Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
29 Apr

Why Some Sun Exposure Will Protect You from Deadly Skin Cancer

THE SUNHow does sun exposure relate to skin cancer risk?

The simplistic, popular story is that sunlight exposure has a linear relationship with cancer, similar to how we view smoking. None is safest and each additional minute in the sun will increase our chance of getting cancer. Many people (maybe most) therefore live in a world with danger lurking beyond every shadow, umbrella, overhang, and roof. You let your kid go outside without a layer of sunblock so thick he looks like he’s been smashed in the face with a whip cream pie, and you’re a terrible mother. And don’t even think about the beach unless you’re wearing a burqa. It’s even got a scary name: ultraviolet radiation. Radiation! Isn’t that the stuff inside nucular bombs?

The relationship between sun exposure and skin cancer is far more complex than you’ve been led to believe. While clearly too much sun is a causative factor in skin cancer of all types, it’s not clear what “too much” means. Is there a U-shaped curve where none is bad, some is good, and too much is bad again? What about other factors, like skin color, hair color, propensity to tan versus propensity to burn, and time of day?

We already know that living in areas that get more UV radiation seems to be protective against other types of cancers, like prostate cancer, lung cancer, colorectal cancer, leukemiabladder cancerpancreatic cancerbreast cancer, and lymphoid cancers (I probably could have kept going, but my fingers were getting tired).

Okay, but what about cutaneous malignant melanoma (CMM)? It’s not the most common kind of skin cancer, but it’s by far the deadliest. Is it worth the tradeoff if we increase our risk of CMM?

When we combine the estimated number of annual diagnoses for the cancers I just mentioned in the US, we get a staggering figure: 1,071,000. What about melanoma? 76,100. Incredible, huh? Getting adequate amounts of ultraviolet radiation (scary!) may very well reduce the incidence of cancers that are afflicting over a million Americans each year. Even if the dermatologists and sun alarmists are right and melanoma risk increases linearly with sun exposure and ultraviolet availability, the protection we get against so many other cancers (and the tan, and the sublime feeling of the sun on your skin) might make the tradeoff worth it. That’s clearly, objectively true, at least on the population level. Melanoma just isn’t as large an absolute threat as the totality of other cancers.

Every reader of this blog is likely aware of the importance of vitamin D in the body. The vital pro-hormone, which also comes in supplement form, helps regulate skeletal, cardiovascular, immune, hormonal, and dental health. A deficiency can cause rickets, osteoporosis, muscle wasting, and various hormonal deficiencies. Low levels are linked to heart disease, autoimmune diseases, all cause mortality, and many cancers. These are the systemic effects that get the most attention, but what if the dermatologists and sun alarmists were wrong, or at least a little misguided in their binary opposition to any and all sun? On the surface, it seems counterintuitive that an act that has so many proven anti-carcinogenic and health benefits – getting enough sunlight to optimize vitamin D levels – would increase our chances of getting another type of deadly cancer. It’s possible, but it’s odd.

And there are some other curious facts that muddy the neat, tidy relationship between sun and skin cancer:

Vitamin D (produced in response to UVB exposure) kills melanoma cells. Researchers posit that vitamin D levels around 70 nmol/L may be optimal for protection against melanoma.

There’s also the recent study that suggests smart sun exposure has beneficial, anti-cancer effects at the skin level. Contained within our skin cells are RNAs that do not synthesize proteins, called non-coding RNA. When vitamin D is produced in the skin cells, it triggers these non-coding RNA to go into protective mode. They reduce carcinogenicity and induce tumor suppression. It’s unclear whether oral vitamin D “makes it into” the skin to have the same protective effect. If anything, supplementary vitamin D will deliver the systemic benefits to bone, heart, immune system, and endocrine system thereby reducing the amount we have to produce at the skin level to get the desired anti-carcinogenic effect. But you still need some sun exposure to get it.

Okay, given what we know about vitamin D, it’s easy to buy that it can be protective to a point. Some sun is helpful. Cool. Surely, though, those who get the most sun get the most skin cancer. You have to imagine that outdoor laborers, lifeguards, and other people who spend all day outside in the sun, have way more skin cancer than indoor workers. Right?

