen and sunglasses has reduced a lot of Vitamin D. Of course if people would just eat a bowl of “Total” cereal…🙂 ---
**Author:** ![ToeJam](https://avatars.discourse-cdn.com/v4/letter/t/dfb087/32.png) [@ToeJam](https://boards.straightdope.com/u/ToeJam)\ **Post date:** [May 16, 2009, 9:25pm UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/15 "2009-05-16T21:25:12Z")
Thanks Q. That’s a great article in there from the NEJoM that I’ll definitely have to read! ---
**Author:** ![Broomstick](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/broomstick/32/246_2.png) [@Broomstick](https://boards.straightdope.com/u/Broomstick)\ **Post date:** [May 17, 2009, 3:35am UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/16 "2009-05-17T03:35:49Z")
> [@Markxxx](#): > > A lot of vitamin D is made through the eyes as well. The use of sunscreen and sunglasses has reduced a lot of Vitamin D. On the other hand, sunglasses reduce your chances of getting cataracts. Granted, those are curable these days. Really, it seems obvious to me that people evolved to get most of their vitamin D from sunlight. There should be a happy medium between “sunscreen all the time” and “no sunscreen at all” that allows one to minimize skin cancer while maximizing vitamin D. This would be partly dependent on one’s quantity of skin pigment so a blanket recommendation probably couldn’t be made, but surely there is a way to to come up with a sliding scale. ---
**Author:** ![ToeJam](https://avatars.discourse-cdn.com/v4/letter/t/dfb087/32.png) [@ToeJam](https://boards.straightdope.com/u/ToeJam)\ **Post date:** [May 17, 2009, 3:38am UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/17 "2009-05-17T03:38:39Z")
> [@Ro0sh](#): > > So if you’re supplementing yourself, make sure you’re getting the right form that you need: cholecalciferol. :smack: I just read calcitriol is the active form you need if you’ve got the Vitamin D issues. Give \*\*Calcitriol \*\*and Calcium supplements. My bad. ---
**Author:** ![Khadaji](https://avatars.discourse-cdn.com/v4/letter/k/9e8a1a/32.png) [@Khadaji](https://boards.straightdope.com/u/Khadaji)\ **Post date:** [May 17, 2009, 11:20am UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/18 "2009-05-17T11:20:17Z")
I mention this every time Vitamin D is discussed. My nutritionist told me that at least 40% of the population is D deficient. He recommended I read the book _The Vitamin D Cure_ by James Dowd. I do feel like I have more energy and believe that I have depression less often and it lasts for fewer days. Note though that I tested very low for that and other Vitamins, so in my case the results could be attributed to one of several vitamins. ---
**Author:** ![Alex\_Dubinsky](https://avatars.discourse-cdn.com/v4/letter/a/dbc845/32.png) [@Alex\_Dubinsky](https://boards.straightdope.com/u/Alex_Dubinsky)\ **Post date:** [May 17, 2009, 5:17pm UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/19 "2009-05-17T17:17:45Z")
> [@Furious\_Marmot](#): > > Got a peer-reviewed citation for that? It was taught to me matter-of-fact that Seasonal Affective Disorder was caused by a deficiency in Vitamin D. However, it seems things may not be so clear-cut. > [@Ro0sh](#): > > in that case ordinary Vitamin D wouldn’t help you- you’d need the ACTIVATED form of Vitamin D3, which have a half life if I recall of around 20 days to a month- because if it’s the sunlight that’s an issue that’s a step in the Vitamin D activation, getting the inactive form orally does nothing for you if Sunlight’s the problem. I did not know that! So, typical vitamin D supplements don’t actually do their role of giving you useful vitamin D? Is it possible to buy calcitriol, or is it regulated? ---
**Author:** ![Alex\_Dubinsky](https://avatars.discourse-cdn.com/v4/letter/a/dbc845/32.png) [@Alex\_Dubinsky](https://boards.straightdope.com/u/Alex_Dubinsky)\ **Post date:** [May 17, 2009, 5:32pm UTC](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609/20 "2009-05-17T17:32:39Z")
> [@Ro0sh](#): > > It turns out the [Cited article](http://www.springerlink.com/content/h5q5rb2lpetmf8gn/) ACTUALLY STATES THE opposite. :smack: Here is another study: [Vitamin D May Not Be The Answer To Feeling SAD | ScienceDaily](http://www.sciencedaily.com/releases/2009/03/090317142847.htm) The problems I find with the study I linked (I cannot read the springerlink study) is 1) they measured blood serum, which really doesn’t tell you anything. It’s the level of nutrients in all the tissues that count. For example, hyperthyroidism causes both high blood calcium and osteoporosis (in fact the two obviously go hand-in-hand). In fact it’s a big pet peeve of mine that doctors take blood serum levels to mean something significant (it’s another facet of the ignorance related to nutrition exhibited by modern medicine). 2) the participants were in Shanghai, which is neither a northern city, nor are its residents known for staying indoors. The studies that showed vitamin D supplementation benefited winter depression do not get canceled out by narrow molecular studies that fail to see a link. [Next page](https://boards.straightdope.com/t/sunshine-vitamin-d-and-showering-whats-the-real-deal/496609.md?page=2)