6 ms·

Except that all evidence points to the fact that sunscreen/sunblock usage doesn't have an effect on vitamin D intake through sun exposure. People that use it t

Except that all evidence points to the fact that sunscreen/sunblock usage doesn't have an effect on vitamin D intake through sun exposure. People that use it tend to spend more time in the sun than those that don't. Also, vitamin D is more effective through ingestion as opposed to sun exposure anyway.

_delirium 12y ago
The amount of sun exposure needed to max out skin-produced vitamin D in sunny regions during the summer (which is where/when most people would use sunscreen) is very low anyway. Somewhere around 30 minutes of exposure per week does it. People usually put on sunscreen when intending to be out in the sun for hours, and there is definitely no need to have hours of exposure to summer sun from the perspective of Vitamin D production.
- jobu 12y ago
  Isn't that for adults though? My understanding is that kids tend to need much more vitamin d than adults (for growing bones).
  - _delirium 12y ago
    It's not really how much you need in terms of a volume, but just how long it takes to get to maximum blood concentrations. In direct sunlight in the summer you get to maximum concentrations very quickly, like <15 minutes timescale. And staying out in the sun longer doesn't raise levels further. So if you just semi-regularly get 30 minutes of sun (possibly less), the blood concentration will stay maxed out. (In other words, some sun every day or two might help, but 8 hours of exposure on one day does no more good than much less exposure would.)
    - purephase 12y ago
      You said exactly what I was trying to point out. I wouldn't put sunblock on my daughter or myself for <20min exposure. That just seems extreme. When I apply it, we're heading out for hours, or all day. This also doesn't account for skin variances. We're extremely fair-skinned and burn easily. There is no way, even through clothing coverage, I would risk the possible burns that I've seen other children have.
bcebulla 12y ago
That's not true. In the controlled setting, sunscreen affects ability of skin to make vitamin D, by about half: http://www.ncbi.nlm.nih.gov/pubmed/22512875 http://www.ncbi.nlm.nih.gov/pubmed/22512875 Sunbathers who use sunscreen tend to not have lower vitamin D levels than non-sunbathers who don't use sunscreen, because, well, people who don't use sunscreen don't get sun exposure anyhow. Also, when the human genome was evolving, sun exposure accounted for 90%+ of all vitamin D intake, diet accounted for less than 10%. We know this by looking at the diets and vitamin D levels of hunter gatherers.
- purephase 12y ago
  You're referring to a study that used 37 volunteers that were exposed for 20 min. When I apply sunblock to me or my daughter, it's because we're going to be outside for well over 20 minutes. For that length of time, depending on conditions, I probably wouldn't even bother. My point stands, if you apply sunblock intending to spend 1+ hour(s) in the sun, then you'll likely benefit from the vitamin D exposure.
  - bcebulla 12y ago
    In a controlled setting, sunblock will always affect vitamin D production, whether you expose for 20 minutes or 60 minutes or 120 minutes, or whether you test 37 subjects or 370 subjects. The reason is that 7-dehydrocholesterol is photolyzed by UV light in the 280-320nm range (mostly UVB) to previtamin D. Sunblock works to absorb UVB (and usually UVA) to prevent it from penetrating your skin. Thus sunblock limits the amount of UVB penetrating your skin, and limits your ability to make vitamin D. That being said, yes, you will still make some vitamin D with sunblock on because sunblock is not perfect at absorbing UVB. Just not as much as you would without.
    - purephase 12y ago
      None of that changes the fact that increased exposure to UV will have net-positive benefits in regards to vitamin D intake. If you apply sunblock you just have to spend more time outside in order to absorb more vitamin D via UV.
facepalm 12y ago
Any links to the result that suncreen usage doesn't affect Vitamin D production? (Intake seems the wrong word)? It's the first time I heard that.
- purephase 12y ago
  I should clarify that statement. Evidence points to the fact that it does reduce vitamin D production, but it does not stop it entirely. If you apply and then spend a lot of time in the sun, your vitamin production will be decreased, but not entirely. People who routinely apply sunblock spend more time in the sun, so they will end-up producing more than those who spend no time in the sun at all. It's the cost of weighing burns against vitamin D production. The skin cancer worry (legitimate) due to sun damage vs. decreased vitamin D production is probably a good bet to make.
  - JoeAltmaier 12y ago
    I guess it depends on the ratio. Does sunscreen suppress D production more or less than it reduces harmful radiation? Or are they the same thing? Sunscreen is for one thing - so you can spend more time in the sun. If you'd burn after 15 minutes, then SPF 20 means you can spend about 5 hours with sunscreen. No SPF will entirely eliminate the sun - that'd be SPF infinity, right? SPF is a ratio.
  - facepalm 12y ago
    Too bad that the 503 article didn't mention Vitamin D at all. Where exactly is the sweet spot? Leaving sun screen aside (as that seems to only prolong the time you need to stay in the sun for an effect, good or negative). I suspect the number of minutes you should stay in the sun per day is > 0. But how high is it?