It doesn’t seem to be the case:

  • “Recreational” sun exposure – weekend outings, vacations, and other forms of intermittent exposure to the sun – is usually associated with greater melanoma risk than chronic sun exposure.
  • “Occupational” sun exposure – the kind outdoor workers or other groups who spend lots of time in the sun on a regular, consistent basis – is associated with lower rates of melanoma. In fact lifetime sun exposure is associated with a lower risk of melanoma.
  • In Ireland, non-melanoma skin cancer is increasing among the young, urban, and affluent. The authors suggest that the young, urban, and affluent have more free time on their hands, and they’re spending it outdoors. Okay, but the biggest increases in skin cancer in this demographic are occurring in clothed body parts – the swathes of skin that get the least amount of sun exposure.
  • Body parts that get the most sun have the lowest rates of melanoma.

It actually makes sense that going from habitual sun avoidance (working inside all week, getting out on the weekends every once in awhile when you can find the time) to full-on sun exposure (vacation in the tropics, an all day beach excursion) would be bad for you. Indoor skin simply isn’t ready for high UV exposure, and it will burn more easily in response to it. Sunburning definitely increases the risk of melanoma.

Plus, indoor workers still receive UV exposure, just differently. They might see the sun in the morning, through the windows during the day, and after work in the late afternoon. Both morning and late afternoon sunlight have very little vitamin D-producing UVB; it’s almost entirely UVA. Midday sun (you know, the sun they tell you to avoid at all costs) is the only kind with appreciable levels of UVB. And even though office workers get modest levels of sunlight through windows, those windows filter out the UVB and leave only the UVA.

As explained in a 2008 paper (PDF), isolated UVA degrades cutaneous vitamin D while failing to produce any to replace it. So these indoor workers aren’t making any vitamin D and what little they do produce is being broken down from all the UVA they receive.

But wait: although UVA promotes melanoma progression, UVB initiates its formation. Animal models show this. And the connection between sunburns (which are caused by UVB) and melanoma supports it. So isn’t UVB the real problem?

As stated earlier, intermittent and excessive exposures of UVB (“recreational sun exposure”) which often result in sunburns are the problem. It just so happens that the people most likely to get recreational, intermittent, condensed sun are the people who work indoors and go most of the year with low vitamin D – from lack of consistent UVB and from excessive low level window-filtered UVA. People with occupational exposure are getting UVA and UVB in consistent doses, enough to keep the vitamin D levels topped off and nip any budding melanoma cells before they can progress.

How does all this translate to the real world?

Don’t fear a healthy base tan. Contrary to popular opinion, a tan isn’t “already too late.” People who tan well (as opposed to the sun-sensitive types who burn easily) have greater resistance to skin cancer and people who maintain a year-round tan have a lower risk of melanoma.

Avoid burning. Burning is still bad. It’s negative feedback from your body regarding your excessive exposure levels.

Go out at noon. This is when UVB and vitamin D production are highest. The popular advice “that sun exposure should be avoided for three to five hours around noon and postponed to the afternoon” is likely “wrong and may even promote CMM.” Another way to determine UVB availability: go out when your shadow is shorter than you.

Don’t go from zero to sixty. Don’t go from spending the past three months indoors to tanning for hours-long stretches. Work your way up gradually, minute by minute. Start small, especially if light skinned/red haired/blond.

Move around. Don’t “lay out.” You don’t want to expose a single body part to the sun for an extended amount of time. Go do stuff that exposes different parts of your body: garden, lift weights, hike, swim, that sort of thing.

Consider vitamin D supplementation. It delivers the desired systemic effects to bone, heart, immune system, and endocrine system, thereby taking a load off the skin, which can save some D3 for its own protection, and increasing your resistance to the sun. Anecdotes frequently report increased resistance to sunburns upon vitamin D supplementation.

Get your nutrition in check. There are many “internal” measures you can take to increase your skin’s resistance to sun damage. I outlined several of them here.

Get your sleep in check. Our resistance to the sun follows a circadian rhythm, with our defenses strongest in the first half of the day. So you might not want to go tanning after an all-night bender, nor do you want to get too much UVA-rich sun in the late afternoon when your defenses are down.

I hope I cleared up some confusion. If not, feel free to send along any questions.

Thanks for reading!

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. And here I am in the tropical region. 8am-onwards sun exposure will make you perspire, irritated then pass out like a dead meat. I get to maintain a healthy diet and exercise along with my squalene supplement to boost up sun protection and immune system but it’s just sad I can no longer play and walk under the sun.

