Is Sunscreen a Lifesaver or a Poison? | Hacker News Reader

Is Sunscreen a Lifesaver or a Poison?

fivethirtyeight.com

44 pointsadamzerner61 comments

Since the title is linkbait-y, I'll share that after reading it, I think the article boils down to these two quotes:

"The bottom line is that although there are holes in our knowledge, there is no concrete evidence of any chemical risks of sunscreen at typical doses."

"In the case of melanoma, the more dangerous form of skin cancer, there’s no data that tells us whether sunscreen works."

What we do know is that sunburns are uncomfortable and mess up your skin for a while, so for me choice between getting sunburned or applying sunscreen is clear. If you are not going to get sunburned, sunscreen does not really matter.

Does sunscreen have to be an all or nothing affair? This seems to be, to me, the underlying assumption made on both sides of these arguments.

I live in Southern California and work by the beach. I put sun block on when I know I'm going to be outside a lot and my exposure will be high... Like most people I previously assumed. Not when I'm going to be outside for an hour. I doubt I'm killing myself in either case.

Zinc oxide based sunscreen is totally safe with zero question marks. Just use the white zinc oxide stuff on parts that are likely to burn or get over exposed.

Do you know of any brands that don't get greasy? I've been using Green Beaver, but it stays visible all day long. It's not white, but there's oil.

I use Neutrogena Sensitive Skin Broad Spectrum. Gives the skin a healthy glow. In fact, my sister sometimes uses it as a base for makeup because of this.

Whether or not you consider that "greasy," I don't know. It doesn't feel greasy to me. Give it a shot.

Although containing zinc oxide, that product includes ingredients that I believe the parent post was looking to avoid. In particular, retinyl palmitate [1].

As an aside, the EWG's Skin Deep database is a useful place to find ingredients of potential concern for popular products:

http://www.ewg.org/skindeep/

[1] http://www.ewg.org/skindeep/product/567689/Neutrogena_Sensit...

Aside from cancer, one needs to be concerned about aging: just look at the difference between the sides of truck driver William McElligott's face: http://www.huffingtonpost.ca/2012/06/06/bill-mcelligott-sun-...

The UV frequencies that contribute most to that effect aren't really blocked by the sorts of sunscreen you can buy in the US.

Effective "broad spectrum" sunscreens have been available in the USA for years. Perhaps there's a wider or better variety of UVA-blocking sunscreens outside the USA, but what you can get here is still effective and approved/regulated by the FDA.

> sunscreens will have to prove they provide good protection against both forms of the sun’s dangerous ultraviolet rays to claim they reduce the risk for skin cancer, sunburns and wrinkles ... Only sunscreens that pass a test that shows that they shield skin from both ultraviolet A (UVA) and ultraviolet B (UVB) rays will be allowed to be labeled “broad spectrum”

http://www.washingtonpost.com/national/fda-cracks-down-on-su...

What places have said sorts of sunscreen?

Europe and Japan. You can probably order some Garnier Ombrelle suncreen from Canada that contains Mexoryl. That's the UVA-blocking ingredient that we're missing in the US.

Why is it not in the US?

Because the FDA works in mysterious ways apparently

http://www.wnd.com/2013/03/fda-to-consumers-burn-for-all-we-...

Unfortunately the article doesn't delve into the controversy over sunscreen limiting Vitamin D production, and all of the problems that can cause (thin, weak and/or brittle bones, as well as possible cancer risks: http://www.webmd.com/cancer/news/20111004/low-vitamin-d-leve...)

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.

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

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.

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.

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.

You can't uniformly apply sunscreen on your entire body. Depending on type of skin, vitamin D will hit maximal daily production from sunlight in range of very fast to very slow.

So, yes, sunscreen might block some vitamin D production for some people, or might not do it at all.

Its perhaps prudent to apply it to some skin parts that are most affected by sunlight (face, shoulders) and leave other body parts without it. There you have benefits of both worlds.

Furthermore, vitamin D is not the only substance produced by the skin via sunlight (although we don't know much about other ones), so vitamin D from diet is not a substitute for it. Furthermore, vitamin D from diet can easily cause calcification depending on other factors (vitamin K and A in the diet and genetics) while there is internal protection for body made one.

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.

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.

