# Vitamin D questions **URL:** \ **Category:** Factual Questions\ **Created:** [July 13, 2009, 11:20am UTC](https://boards.straightdope.com/t/vitamin-d-questions/502848 "2009-07-13T11:20:04Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![Khadaji](https://avatars.discourse-cdn.com/v4/letter/k/9e8a1a/32.png) [@Khadaji](https://boards.straightdope.com/u/Khadaji)\ **Post date:** [July 13, 2009, 11:20am UTC](https://boards.straightdope.com/t/vitamin-d-questions/502848/1 "2009-07-13T11:20:04Z")
I know that Vitamin D is created in the body with exposure to the sun, but I had some questions: [ol] [li]Does it matter if I take in morning sun or afternoon (when the sun is higher in the sky?)[/li][li]Does it matter if I take in summer sun rather than winter sun? I mean, if I need 15 minutes of exposure in the summer, do I need 30 in winter (if I were crazy enough to expose the same amount of skin in both types of weather.)[/li][li]Does glass block the effects? I mean, can I sit sitting room in front of the big glass window and get the same benefit of stepping outside for the same amount of time?[/li][li]Do any man-made lights help create Vitamin D? I mean, which types of rays are needed?[/li][li]How do the animals get theirs? I assume fur does not help, as it blocks the sun’s rays.[/li][/ol] ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [July 13, 2009, 1:08pm UTC](https://boards.straightdope.com/t/vitamin-d-questions/502848/2 "2009-07-13T13:08:12Z")
Unless you have ricketts, you really don’t need to worry about it. You just need a little bit of sunlight to get what you need. It’s not really something you need to extensively plan out. ---
**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:** [July 13, 2009, 1:29pm UTC](https://boards.straightdope.com/t/vitamin-d-questions/502848/3 "2009-07-13T13:29:14Z")
> [@Smeghead](#): > > Unless you have ricketts, you really don’t need to worry about it. You just need a little bit of sunlight to get what you need. It’s not really something you need to extensively plan out. Untrue, sadly. Vitamin D deficiency is now being recognized as a significant problem in the US and other places. I don’t have the full info at my fingertips, but briefly: Exposure of arms and legs for 5 to 30 minutes (depending on time of day, season, latitude, and skin pigmentation) between the hours of 10 a.m. and 3 p.m. twice a week is often adequate. Exposure to one Minimal Erythemal Dose (the least amount of UV exposure that results in pigmentation without sunburn) while wearing only a bathing suit is equivalent to ingestion of approximately 20,000 IU of vitamin D. ---
**Author:** ![Khadaji](https://avatars.discourse-cdn.com/v4/letter/k/9e8a1a/32.png) [@Khadaji](https://boards.straightdope.com/u/Khadaji)\ **Post date:** [July 13, 2009, 1:29pm UTC](https://boards.straightdope.com/t/vitamin-d-questions/502848/4 "2009-07-13T13:29:54Z")
> [@Smeghead](#): > > Unless you have ricketts, you really don’t need to worry about it. You just need a little bit of sunlight to get what you need. It’s not really something you need to extensively plan out. My apologies, I’m grumpy and every time I phrase this is sound snarky, but - I was asking for \*information \*and not advice. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [July 13, 2009, 2:24pm UTC](https://boards.straightdope.com/t/vitamin-d-questions/502848/5 "2009-07-13T14:24:08Z")
> [@Khadaji](#): > > Do any man-made lights help create Vitamin D? I mean, which types of rays are needed? Light absorption by vitamin D precursors is [greatest at 260 to 290 nm.](http://www.photobiology.com/photobiology99/contrib/olga/index.htm) That’s in the [UVB](http://dermatology.about.com/od/glossaryu/g/uvb.htm) range; the same stuff that’ll give you a sunburn. Any lamp that puts out light at those wavelengths will also stimulate vitamin D production. If the lamps are as bright as the sun in the UV, you can use them as sun substitutes, but most lamps are not that bright. ---
**Author:** ![Khadaji](https://avatars.discourse-cdn.com/v4/letter/k/9e8a1a/32.png) [@Khadaji](https://boards.straightdope.com/u/Khadaji)\ **Post date:** [July 13, 2009, 2:47pm UTC](https://boards.straightdope.com/t/vitamin-d-questions/502848/6 "2009-07-13T14:47:46Z")
> [@Qadgop\_the\_Mercotan](#): > > Untrue, sadly. Vitamin D deficiency is now being recognized as a significant problem in the US and other places. > > I don’t have the full info at my fingertips, but briefly: > > Exposure of arms and legs for 5 to 30 minutes (depending on time of day, season, latitude, and skin pigmentation) between the hours of 10 a.m. and 3 p.m. twice a week is often adequate. > > Exposure to one Minimal Erythemal Dose (the least amount of UV exposure that results in pigmentation without sunburn) while wearing only a bathing suit is equivalent to ingestion of approximately 20,000 IU of vitamin D. I was diagnosed with vitamin D deficiency - from a blood test, not just observation - and was put on a MEGA dose for a while, then an over-the-counter large dose daily. This worked GREAT for about a few months. Then I started seeing the same old