    Issho Genki wrote on May 12th, 2014
  2. Thanks Mark for sharing some positives about sun exposure. And here I am in the tropical region. 8am-onwards sun exposure will make you perspire, irritated then pass out like a dead meat. I get to maintain a healthy diet and exercise along with my squalene supplement to boost up sun protection and immune system but it’s just sad I can no longer play and walk under the sun.

    Issho wrote on May 12th, 2014
  3. what about carcinoma?
    one seems more vicious tho but i’m confused about the difference

    pam wrote on May 13th, 2014
  4. I think this is really interesting. I’ve long noticed that people who are protected from later in life from sun exposure seem to suddenly start growing numerous skin tags and lesions, which often turn into cancer. This was the case with my grandmother, who had previously spent her life in the sun before being moved to a nursing home where she got none. I’m now noticing the same thing with my mother, who only just recently started protecting herself vigilantly from the sun. She too suddenly has all kinds of skin growths popping up. Yet, I vacation at a beach resort every summer which has a high population of seniors and I’ve noticed those who are constantly out in the sun seem to have no such issues. I developed a personal theory that if you’ve spent time out in the sun during your lifetime, the worst thing you can do is hide from it later in your life!

    Pepper Fee wrote on May 16th, 2014
    • Numerous skin growths appear with age. Just wait a few and you will start finding them too. Seborrheic keratoses, skin tags, angiomas, the list goes on.

      As for skin cancer appearing later in your grandmother…. She is old. Cancers often take time (and multiple serial genetic mutations) to arise. It’s why age is a risk factor for common cancers like chronic leukemia, breast cancer, lymphomas, prostate cancer, colon cancer, and on and on and on.

      Old people are inside more often. Older people get wrinkles as they age. Is it the sun avoidance that causes wrinkles too? Nay. Correlation vs causation, yo.

      Science is NOT the enemy. It’s kinda all we can actually trust. Don’t fear science.

      Blake wrote on September 28th, 2014
  5. re. sun burn,

    i once read a study that people who have had some mild sun burn are less likely to develop skin cancer.

    (don’t ask me — a layman for citation)
    but in terms of hormesis, it seems to makes sense)

    pam wrote on May 24th, 2014
  6. Wow thanks for the shadow advice! I was looking everywhere on internet trying to find how to determine when was the better time to sunbathe according to your latitude and it’s really hard to find.

    Coco wrote on February 21st, 2015
  7. A couple other folks already mentioned this, although what about carcinoma, Mark? It might not be as deadly as melanoma, although it’s still cancer, and considered malignant while it exists. I spent a ton of “recreational” time in the sun in college, and afterward ended up with a basal cell carcinoma (BCC) spot that had to be surgically removed.

    Mitch wrote on April 22nd, 2015
  8. The World’s Only 6 Time Cancer Survivor Savors A Life Well Lived

    Andrew Kuzyk

    Each year right around Christmas, I post a simple message to thousands of folks I’ve never even met, telling them essentially, “I’m still alive.” My oncology doctors told me years ago that “I’m the only six-time cancer survivor in the World” Within days, a tremendous chorus comes back, 175 voices, 500. Many ask, “How did you survive?” They sometimes begin, “Tears are flowing”. A few answer back in kind; “Right there with ya”. It’s now eight years and I am still on this Earth.

    Surviving cancer once, twice, maybe three times may be rare, but six times is simply unheard of. What is in a human being to survive is beyond explainable? We have all heard about survival instinct, but until you are put into a survival situation you have no idea what you are really capable of. I am truly a remarkable fighter who has beaten cancer SIX times, also suffering from Lupus and Alzheimer’s I have defied any and all expectations to reach my 53rd birthday! I am still fighting despite enduring a multitude of cancer operations, including two my surgeons thought I would not even survive. I have every wicked surgery scar to remind me of my 6 multiple battles with deadly cancers.

    Being a feisty father & grandfather from McDonough, Georgia I have fought through so many medical issues it is mind boggling. My health issues began when I was diagnosed with an acute cancerous appendix at the ripe age of 17, I required emergency surgery just before the organ would have ruptured, causing fatal infection to my body. Appendix cancer tends to be rare, affecting an estimated 600 to 1,000 Americans each year. Unfortunately, appendix cancer often remains undiagnosed, like mine was until my emergency surgery. Appendix cancer mysteriously has no known cause. At the time I had no idea I would tangle with cancer yet again soon. I had always been a physically active person. A few months after the bout with appendix cancer, I had several episodes of pain in the upper right quadrant of my abdomen. I thought I may have gallstones and decided to avoid high-fat foods because a high fat diet increases gallstone risk.

