First off, Happy Canada Day to my fellow Canadians!
Our national holiday marks the unofficial start to our all-too-brief summer season and what is more quintessential Canadian summer than rushing outside to soak up some rays?
But before you run off to the beach or up to the cottage, you mustn’t forget about protecting yourself from the sun, right? I mean, that’s the message we’ve had drilled into our collective psyches over the past 30 years, often through the use of creative ad campaigns.
Take Australia’s sun protection message that began in 1981: Slip-Slop-Slap. This campaign, which counsels people to “slip on a shirt, slop on sunscreen, and slap on a hat”, has been heralded as both ingenious and necessary, given that Australia has one of the highest rates of skin cancer in the world.
Clearly, governments around the world have decided there’s tremendous value in promoting the message: too much sun exposure = skin cancer.
Given how diligent we, as Canadians, seem to be about applying sun screen before any outdoor activities, it appears as though we’ve received the “protect yourself from sun message” loud and clear… only one small problem: this message is in stark contrast to the data.
Don’t believe me? Take a look for yourself…
Remember when I mentioned that Australia started their Slip-Slop-Slap campaign in 1981? Well shortly after launching their sunscreen campaign, look at what happened to their skin cancer rates:
These data slides are taken from a presentation done by Ed Gorham and colleague from the Faculty of Family and Preventatitve Medicine at the University of California, San Diego. The following data slides come from their presentation on vitamin D, skin cancer and sunscreen (accessible at: Skin Cancer Sunscreen Dilemna).
Yowsa. That’s a pretty dramatic increase in skin cancer incidence. But one could argue these results are an aberration. Let’s see what other data is out there.
Off to the US where Connecticut, amazingly, has maintained a tumor registry ever since the 1930’s. Why they have such detailed records is beyond me, but I’m not complaining; it makes for a great analysis of historical trends. What do we see there?
Seems that up until about 50 years ago, synthetic sun screens of any kind were non-existent, as were skin cancer rates. Then in Connecticut, like in Australia, there is quite the damning evidence that once sunscreen use became more prevalent, skin cancer rates also rose dramatically. This is not good.
However, before we get too crazy, let’s acknowledge that this data is correlational. I suppose these relationships could be mere happenstance… except when you start to include controlled studies, you get a similar story.
Wow. At best, these data suggest that sun screen doesn’t work. At worst, they suggest that using sunscreen slightly increases your risk of developing skin cancer. Just what the heck is going on!?!?
Let’s consider the human-sun relationship logically for a second. Up until relatively recently on the evolutionary time-scale, humans were exposed to the sun’s rays pretty much 365 days a year without the benefit of sunscreen. We simply wouldn’t have been able to survive in cold climates, therefore we would have migrated to live in relatively warm climates with plenty of sun exposure.
But did our ancestors routinely die of skin cancer while living in warmer climates? Impossible to say, however, we need not only delve into historical speculation. We can actually test the sun exposure = skin cancer hypothesis today.
If sun exposure = skin cancer, if would be reasonable to expect that skin cancer rates would be highest in those areas of the world hovering around the equator, as they get sunshine year-round.
But when we look at these data, tell me what you see:
It certainly doesn’t appear that people living in sunny areas of the world are particularly predisposed to developing skin cancer. Nor is it a slam-dunk argument that only fair skinned individuals get skin cancer, as Eastern Europeans and the Japanese are both quite fair skinned, yet exhibit low rates of skin cancer.
If anything, it seems as though nations that get less sun exposure, or whose vocations tend to be indoors, rather than outdoors seem to be at greater risk for developing skin cancer.
Hmmm… could it be that the fact that humans managed to co-exist with ample sunlight for millennia upon millennia without any problems should tell us something? Might routine sun exposure actually be health promoting? Might our recommendations for sun avoidance be grounded in folly?
If you answered yes, yes and yes, pat yourself on the back. The reason why sun avoidance and an over-prescription of sunscreen makes zero sense has to do with vitamin D production.
