skin

Exposure to sunlight prevents melanoma.

Yes, you did read that correctly.

Two independent studies published in the Feb. 2005 issue of the prestigious Journal of the National Cancer Institute (JNCI) squarely contradict the popular myth that UV light causes melanoma.

The first study evaluated the hypothesis that UV radiation increases your risk of developing lymphoma - a hypothesis that had become widely accepted in the 1990s and early 2000s. After studying nearly 7,000 subjects, the authors concluded that the opposite is actually true: increased sun exposure reduces the risk of non-Hodgkin’s lymphoma (NHL) by up to 40%. What’s more, the reduction in risk was dose-related, which means that the more sun exposure someone got, the lower their risk of cancer was.

The second study looked at the link between sun exposure and the chances of surviving melanoma, which is the deadliest form of skin cancer. Guess what? The researchers concluded that increased sun exposure decreases the chance of dying from skin cancer by approximately 50%.

At this point you might be scratching your head and wondering how this could possibly be true, in light of what we’ve been told all these years about the relationship between sunlight and skin cancer. Let’s take a closer look at what explains this phenomenon, and why you likely haven’t heard about it on the news.

Clarification

An editorial published in the same issue of JNCI begins with this statement:

“Solar radiation is a well-established skin carcinogen, responsible for more cancers worldwide than any other single agent.”

This is true. But what the authors neglect to mention is that the type of cancer they are referring to is not melanoma but other types of cancer. Melanoma is the most serious form of skin cancer because it is malignant and can metastasize (spread) to other areas of the body, often leading to death.

But 90 percent of skin cancers are not melanomas. Rather, the most common forms are basal and squamous cell carcinomas, which are often benign and easily cured by simple outpatient surgery. These non-malignant forms of skin cancer are indeed caused by solar radiation (at least according to current research). Melanomas, however, are most likely caused by lack of sunlight or excess exposure to artificial light!

The editorial mentioned two other very important facts that you aren’t likely to hear about from mainstream media sources: that melanoma is normally found in areas of the body that are not typically exposed to sunlight at all (use your imagination), and that vitamin D may be important in preventing melanoma.

Here’s what they actually had to say:

Umm, like, we already knew that.

The role of Vitamin D

It has been known for several years that sun exposure might have a beneficial effect on certain cancers. A 1999 publication of the National Institute of Health (NIH) entitled Atlas of Cancer Mortality in the United States revealed that among caucasians in the United States, cancer mortality for several prominent cancers, including cancer of the breast, prostate and colon, shows a striking latitudinal gradient. Specifically, people living in northern states have much higher rates of these cancers than those residing in the southern states.

The reason for this? Northern states get a whole lot less sunshine than southern states.

As early as 1990 it was proposed that vitamin D, which is synthesized in the skin upon exposure to UV light, might be the agent that accounts for these geographical patterns. (Garland et al. 1990) Less exposure to sunshine means less production of vitamin D. It is known that calcitriol, the active form of vitamin D3, has multiple cellular affects that could confer protection against cancer. The ability to convert the precursor to vitamin D to the active form of D3 (calcitriol) is greatly reduced at northern latitudes, and populations living far from the equator are at increased risk of vitamin D deficiency during the winter months. (Tangpricha et al. 2002)

Even more significant may be the observation that patients with malignant melanoma exhibit low levels of vitamin D3 in their blood, and that others have a problem with the receptor for vitamin D. (Hutchinson et al. 2000; Green et al. 1983) The incidence of melanoma of the skin on sites of the body intermittently exposed to sunlight is reduced among outdoor workers compared with indoor workers. (Elwood et al. 1985)

All of this points to a protective role for vitamin D against cancer in general, and melanoma in particular. But the final nail in the coffin of the “sunlight causes melanoma” hypothesis is this:

A comprehensive review of research studies from 1966 through 2003 failed to show any association between melanoma and sunscreen use! (Dennis et al. 2003)

Say what? Sunscreen doesn’t prevent skin cancer, that’s what.