Isn't that for adults though? My understanding is that kids tend to need much more vitamin d than adults (for growing bones).

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.)

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.

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.

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.

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.

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?

A high percentage of the population is Vitamin D deficient regardless of sunscreen use. The Recommended Daily Intake is way too low. Most people would be better off if they supplemented Vitamin D.

Recent studies have shown that people really should be supplementing 1000-2000 IU, that it has a safe upper limit of ~10,000 IU. The RDI is currently like ~500IU.

Agreed, there are several potential issues that make it difficult to say there's no downside. There's a difference between Vitamin D production and absorption. Have we firmly established that it's better to absorb all via digestion?

Moreover, tanning is due to an immune response. I can't speak to whether that in itself could have positive effects of the immune system, I would like to know more.

While the cons may very well outweigh the pro (ie cancer & skin damage) not sure why the other isn't discussed in context of moderation.

And no one has yet mentioned rickets!

Once virtually eliminated, rickets has increased markedly, in some studies as much as five-fold. In the malls I now occasionally see children who obviously have rickets. Unless corrected early, the adult will bear the scars of the child.

Also there is mention that ingestion of vitamin D is superior to sun exposure but AFAIK there is no evidence of that. The ingestive route has it's own problems.

It's worse than that. There is reasonable evidence that vitamin D deficiency contributes to a number of cancers and that heavy use of sunscreen has a questionable benefit on net mortality rates.

http://www.medpagetoday.com/HematologyOncology/SkinCancer/78...

Tech related aside, the design of sun resistant clothing that doesn't overheat you is an area that is seeing a lot of advancement recently.

Polyester fabrics with texture to keep some air under the fabric and thin merino wool poly blends (that have a bit of natural texture) really seem to work. They can act almost like a mesh that still blocks the sun.

Do you have any example clothing products? I am in search of this sort of active wear.

The patagonia sun shade hoody is my favorite for wearing at high elevation or on the water when there is some wind though it can be too hot if their isn't wind.

For warmer conditions there are some great pieces in their summer trail running line (on clearance at the moment) including the air flow and gamut shirts:

http://www.patagonia.com/us/shop/web-specials-mens-trail-run...

Edit: opt for the stuff with mesh zones, the straight cap 1 stuff doesn't breath as well. Their merino 1 t shirts are also nice.

Also check out fly fishing clothing by them and others for sun protective clothing with a less athletic look.

I've been using this one for a few years now and love it: http://www.rei.com/product/862927/rei-sahara-tech-long-sleev...

SPF 50, tons of pockets, quick dry material, vents in the back and armpits for air circulation. It even has little snappy things to hold your sleeves when you roll them up.

The added benefit of a shirt over sunscreen is that the shirt keeps bugs off too.

Thank you!

Check out Solumbra products - http://www.sunprecautions.com/

I have one of their long sleeve "jackets" that you can wear in the water. Their products are not cheap, but they do last a long time, mine is over 10 years old.

Thank you!

I like the Columbia Omni Shade clothing, for example: http://www.columbia.com/Omni-Shade/Technology_Omni-Shade,def...

It would be interesting to hear more about potential evidence linking sun exposure and sunscreen to malignant melanomas as opposed to basal and squamous cell carcinomas. BCCs and SCCs, while malignant, do not pose the same risks of metastasis as melanoma, so I would be much more inclined to alter my behavior given such evidence.

In general (but not always) I like to assume that balance is the key. Life is carcinogenic, and too much of anything is probably harmful.

I think focusing in on skin cancers and skin aging is myopic. This is what all these analyses do. Yes, sunscreen probably reduces skin cancers and aging from sun exposure. But there is evidence that depriving yourself of sun exposure leads to a higher overall death rate. You dodge melanoma but increase risk of a heart attack or various internal cancers. People who work outside live longer, despite looking "weathered" in their old age.

Sun screen doesn't block sun exposure though. It screens it. You're still getting sun exposure, just not amounts that are going to burn you.

It is known that cyclic aromatic compounds (like sterols) can pass through the cell membrane layer. It is also known that cyclic aromatic compounds can bind DNA (this is how steroid hormones work). It is also known that DNA breakage can occur when ionizing radiation strikes alkylating agents intercalcated with the DNA backbone.