Our uncovered skin produces vitamin D following sun exposure. Specifically, our skin produces vitamin D after exposure to UVB light (the wavelength most prevalent between 10 AM and 2 PM). In as little as 20 minutes of UVB sun exposure, a human will produce anywhere from 10,000-20,000 IU of vitamin D.
I know our current recommendation for vitamin D is only 400 IU per day and that you fear producing 20,000 IU of vitamin D might cause you to overdose. I mean, who hasn’t heard that fat soluble vitamins, like vitamin D, are potentially toxic? That the sun’s rays between 10 AM and 2 PM are the most “deadly”? Thankfully, the reality is that you’ve got nothing to fear.
In theory humans can overdose on vitamin D supplements, but one lovely fact about our physiology is that we shut off vitamin D production once we reach an optimal level. Our bodies are pretty smart like that.
Well realizing that our bodies have evolved a mechanism of producing a critical nutrient from the sun and a natural mechanism to cease production when we have enough is certainly comforting. But what about the recommendations saying we only need 400 IU of vitamin D per day?
Turns out that that amount of vitamin D is enough to prevent rickets, but nowhere near the amount needed to optimize your immune system and hormone regulation as a whole.
Now I’ll be the first to caution anyone against deliberately cooking themselves to the point of getting a sunburn. However, even a mild sunscreen, SPF 8, will block over 90% of our vitamin D production.
For a northern nation where UVB sunlight is virtually non-existent from October through April, limiting our already brief window of natural vitamin D production doesn’t seem like all that smart of an idea.
Good Canadian… bad science
But what exactly does vitamin D do for us?
Vitamin D is actually a group of fat-soluble secosteroid hormones. Given that it is a hormone, vitamin D has a wide range of effects on the human system. Among the systems or conditions that benefit from vitamin D are:
- immune system function
- influenza protection
- heart disease
- autoimmune diseases
- chronic pain
- muscle weakness & muscle wasting
- birth defects
- periodontal disease
- and 17 types of cancer!
Phew. That list is quite extensive isn’t it? If you said that vitamin D positively affects every single meaningful healh condition currently affecting humankind, you probably wouldn’t be too far off the truth.
Obviously I’m going to draw your attention to the last point, that increasing vitamin D production protects against 17 types of cancer. Even if we could conclusively prove that excess sun exposure caused skin cancers (and from the data above, it doesn’t really appear that way), does it make a whole lot of sense to increase your risk for all of the above disorders in order to protect yourself from one of the most treatable forms of cancer?
Recently, Dr. Mike Eades (a bariatric doc and someone with a strong appreciation for evidence-based medicine) wrote a couple of brilliant articles about sun exposure and cancer rates. If you’ve got 5 minutes, I strongly recommend you check his most recent post: Heliophobe Madness.
Among the many valuable points he makes, is a stunning comparison between the mortality from skin cancer vs. breast, colon and prostate cancers, three cancers that are linked to a deficiency of vitamin D. He quotes data from the American Cancer Society which reports that in the US in 2009, 40,230 people died from breast cancer, 32,050 from prostate cancer and 51,370 from colon cancer. That makes 123,650 individuals who died from these cancers combined.
By contrast, 8,700 US individuals people died from skin cancer. So even if sun exposure leads to skin cancer, we are pushing an intervention, massive sun screening, to protect against one of the mildest and most treatable forms of cancer, in exchange of increasing people’s risk of developing far more deadly forms of cancer.
Makes sense to me… or not.
Since this post has already gone on forever, I’ll wrap it up here. But if you are interested in learning more about vitamin D and the misguided science behind sunscreens, I suggest you check out this short video:
If you’ve got an interest in learning more about this important topic, I urge you to check out Ed Gorham’s excellent presenation on vitamin D production, sun exposure and sun screens:
Alright now… go enjoy yourself some of the health promoting UVB sunshine. Just don’t try to get an entire summer’s worth of sun exposure in a day
Till next time, train hard and eat clean.