_delirium 12y ago

The amount of sun exposure needed to max out skin-produced vitamin D in sunny regions during the summer (which is where/when most people would use sunscreen) is very low anyway. Somewhere around 30 minutes of exposure per week does it. People usually put on sunscreen when intending to be out in the sun for hours, and there is definitely no need to have hours of exposure to summer sun from the perspective of Vitamin D production.

jobu 12y ago
Isn't that for adults though? My understanding is that kids tend to need much more vitamin d than adults (for growing bones).
- _delirium 12y ago
  It's not really how much you need in terms of a volume, but just how long it takes to get to maximum blood concentrations. In direct sunlight in the summer you get to maximum concentrations very quickly, like <15 minutes timescale. And staying out in the sun longer doesn't raise levels further. So if you just semi-regularly get 30 minutes of sun (possibly less), the blood concentration will stay maxed out. (In other words, some sun every day or two might help, but 8 hours of exposure on one day does no more good than much less exposure would.)
  - purephase 12y ago
    You said exactly what I was trying to point out. I wouldn't put sunblock on my daughter or myself for <20min exposure. That just seems extreme. When I apply it, we're heading out for hours, or all day. This also doesn't account for skin variances. We're extremely fair-skinned and burn easily. There is no way, even through clothing coverage, I would risk the possible burns that I've seen other children have.

bcebulla 12y ago

That's not true. In the controlled setting, sunscreen affects ability of skin to make vitamin D, by about half: http://www.ncbi.nlm.nih.gov/pubmed/22512875 http://www.ncbi.nlm.nih.gov/pubmed/22512875 Sunbathers who use sunscreen tend to not have lower vitamin D levels than non-sunbathers who don't use sunscreen, because, well, people who don't use sunscreen don't get sun exposure anyhow. Also, when the human genome was evolving, sun exposure accounted for 90%+ of all vitamin D intake, diet accounted for less than 10%. We know this by looking at the diets and vitamin D levels of hunter gatherers.

purephase 12y ago
You're referring to a study that used 37 volunteers that were exposed for 20 min. When I apply sunblock to me or my daughter, it's because we're going to be outside for well over 20 minutes. For that length of time, depending on conditions, I probably wouldn't even bother. My point stands, if you apply sunblock intending to spend 1+ hour(s) in the sun, then you'll likely benefit from the vitamin D exposure.
- bcebulla 12y ago
  In a controlled setting, sunblock will always affect vitamin D production, whether you expose for 20 minutes or 60 minutes or 120 minutes, or whether you test 37 subjects or 370 subjects. The reason is that 7-dehydrocholesterol is photolyzed by UV light in the 280-320nm range (mostly UVB) to previtamin D. Sunblock works to absorb UVB (and usually UVA) to prevent it from penetrating your skin. Thus sunblock limits the amount of UVB penetrating your skin, and limits your ability to make vitamin D. That being said, yes, you will still make some vitamin D with sunblock on because sunblock is not perfect at absorbing UVB. Just not as much as you would without.
  - purephase 12y ago
    None of that changes the fact that increased exposure to UV will have net-positive benefits in regards to vitamin D intake. If you apply sunblock you just have to spend more time outside in order to absorb more vitamin D via UV.

facepalm 12y ago

Any links to the result that suncreen usage doesn't affect Vitamin D production? (Intake seems the wrong word)? It's the first time I heard that.

purephase 12y ago
I should clarify that statement. Evidence points to the fact that it does reduce vitamin D production, but it does not stop it entirely. If you apply and then spend a lot of time in the sun, your vitamin production will be decreased, but not entirely. People who routinely apply sunblock spend more time in the sun, so they will end-up producing more than those who spend no time in the sun at all. It's the cost of weighing burns against vitamin D production. The skin cancer worry (legitimate) due to sun damage vs. decreased vitamin D production is probably a good bet to make.
- JoeAltmaier 12y ago
  I guess it depends on the ratio. Does sunscreen suppress D production more or less than it reduces harmful radiation? Or are they the same thing? Sunscreen is for one thing - so you can spend more time in the sun. If you'd burn after 15 minutes, then SPF 20 means you can spend about 5 hours with sunscreen. No SPF will entirely eliminate the sun - that'd be SPF infinity, right? SPF is a ratio.
- facepalm 12y ago
  Too bad that the 503 article didn't mention Vitamin D at all. Where exactly is the sweet spot? Leaving sun screen aside (as that seems to only prolong the time you need to stay in the sun for an effect, good or negative). I suspect the number of minutes you should stay in the sun per day is > 0. But how high is it?