    Later that year, however, I started having steady nausea that became constant. I was also having some coronary artery issues and had was scheduled to have several stents surgically inserted. It was in the recovery room after the cardiac stent procedures when I felt unbearable pain in my midsection. My doctor ordered an abdominal ultrasound, which showed irregular thickening of the gallbladder walls. “They couldn’t rule out carsinoma” A surgical specialist reassured me that “cancer was highly unlikely”. “He had done thousands of gallbladder surgeries and rarely saw gallbladder cancer. He said, “It was very rare, and if that were the case, you would probably be dead by now”. Well, my surgeon removed my gallbladder laparoscopically, but the news wasn’t good. Unfortunately, the pathology came back showing T2 gallbladder cancer. I fought the disease by having my cancerous bladder removed before the cancer could invade my entire system. “The statistics for gallbladder cancer are not very reassuring. I went into surgery hoping to live two years.” My wife and five chihuahuas were very supportive during my treatment. “My wife was a blessing to me, always making sure I stayed positive and being so supportive”.

    Two years later, I went to a dermatologist to have a mole examined. I have a condition called displatic nevi syndrome, meaning I have a higher potential for skin cancer than others. My moles are darker than average and tend to turn into the deadly malignant melanoma. Two shave biopsies were performed and pathology tests showed very deep Breslow depths with tumors present in deep margins as well as peripheral. An oncology team referred me to a general surgeon after reviewing my poor prognosis. With deadly stage 4 malignant melanoma, a wide excision surgery was the only radical treatment known to attack and remove the cancer. It is a miracle in itself to survive a stage 4 cancer attack. The cancer left my back looking like a cruel battleground of scars. The surgeon cut as deep as possible, but still did not know if he got it all. I would have to be examined for the rest of my life for the possible return of the deadly malignant melanoma cancer.

    “The toughest one was the renal cell carsinoma “kidney cancer” surgery.” Having a kidney removed was the most difficult of any of the 6 cancer surgeries” Just one year previous, I was forced to have my left leg surgically sawed in half and almost amputated because of infection, to remove a malignant bone tumor lodged in the center of my leg bone. The recovery period for these two surgeries was intense and lengthy. My body now looks like a battlefield with scars everywhere. A major skin graft was taken from my upper thigh tissue to cover the wide excision scars on my back. Somehow I fought through these cancer surgeries through prayer and perseverance. “After one operation, I opened my eyes and the surgeon actually told me the operation was over, but he wasn’t certain if I would pull through, due to serious infection concerns. My 6 multiple cancer diagnoses don’t appear to be based on genetics, just dumb luck.

    Two years after the grim Stage 4 diagnosis, I confessed to a close friend that the doctors had said I realistically only had two years to live, tops. I had kept this information to myself because if I were to say it, then it’s true. I now continue to hold my breath, now that I am now past that deadline. I have spent the last 8 years holding my breath, as I enact every New Year’s resolution, past and future. There’s a small subcategory of people with Stage 4 cancer, it turns out, who live for years after being diagnosed. This group constitutes about 2 percent of all cancer cases. Doctors can’t predict who will fall into this category.

    I told them “I’m a fighter”. Somehow I have managed to fend off the infection and slowly recovered. I pulled through because of my fighting spirit, belief in God and the skill of the surgeons who performed the procedures to remove the deadly cancer. I now fight a myriad of daily health issues including Alzheimer’s disease, diabetes, lupus, heart disease, peripheral neuropathy, and needing both knees surgically replaced. I now live with my wife and chihuahuas in a small basement as the camper we were living in burned down recently, we are barely hanging on to survive these days.

    “I’ve had it tough with the cancer and other ailments I guess” I cannot really do much at all these days. I consider himself a cancer “frequent flyer” being operated on now for 6 bouts with different cancers. “how many people can say that?” I try not to let my physical and mental conditions run my life, but it takes everything that is within me to get through another painful day. If you want to help a friend diagnosed with cancer, just be there. Friends can’t make the fact that you have cancer go away. They can’t make it all better. They can, however, help you feel safer. “when your scared, it’s important to know that someone is there”.

    Andrew Kuzyk wrote on August 8th, 2016

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