It seems that everyone knows the figure of upto 10,000 units of Vitamin D from 20 minutes full body sun exposure for a pale skinned person. After a time more Vitamin D is not made despite further sun exposure as the process is regulated preventing toxicity developing.
My real question is this. How long does the prevention of more vitamin D being made last for?
Do you make another 10,000 units of Vitamin D if you spend 20 minutes in the sun the next day? Or does the inhibition last for two or three days after sun exposure. If this was the case you could only make 10,000 twice per week or an average of about 3000 units per day.
I have not been able to find any information on how Vitamin D production is regulated in the skin but it seems like it should be an interesting question to ask.
asked byMatt_1 (19245)
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on January 15, 2011
at 10:44 PM
I had looked at it a while back. The 10,000 units comes from a study. It's really between 10k and 25k units (lot of variables like location, skin color, etc). Basic idea is that Ultra Violet B (UVB) interacts with a type of cholesterol in the skin to create Vitamin D precursors. Those precursors convert to Vitamin D in the body over time (I think it was something like 8 hours, although don't quote me on that).
The precursors are "self regulating" because they're destroyed by UVB. When they get up to X concentration, they're destroyed as fast as they're created. That's why there's no toxicity, and it would be per day for the most part.
on October 29, 2011
at 05:13 PM
Hope you feel better. What I found to raise Vit D levels fast is Carlson's Cod Liver Oil...my blood levels went way up. I used to take it daily now 2-3 times a week. Raising Vit D has helped immensely with chronic health concerns. Also, I went to Disney and Universal in April and walked and walked in the bright sunshine for a week. Since then my health problems (multiple food sensitivities, mild migraine, fatigue, depressed affect) have improved even more! Hey...now I have an excuse for some traveling to a warm sunny environment. Isn't it common sense that the closer we get to eating and living well the better we feel? Best wishes.
on April 29, 2011
at 08:41 PM
Thanks Todd, very interesting! I am printing that out to put with some other articles I have gathered.
I think that most likely the reason I have felt so much better since I started the supplementation, is that my levels were so very low. I had a level of only 11. Those people in the study had levels of 50 or so, which is already a healthy level (so most likely their depression not related to Vitamin D deficiency, so would not see an improvement).
I have never been termed "clinically" depressed. I've just felt a certain way I can't really describe - that I have known is not normal. I think in my own personal case, mine could easily be related to simply not getting sunlight (despite living in Tucson, if you are covered in sunlblock and clothes you are not getting sunlight), and subsequently, not getting Vitamin D.
I am very anxious to be tested again to see if I have in fact raised my levels. I never went into this thinking my mood would change. I was just desperately trying to raise my white blood count.
I have noticed when I do my five minutes in the sun...that I get a bit of an almost euphoric feeling after about three minutes. It is almost the same feeling I will get from a cup of coffee (which for me is a good feeling). I know I am not imagining it. I actually feel it. I do not get that if I am covered in block. Just spent 5 days at Disney World in the sun, covered, and never felt "euphoric" in that sense (not counting the fun of Disney, you know what I mean).
You guys are great to help me like this, and much appreciated! The more literature I can gather, the better. I tend to over-analyze anything health related as I fear making a mistake. However, regarding the Vitamin D - my doctor put me on that before I ever read a thing on it. Soon as my results came back.
- Annie xoxo
on April 29, 2011
at 04:29 PM
Today's post on Ev Psych touches a little on your question. Here's a link
on April 28, 2011
at 10:51 PM
Thank you UncleLongHair. I have been taking 5,000 iu of D3 now for 6 weeks, and will be going in for a D test in 6 more weeks. I cannot even begin to tell you how much better I feel since i started taking the supplements. Prior to that I was getting 400 from my multi, and the rest from food, fish and fish oils, etc. I was getting a lot, but not enough to make up for a severe deficiency.
I wanted to try obtaining some from the sun as well, so am just not sure on the timing.
I went to the doctor to have blood tests taken and my Vit D level was very low as well as my white blood counts were off the charts low. I went in due to feeling very sluggish. Once I started on the D, within a week or two, my mood and kind of depressive feelings started to subside (was taking 10,000 iu at that time), and my energy started to slowly come back. So I do know my body is processing and absorbing the supplements.
I am to go back to check my D levels as well as my white blood count levels, so I am hoping they have both increased.
Thank you so much for taking the time to answer my question. I really appreciate it.
on April 28, 2011
at 09:46 PM
I did some reading on this a while back. Opinions of course vary, though I remember reading one estimate that suggested that the recommended daily dose of Vitamin D can be obtained via one hour of sun exposure with 50% of your skin exposed, without sunscreen, at the equator.
Without bothering to calculate that too precisely, suffice it to say that your typical North American / European / office worker probably gets a tiny fraction of that exposure, maybe 1/100 or 1/1000, considering the lack of being outdoors, use of sunscreen, and general fear of the sun in our culture.
There aren't many sources of vitamin D in food, primarily certain fish, dairy and enriched processed foods. Most people on a paleo diet would avoid all of those but the fish, and would probably have to put in substantial effort to eat enough fish to get their vitamin D requirement. I think everyone on a paleo diet should consider their vitamin D intake and go out of their way to make sure they have enough.
Vitamin D is a very important nutrient and is also a hormone, and lack of it can cause lots of issues including muscle soreness, moodiness, and other health problems. When I was trying to increase my running distance last year, I had a lot of muscle soreness and joint pain, and starting a Vitamin D supplement completely eliminated the symptonms within about a week, so I suspect that I was deficient (though I never got tested).
That said, I would also be cautious about getting a lot of vitamin D in capsule form, since synthetic vitamin D may be absorbed differently. The best place to get all vitamins is from food. If that isn't possible, then it should be from minimally processed supplements derived from food, for example certain fish oils or high vitamin butter oils.
on April 28, 2011
at 09:06 PM
I have a question about getting very little amounts of Vit D at a time. I live in Tucson, so the rays are strong for a good portion of the year. I am VERY fair skinned, 47 years old, and very bad sun damaged skin from many years ago. Have worn block 365 days a year now for 20 years.
I have been venturing just 5 minutes a day, three times a week. I am pink after those five minutes and I cannot continue this!
Do you think just 1-2 minutes, through the day, totaling op to 5-6 minutes, would give the same D benefit as all at once? Or does it perhaps take a couple minutes before you even start benefitting? Would they be wasted minutes?
I keep hearing that just a few minutes a day will not hurt you, but for those of us with very fair skin, it makes a difference.
Thanks for any opinions on this. I appreciate your help.
on January 16, 2011
at 06:12 PM
I would guess each person has a set limit that the body likes to maintain. The limit is probably also affected by other variables like diet. If you are already close to the limit, then the next time you go out in the sun, your body will not make much D as it will only take a short while and a little bit of D to reach your max levels again.