Honestly, it wouldn't surprise me if sunscreen has sterol-derived compounds that in the presence of ionizing radiation could cause skin damage. We hear about this stuff all the time in things like cigarette smoke, charred meat, etc. etc.

That being said, the article doesn't address the incidence of cancer caused by NOT using sunscreen. Similarly, not all vaccinations are not 100% safe, but the risk you take from not having the vaccination is far greater if you didn't take it. Therefore, people will get scared off from using sunscreen from articles like this, likely increasing the incidence of skin cancer.

Am I the only one troubled by a statement like this:

"As to whether I should be slathering my kid with sunscreen or not, the good news is that I’m not causing any damage by doing so."

At the end of an article that otherwise claims to investigate the scientific merit of the case against sunscreen?

It's fine if you want to say "I'm very likely not causing damage ..." But it seems awfully unscientific to claim that the good is that I'm not causing ANY damage by doing so.

Also, I feel like this is an endemic thought process in our post-modern society. Humans want answers. Humans like answers. Scientific logic produces very few slam-dunk answers. So while we all trot around claiming to be "scientific" in our outlook, we rarely if ever apply truly scientific thought to our daily routines. Not that it's easy to do, but it's frustrating when people mis-associate belief with knowledge.

I'm super white, and I barely wear sunscreen. I put some on the other day for a 4hr river float.. But I spent a full day fishing the river yesterday; in direct sun, no sunscreen in 90 degree heat and I'm only mildly burned.

I remember burning a lot worse when I was a teenager.. But I think it had something to do with drinking Mt. Dew all the time. I've pretty much entirely removed high fructose corn syrup from my diet. I eat fruit for my sugar fix more often these days. I also supplement vitamin-d now, perhaps that also has something to do with it? This is all just anecdotal, but perhaps if you burn quickly and easily you should take a look at your diet.

I thought this was a little weird: "melanoma diagnosis increased by 1.9 percent annually between 2000 and 2009."

I would have thought that this would have went down through this period. I was born in 1973 and wore some sunscreen as a kid and I would assume the amount of sunscreen wearing has increased over time and sun exposure has decreased. Some time before that people were barely wearing sunscreen or limiting exposure so as they die out I would expect the melanoma rate to decrease.

Of course there would be a lot of compounding factors, like longer lifespans, a higher percentage of Americans living in the South, etc. Just seems a little odd.

The reason melanoma incidence is increasing is because of a "diagnostic drift," similar to what we see in the rise of psychological disorders: http://www.ncbi.nlm.nih.gov/pubmed/19519827

We are more routinely getting skin lesion check ups and dermatologists and oncologists are more and more cautious, leading to an ever-increasing incidence of stage I melanoma. However, we're not really seeing an increase in later stage melanoma, meaning that the "true" incidence of melanoma is not increasing.

It's sort of a huge public health scam. The dermatologists are using this vanity metric of increased diagnoses as evidence that we're in the middle of a melanoma/skin-cancer epidemic, when it's simply not the case. Not that safe sun exposure practices shouldn't be promoted, but the motor behind these messages is a bit of a scam.

Don't forget that we have baby boomers entering the middle/later stages of life, where we would expect such diagnoses to be made. I'd expect the death rate in the US to steadily increase with respect to population over the next couple decades, then gradually decline.

I wear sunscreen so I don't get a burn. I'm not a particularly fair-skinned person but a day out on a boat will burn me to a crisp.

Also helps keep the freckles and moles down.

Nice example of Betteridge's law[0] here. While as a biologist, I am supremely aware that plausible biological mechanism alone shouldn't be sufficient to drive public policy, UV induced DNA damage causing melanoma is one of the better understood mechanisms for oncogenesis. The real question to me is not whether sunscreen works at preventing UV damage, and thus skin cancer, but to what extent acute, high dose UV exposure, especially at a young age, can do to lifetime cancer risk. If it is the case that one or two bad sunburns can dramatically increase risk of skin cancer, it will be very difficult to design a randomized clinical trial to demonstrate the effectiveness of sunscreen in adults. [0]: http://en.wikipedia.org/wiki/Betteridge's_law_of_headlines

It's worth noting that sunscreen in countries other than the US does more to prevent skin cancer, so the balance might be different in different places.