La tercera afirmación es correcta... pero que se haya infravalorado la peligrosidad de los UV-A no implica necesariamente que los uV-B sean inofensivos

Este es uno de los estudios en los que imagino que te basas pero creo que sacas conclusiones equivocadas, de esto no se desprende que uno pueda lanzarse a tomar el sol a pelo en las horas centrales del día sino al contrario que, incluso aquellos que evitan la exposición al sol en esas horas no deberían confiarse demasiado el resto del día.


12-20-05 - Melanoma Risk Only Partially Associated With Exposure to UVB From Sunlight - News Release - MD Anderson Cancer Center



Otro:

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nadie ha dicho que los UV-B sean inofensivos.

la idea es que si los que te hacen más daño son los UV-A y los que te ponen moreno son los UV-B, tomes el Sol del modo más eficiente, es decir poniendote moreno con la menor exposición a los UV-A, y eso se consigue en las horas centrales y sin protección, y por protección me estoy refiriendo a cremas solares porque si te proteges con ropa obviamente no te vas a poner moreno, que es lo que buscas.

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Sunlight and Melanoma

Sunlight and Melanoma
The Surprising Connection

By William Campbell Douglass, MD

Sunlight may be the best thing for melanoma. That's right, in spite of what you've been reading, the sun doesn't cause melanoma, in fact, it's actually good for you, as many studies have indicated.

Now two more studies are showing the benefits of the sun. Needless to say, this news has left scientists and dermatologists scratching their heads. After all, what else is there to do when what you've been preaching to the masses--that sunlight causes cancer and will kill you--ends up being flat out wrong?

Let me just give you a quick rundown on these articles--both of which appeared in the February issue of the Journal of the National Cancer Institute (JNCI). One evaluated the hypothesis that UV radiation increases your risk of developing lymphoma. But after studying about 7,000 subjects, the researchers concluded that the opposite is actually true: increased sun exposure reduces the risk of non-Hodgkin's lymphoma.

The other study evaluated the supposed link between sun exposure and the chances of surviving melanoma. The researchers concluded that increased sun exposure actually increases the survival rate from melanoma.

So, what could be the cause of such phenomena?
Misconception

Researchers Kathleen Egan, Jeffrey Sosman, and William Blot expressed their ideas about it in an accompanying editorial in the same issue of the JNCI. When they start out with a claim like this one: "Solar radiation is a well-established skin carcinogen, responsible for more cancers worldwide than any other single agent," it's no wonder they would scratch their heads over these latest findings.

And, of course, they're not alone. This misconception pervades the mainstream. In an article published in the London Telegraph, Professor Jonathan Rees, a dermatologist at Newcastle University, said, "The facts of this are that ultraviolet light is the major known cause of skin cancer."
Melanomas and Others

What Rees said may be technically true--the major known cause of skin cancer may well be ultraviolet light. But the type of skin cancer most of these writers are referring to is not melanoma, so the claim paints an inaccurate picture. It's important to make the distinction between melanoma and other skin cancers. Melanoma is a more serious form of skin cancer. It's malignant, and it can spread to your internal organs, often leading to death.

But 90 percent of skin cancers are non-melanoma cancers. The most common forms are basal and squamous cell carcinomas, which are much less serious. They're benign and are easily cured by simple outpatient surgery. These are the ones caused by solar radiation. Melanomas, on the other hand, are most likely caused by lack of sunlight and excess artificial light.

But dare I say there's hope for the mainstream? I don't want to be too hasty in jumping to conclusions, but the JNCI editorial did acknowledge two well-known--though rarely acknowledged--facts: that melanoma is usually found in areas of the body "where the sun don't shine" and that vitamin D may be important in preventing melanoma.

The authors said, "Evidence is beginning to emerge that sunlight exposure, particularly as it relates to vitamin D synthesized in the skin under the influence of solar radiation, might have a beneficial influence for certain cancers."
Known for Years

You don't say.

It amazes me how something known for years, even in the halls of politically correct science, can be ignored by the medocracy until another study is done. Then, voila! It's big news all over again.

The scientific truth about sunlight and cancer is out there--it's just not easy for the average person (or the average doctor, for that matter) to find.

A close look at the Atlas of Cancer Mortality in the U.S., 1950-1994 reveals the amazing truth about sunlight and cancer. Since you won't find this important document at your local newsstand, I'll explain it to you briefly. Among whites in the U.S., there is a striking difference in the number of cases of many types of cancer--breast, prostate, and colon, for example--between the northern latitudes and the southern latitudes. The higher the latitude in which you live, the more likely you are to die of cancer. In other words, New York bad, Birmingham good. And what's one of the major differences between New York and Birmingham? New York gets a whole lot less sunshine.
Toss Your Sunscreen

What excessive sun exposure does do is cause injury to the inner layer of the skin, the dermis, which, in turn, leads to wrinkling of the outer layer, the epidermis. If you're thinking that that happens with age (regardless of the sun), you're right. But sun exposure can speed up the process, causing the skin to age prematurely and to become loose and leathery. This is called solar elastosis (SE).

