Can people get saturated with vitamin D from sunshine?

[lljkk]

Sunny weather got me wondering...

Is it possible to reach a limit where your body can store no more, at least not from sunshine sources (I presume no limit with pills).

[ChablisTyrant]

No:
"Excessive exposure to sunlight poses no risk in vitamin D toxicity through overproduction of vitamin D precursor, cholecalciferol, regulating vitamin D production. During ultraviolet exposure, the concentration of vitamin D precursors produced in the skin reach an equilibrium, and any further vitamin D that is produced is degraded."

[lljkk]

ah, that means the answer is YES, if the precursors reach an equilibrium.

(Sorry if I made it sound like I was asking about toxicity)

I was thinking that if you rely on sunshine for Vitamin D, what if there were days when you may as well not bother because (probably) already at saturation levels.

[Katymac]

But doesn't that have to be a shed load of Vitamin D more than would be normal in this country?

[lljkk]

I think, from what I'm reading, that there's an X amount of time exposed to vitamin-D making rays, that I want to get daily. The key is daily exposure for X time, to keep stores increasing. What I really wanted to know was whether the overall stores could reach a maximum saturation, but (I think from above & what else I've read) it's more like the ability to add more to the stores reaches saturation after X minutes exposure. So the key is to aim for exposure at least once a day for X minutes solid, and this will lead to long-term increases in body stores.

At my skin tone (medium-darker caucaisan) X = maximum 30 minutes. So for now, that's my target on days with some sun in them. Preferably near noon but possibly ok in the window 9am-5pm in high summer.

Most of us barely get outside, much less near noon, and then the weather doesn't deliver sun every day, so I guess it's hard to say whether there's enough sun in UK or not, and the temps not conducive to exposing much skin, so much is lifestyle dependent in that calculation.

[SweetCharityBeginsAtHome]

Bear in mind it's not just vitamin D, it's nitric oxide production as well. And the protection that tanning adds against melanoma may be relevant depending on your lifestyle.

[Katymac]

I thought I read that apart from high summer that to get enough Vit D you'd have to run around pretty much naked for a couple of hours & that it was torso exposure that was important and that in the UK estimates of how much you need is dramatically under estimated

But typically I can't find where I read it

Which proves the internet is a pain for research!! at least for me

[snice]

I'm sure I read in a magazine (?poss Good Housekeeping at my mum's) that if you live north of a bout Birmingham the chance s of getting enough vit D from sunshine alone are practically nil unless you work outside in all weathers

[SweetCharityBeginsAtHome]

Nobody really knows what "enough" is. We know what's enough to prevent rickets, which is where the usual quotes of "twenty minutes in a short sleeve top" or whatever come from. But we don't know what the optimum amount for general health is.

[downgraded]

So given that most people don't get rickets, most people must get enough?

[MrsLeighHalfpenny]

I assume there's vit D added to food. But I'm just guesing.

[lljkk]

Seems like Lots of confusing information based on back-of-envelope calculations when there is much uncertainty.

This says that 55%+ of caucasian Scottish women are not VitD deficient, even though sunlight is their main source (and modern lifestyles don't encourage outdoor time with much skin exposed). So the hype about being nuddy for 2 hrs a day or outdoors in all weathers if north of Brum look like terrible exaggeration to me.

[SweetCharityBeginsAtHome]

The level to prevent rickets is pretty low. The level to minimise the risk of various cancers, and MS, and heart disease is probably a lot higher. Nobody knows for sure yet,

[SweetCharityBeginsAtHome]

Vitamin D is added to margarine and breakfast cereals.

[Katymac]

& rickets is on the rise in inner cities not just in ethnic/darker skinned populations

They don't test for vitamin D as a matter of course despite potential symptoms; my GP had to get 'special permission' of the practise manage to test me (I am very low)

The adult version of rickets, osteomalacia, is (allegedly) almost never looked for never mind diagnosed & a fair proportion of Vitamin D deficiency is (allegedly) found in people with other diagnoses (often years later)

[HaleMary]

Not entirely on topic, but I spent a year living in a country where summer temperatures were often well over 40 degrees and so humid it was difficult to be outdoors at all. I set a timer and sat out on the balcony for 30 minutes a day in full sunlight all summer - conscious of Vit D issues - but discovered I had Vit D deficiency when I got back to the UK when my GP ran tests because I felt so off.

[Katymac]

Sorry Iljkk am I reading the same article as you I saw that " In winter, just 9.5% of the Caucasian English women were deficient, but that number rose to 40.6% in Scottish women and 64.5% in Asian women"

Which yes I suppose 59.4% weren't deficient........but the comparison with women in the south surely implies a massive difference especially if allowing for increased dietary vit D of the scottish women?

[meglet]

I hope not. I would have OD'd by now.

[lljkk]

59.4% is not "practically nil" though, is it?
And there's no mention of people spending 2 hours/day nude in that article.
Bit like when BBC declared that 'a few yrs' = 41 yrs, I guess.

I was only interested in the science part of saturation, so I may not post on thread again.

[Katymac]

Well I think mathematically 4 times more deficiency despite a food intake increase is a significant difference in sun created Vitamin D

Sorry this isn't what you intended for your thread

[snice]

Sorry OP I have clearly spoiled your thread with my unscientificky nonsense

I think I was guilty of exaggeration when I used the term 'practically nil' but I think its interesting that in the northern parts of the UK many people are Vit D deficient

[lljkk]

Sorry, I didn't mean to sound stroppy. Just, urk, I wanted to try to discuss more of certain-ish science than the uncertain speculation.

Thread has been helpful to me in understanding that small daily exposure is better than a binge once a week, at least.

The mention of nitric oxide in skin is really interesting, although the impacts of that are so mixed in the body, I'm not sure if it merely adds to the confusion. Ditto the research on blood pressure or heart disease impacts.

[MyFriendsCallMeOh]

We live in a southern USA state with permanently sunny weather and blue skies. My dh plays golf and swims outside a lot and is vit d deficient, it's pretty difficult to get all your vit d through sunlight. He takes supplements and drinks milk too on the advice of his doctor, I think you need calcium to aid vit d absorption?

[snice]

I don't think you were stroppy-you were being science-y and I was being chatty. This is why topics are good=I should have seen Geeky and moderated accordingly

[ChablisTyrant]

The Pennines divide in the incidence of inflammatory/autoimmune conditions is interesting. The west of our country gets more cloud cover and so less vit D.

[Gozogozo]

The thing about via d deficiency is that different countries define deficiency at different points. Also UK deficiency points have moved up & up and there are many experts who reckon we need a lot more than the current RDA to avoid deficiency. Equally it is unclear at what level bit D becomes toxic. There is a wide range and the expectation is that deficiency min level & therefore RDA will go up a fair way.