Sunshine, Sunscreen, Cancer, and Vitamin D

sunscreen-coppertoneThere seems to be a current belief, reinforced by the medical profession, that sunscreen should be applied whenever there is any risk of sun exposure at all.

The reality is, as always, more nuanced, and considerable research indicates excessive use of sunscreen will actually increase the risk of cancer. And anyway, if sun is bad for you, why isn’t the entire human race black? Skin pigment is a great natural sunscreen. If sunshine were dangerous, natural selection would have sorted this one out millions of years ago. Instead, skin color is regulated. The body tans when it needs to let less sunlight through, pales when it needs more. A seasonal adaptation. There are also longer-term adaptations. Contrast Norwegians and Nigerians.

And like many natural, regulated processes, the medical profession has latched onto a piece of the puzzle and undertaken various “improvements.”

At the core is this notion: sunshine causes malignant melanoma. While frequent, intense sunburn will increase the risk, the actual cause is unknown. Malignant melanomas are frequently found in places that receive no sunshine at all, and sharply increased use of sunscreen does not seem to be stemming the rise of this disease, and may be actually increasing it.

In fact, this sun-cancer idea has so much attention, that there is a huge overuse of sunscreen these days. This will have detrimental effects. Here are some confounding facts we will have to digest in order to make informed decisions:

  • The cancers known to be caused by the sun, basal and squamous skin cancer, are common, easily treated, and, unless ignored, rarely fatal. This risk is so small that it poses no reason to avoid the sun.
  • Complete avoidance of sunlight increases the risk of more serious cancers.
  • The serious skin cancer is malignant melanoma. However, it frequently appears in places that get no sunshine. Dr. Mike found one between a patient’s toes. (When was the last time your doctor examined you there?) So clearly, some melanoma is not caused by the sun.
  • A normal amount of sun exposure reduces overall cancer risk.

So malignant melanoma is the real problem, and the connection to sunshine is partial at best.

This raises a couple of questions.

  1. What, exactly, is the relation between sunshine and malignant melanoma?
  2. What is the optimal strategy?

We will try to answer these.

Malignant melanoma appears to be associated in part with repeated severe sunburn. This makes sense, and would explain why Nordic people have a greater incidence. Lancet, the top British medical journal, summarizes this well, “Exposure to intense bursts of ultraviolet radiation, especially in childhood, starts the transformation of benign melanocytes into a malignant phenotype. Paradoxically, outdoor workers have a decreased risk of melanoma compared with indoor workers, suggesting that chronic sunlight exposure can have a protective effect. Further, some melanomas form on sun-exposed regions; others do not.” Another research paper can be viewed here.

This gives us a clue to the optimal strategy: avoid intense bursts of ultraviolet radiation—severe sunburn.


No clue what this is about

The current medical practice is to avoid all sunshine, and supplement with vitamin D to compensate for one of the (many) deficiencies the avoidance of sunshine will cause.

This is quite short sighted. First, how much vitamin D? The pills contain amounts like 100 to 400 IU/day. An hour at a swimming pool on a sunny day will generate 12,000 IUs. How would one know whether to supplement? A blood test would work, but it isn’t likely many will do this. Further, the benefits of sunshine aren’t solely about vitamin D. There are numerous other processes that are in some way dependent on sunshine; vital processes which sunscreen is likely to also derail. Here again is a case of interfering with Mother Nature, a common practice in the medical profession, and one that has, almost without exception, made matters worse. (Substituting transfat for butter would be a good place to start this discussion.)

Let Your Body Figure It Out

That suntan you do or don’t get is sunscreen, and the optimal amount. Generally, if you only worry about the extreme conditions (no sun or too much) your body will take care of the rest and will tan you up to the amount needed to take in the healthiest amount of sun.


A Good Occasion for Sunscreen

More specifically, (and this isn’t rocket science), the sun exposure curve is “J” shaped. Too little is bad, too much is bad. Where is the optimum? The solution is simple. Enjoy the benefits of sunshine. Save the sunscreen for the beach or the mountains. A little sunburn, the kind that is slightly red and goes away the next day, isn’t a problem, and, of course, the more a person tans, the more protected they are. Remember: suntan = sunscreen.


Excessive Use of Sunscreen?

It is important to bear in mind that moderate sunshine is protective. Our bodies are optimally adapted to the sunshine levels where our hunter-gatherer ancestors lived. Of course, we don’t have those addresses, but we can guess from the colors of our skins. Dark skinned people in northern climes probably need more sun than they can get, and certainly do not need sunscreen. And pale Scandinavians should take care to avoid sunburn.

Science sidebar.

About UV.

Why is ultraviolet light a problem? Light is a form of electromagnetic radiation. So are are radio waves, wifi, x-rays, and gamma rays. These “rays” are waves and have a “frequency” associated with them, meaning how frequently they go up and down. They are waves after all. At the beach (remember the sunscreen) a wave of water might be crashing every 10 seconds. This would mean a frequency of 0.1 waves per second. Radio wave are in the millions per second, and wifi in the billions, and it goes on up. So what? Well, the higher the frequency, the more it can penetrate us and do some potential cellular damage. Radio wave and wifi don’t penetrate, light, a higher frequency still, just starts to. But it doesn’t penetrate to the progenitors cells. (Progenitor cells are “junior” stem cells. Info here.) These are below the skin, and are responsible for generating all our new skin. It is these cells that can become cancerous. Going up in frequency, we come to ultraviolet. These can penetrate a few millimeters. This is enough to hit, and possibly damage the progenitor cells in the skin. Higher frequency UV is yet more dangerous as it penetrates deeper. X-rays, higher frequency still, can pass right through our body, gamma rays are higher yet and can penetrate a bank vault. Any of these penetrating rays can slam into a cell nucleus and damage it. If that cell happens to be one that reproduces (a stem or progenitor cell) then the damage can be reproduced as well. These are the seeds of cancer.



  2 comments for “Sunshine, Sunscreen, Cancer, and Vitamin D

  1. Jim
    April 26, 2016 at 6:36 am

    I often wonder if our light-skinned northern latitude ancestors (maybe a couple millennia ago) started their warm season with a sunburn before getting their tan or if they were cautious (wise) and worked up to a great tan.

    • April 26, 2016 at 8:17 am

      Great thought experiment, Jim. My guess has always been that the slow emergence of light intensity as early Spring merged into Summer took care of this. The Texas sun of my youth cooked my hide; that part is for sure. I’m missing half of my nose from skin cancer. Fortunately I had a plenty to spare: thank you, Neanderthal ancestors. Dr. Mike

Leave a Reply

Your email address will not be published. Required fields are marked *