symptoms, mostly fatique. Some reading suggests that vitamin D, once opened, does not store well. This makes sense, I tend to buy large bottles, so the D may no longer be viable. I started sitting outside in just shorts for 20 minutes each day for few days and I’m back to feeling pretty darn good today. This is the first day I can remember in a few months where I don’t feel like I need a nap (yet.) I can continue to do this for the rest of the summer and for much of the fall - but when winter comes I need to find a viable way to get my vitamin D that doesn’t have a shelf-life. I’m going to chat with my doc about it when I see him again, but I hate to make an appointment for just this - when it is clear that I can get it naturally. Come winter I’m wondering if a full-sprectum lamp will work, or if I can sit down in my sitting room, which gets plenty of sun - but through a window. But I also wondered about animals. I don’t have one, don’t need to know, it just seems interesting. ---
**Author:** ![elfkin477](https://avatars.discourse-cdn.com/v4/letter/e/a9a28c/32.png) [@elfkin477](https://boards.straightdope.com/u/elfkin477)\ **Post date:** [July 13, 2009, 3:47pm UTC](https://boards.straightdope.com/t/vitamin-d-questions/502848/7 "2009-07-13T15:47:34Z")
> [@Smeghead](#): > > Unless you have ricketts, you really don’t need to worry about it. You just need a little bit of sunlight to get what you need. It’s not really something you need to extensively plan out. Untrue for people in many areas. My mom’s being treated for vitamin D deficiency right now and according to the literature she was sent home with people this far north generally have 1/2 the normal level people are expected to have (and mom’s level is less than 1/2 of that!). ---
**Author:** ![DrDeth](https://avatars.discourse-cdn.com/v4/letter/d/b487fb/32.png) [@DrDeth](https://boards.straightdope.com/u/DrDeth)\ **Post date:** [July 13, 2009, 3:48pm UTC](https://boards.straightdope.com/t/vitamin-d-questions/502848/8 "2009-07-13T15:48:43Z")
> [@Khadaji](#): > > Come winter I’m wondering if a full-sprectum lamp will work, or if I can sit down in my sitting room, which gets plenty of sun - but through a window. Doubtful. A full-spectrum light does not emit significant UV, it’s not a sun-lamp. And windows block most UV: > **[Can you tan through glass?](https://www.straightdope.com/21341334/can-you-tan-through-glass)** But I suppose that several hours through glass may suffice, you’d need like 200-300 minutes! Note that after 20 minutes or so of direct full sunlight, human skin stops producing Vit D, it is practically impossible to get too much Vit D from sunlight. OP, how dark is your skin? > **[Vitamin D](https://en.wikipedia.org/wiki/Vitamin_D)** > > Vitamin D is a group of structurally related, fat-soluble compounds responsible for increasing intestinal absorption of calcium and phosphate, along with numerous other biological functions. In humans, the most important compounds within this group are vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol). > Unlike the other twelve vitamins, vitamin D is only conditionally essential in the diet, as with adequate skin exposure to the ultraviolet B (UVB) radiation component of sunlight th... _A critical determinant of vitamin D3 production in the skin is the presence and concentration of melanin. Melanin functions as a light filter in the skin, and therefore the concentration of melanin in the skin is related to the ability of UVB light to penetrate the epidermal strata and reach the 7-dehydrocholesterol-containing stratum basale and stratum spinosum. Under normal circumstances, ample quantities of 7-dehydrocholesterol (about 25-50 µg/cm² of skin) are available in the stratum spinosum and stratum basale of the skin to meet the body’s vitamin D requirements,[12] and melanin content does not alter the amount of vitamin D that can be produced.[19] Thus, individuals with higher skin melanin content will simply require more time in sunlight to produce the same amount of vitamin D as individuals with lower melanin content._ \*\*Qadgop the Mercotan \*\* is correct as usual. Americans now have a much greater problem with too little Vit D. Not enough sunlight, fish or fortified dairy. "The practical reality is that on average, the U.S. diet provides 100 IU/day. " and dudes need _at least_ 200mg, 400mg is the guideline for an average person. ---
**Author:** ![Khadaji](https://avatars.discourse-cdn.com/v4/letter/k/9e8a1a/32.png) [@Khadaji](https://boards.straightdope.com/u/Khadaji)\ **Post date:** [July 13, 2009, 4:01pm UTC](https://boards.straightdope.com/t/vitamin-d-questions/502848/9 "2009-07-13T16:01:20Z")
I am light skinned. My profile’s pic gives an fair representation. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [July 13, 2009, 4:09pm UTC](https://boards.straightdope.com/t/vitamin-d-questions/502848/10 "2009-07-13T16:09:09Z")
> [@Khadaji](#): > > My apologies, I’m grumpy and every time I phrase this is sound snarky, but - I was asking for \*information \*and not advice. Yes, I was a little out of line. My apologies right back at you.