Does sunscreen contribute to skin cancer?

One thing sunlight does cause is an injury to the inner layer of the skin (called the “dermis”), which leads to a wrinkling of the outer layer (called the “epidermis”). This phenomenon, which happens naturally with age but is accelerated by sun exposure, is called “solar elastosis”, or SE.

Sounds like a bad thing, right? But when researchers at the University of New Mexico studied melanoma, they found a marked decrease in the disease in patients with SE. (Berwick et al. 2005). To put it simply: more sun exposure equals lower risk of melanoma. For patients who already had melanoma, the subsequent death rate from the disease was approximately one-half as high in the group of patients with signs of SE.

I’ll give you a minute to finish cursing the “medical authorities” that have been admonishing us to slather ourselves and our children with sunscreen for decades in order to “prevent skin cancer”. As it turns out, if we followed this advice (and why wouldn’t we have? It sounded logical…) we have actually increased our chances and our children’s chances of developing not just skin cancer, but other cancers as well.

I’m sorry to scare you like that, but I feel I must in order to make this point as clearly as I can:

As we have already discussed, sunlight is a major source of vitamin D. Insufficient levels of vitamin D can result in osteoporosis, autoimmune diseases and rheumatoid arthritis - among other equally unpleasant and life-threatening conditions. When you put on those high-SPF sunscreens, not only are you increasing your risk for melanoma, you are increasing your risk of developing all of the conditions that can arise from vitamin D deficiency because you are blocking your body’s ability to synthesize vitamin D.

And while it is possible to obtain vitamin D from food, it is only present in large amounts in certain kinds of seafood - which many people do not consume regularly. The highest sources for vitamin D in food are anglerfish liver, cow’s blood (I’m not joking) and high-vitamin cod liver oil (HVCLO). It is also present in more modest amounts in chum salmon, Pacific marlin, herring, bluefin tuna, duck eggs, trout, eel, mackerel and salmon.

I’m going to go out on a limb and guess that most Americans aren’t eating these foods on a regular basis. The lack of adequate intake of vitamin D in the diet, combined with habitual use of high-SPF sunscreen and/or lack of exposure to the sun is a perfect recipe for increasing the risk of cancer for children and adults alike.

But you will not hear the sunscreen manufacturers telling you to stop using their product, and you probably won’t hear it from dermatologists in the field who have a reputation (and a history of telling people to wear sunscreen) to protect. They’ll tell you that sunburn is an important factor in melanoma formation since that’s really all they have left in terms of support for selling sunscreen. What they neglect to mention is that 1) millions of people get sunburned every year but very few develop melanoma, and more importantly, 2) if melanoma does appear, it’s most likely to appear in areas not exposed to the sun.

Nevertheless, it’s still probably a good idea to avoid getting sunburned - especially on a regular basis. But it is not a good idea to wear sunscreen, nor is it a good idea to avoid sun exposure.

The idea that sunlight causes cancer and sunscreen prevents it is another mainstream myth that has no support in the scientific literature. Just like the idea that cholesterol causes heart disease, eating fat makes you fat, and fluoride is good for your teeth. (If you still believe any of those statements, check my archives and sign up for my free email digest!)

Before closing, I must mention (briefly) the issue of vitamin D toxicity. Vitamin D is widely considered to be the most toxic of all vitamins, and dire warnings are often issued to avoid excess sun exposure and vitamin D in the diet on that basis. The discussion of vitamin D toxicity has failed to take into account the interaction between vitamins A, D and K. Several lines of evidence suggest that vitamin D toxicity actually results from a relative deficiency of vitamins A and K.
So, the solution is not to avoid sun exposure or sources of vitamin D in the diet. Rather, it ensure adequate vitamin D intake (through sunlight and food) and to increase the intake (through diet and/or supplements) of vitamins A & K. Stay tuned for a future post on the interaction between vitamins A, D & K and their relevance to human health.

In the meantime, this is what I recommend for protecting against cancer and both deficiency and toxicity of vitamin D:

As always, leave a comment or contact me with questions!

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