When researchers at the University of New Mexico investigated melanoma, they found a marked decrease in the disease in patients with solar elastosis. (This information is from one of the JNCI articles I told you about.) In other words, more sun exposure equals less incidence of melanoma. And for those patients who did have melanoma, the subsequent mortality from the disease was approximately one-half as high among those patients with signs of SE. Now, I'm no logician, but it seems to me that if SE is caused by sun exposure and if people with SE have half as much melanoma as people with normal skin, then it's logical to conclude that sunlight prevents melanoma.

In light of these remarkable findings, shouldn't people seriously reconsider the effectiveness and logic of using "protective" sunscreens? What are they protecting you from, a long and healthy life?

Besides the research I mentioned above, I've told you before that the sun is a major source of vitamin D. Not having enough vitamin D can result in osteoporosis, autoimmune diseases, and rheumatoid arthritis, among other things. So when you slather on high-SPF sunscreens, not only are you increasing your risk of melanoma, you're also increasing your risk of developing all of the conditions that can arise from a vitamin D deficiency because you're literally blocking vitamin D synthesis in the skin.

There is a fierce resistance to this obvious fact by the sunscreen manufacturers and the dermatologists who have a reputation (and, in some cases, a sinecure) to protect. Both groups stress sunburn as an important factor in melanoma formation since that's all they have left as a reason to sell you sunscreen lotions. This is a very leaky boat in which to carry their message because (1) millions of people get sunburned every year but very few contract melanoma, and (2) if a melanoma appears, it's still most likely to appear in areas not exposed to the sun.

In the London Telegraph article I mentioned earlier, Jean King, the director of education for the Cancer Research Campaign, severely criticized researchers for defending sunbathing. She said, "There's a very clear and agreed public health message on this issue which we should be careful not to undermine."

Ah yes, an "agreed public health message"--the new paradigm of science that has no scientific justification. Sounds just like fat making you fat. Or fluoride being good for your teeth. But the fluoride paradigm looks like it could be shifting sooner than later.

About the Author

William C. Douglass II, M.D. is editor of The Douglass Report. Reprinted with permission. Copyright 2006, Healthier News, LLC. All rights reserved. For more about The Douglass Report, go to Dr. William Douglass' Newsletter, The Douglass Report.
Editorial Note:

While these studies are provocative and intriguing, we should be careful
before we jump to the conclusion that the more sun to which we are exposed, the better. The first study, finding an increased survival among melanoma
patients with solar elastosis, a sign of chronic sun exposure, compared to melanoma patients without solar elastosis, has multiple interpretations. It is known that there are cellular pathways to the development of melanoma, and it may be that excessive sun exposure causes a less aggressive type, while the more aggressive type has different causes. The second study is more convincing,
because the total incidence of lymphoma was lower among people with increased
sun exposure. Nevertheless, the mechanism is unclear, a connection to vitamin D is speculative, and we must always remember that correlation does not prove causation. The possibility that vitamin D may protect against a variety of cancers has gathered a great deal of evidence, but vitamin D can be obtained both from sunshine and from diet, and it is not necessary to tan or even turn pink in order to maximize one's vitamin D production for any given day. Among the populations studied by Dr. Price, some groups received considerable exposure to sunlight while others almost always covered their skin with clothing. And Price cites a group that sunbathed with coconut oil on their skin, which they thought had nutritional value. But all of these cultures also obtained vitamin D from foods like oily fish, fish livers, fish eggs and butterfat and organ meats from grassfed animals. Thus, we should make sure to obtain plenty of vitamin D from diet and sunshine, but we should still protect ourselves from sunburning or excessive tanning.

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un detalle muy importante para el que no se haya dado cuenta, siempre estoy diciendo que el Sol probablemente no sea el principal responsable del melanoma, no estoy hablando del cancer de piel en general, como se lee en el anterior artículo, hay canceres digamos "benignos" para los cuales la relación con la radiación UV está bien probada y para lo cual la pigmentación de la piel es una gran protección, hasta el punto que estos canceres son inexistentes en la raza negra.

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Sobre este tema, creo que ante todo prudencia. Irse a tomar el Sol de repente a las franjas de máxima incidencia solar, porque de repente "está claro que es bueno" (como antes estaba claro lo contrario) no me parece muy juicioso. Si bien, sólo 20', no creo que sean peligrosos.

Respecto al tema de las razas y su protección pigmentaria:

-Los blancos no están aclimatados a África, sino a Europa. Es más, podría ser según algunas teorías que el Homo Sapiens no surgiera en África, así que...

-Curioso lo de los asiáticos, con, en algunos momentos de la historia, menor incidencia de melanoma que los afroamericanos. No sé si es que la piel amarilla da una protección adicional, o hay otros motivos. Explicaciones hay varias, y pueden actuar a la vez:
.-Que se incluyan asiáticos "oscuros" (hindúes).
.-Que los afroamericanos no sean "tan negros", con una gran proporción de genes blancos y piel menos negra que la de un negro puro.
.-Que los asiáticos salgan menos a la calle o a tomar el sol (por el tipo de trabajo, vida, etc.); no parece raro suponer esto. No dicen en el estudio si han normalizado por cantidad de luz recibida, así que sin esto, extraer conclusiones raciales respecto a la protección de la piel es imposible...
.-Que además de la piel, haya otros factores adicionales (como capacidad de regeneración de tejidos, antioxidantes, etc.). Los asiáticos son famosos por su longevidad.

Ya, pero si resulta que a largo plazo puede ser mucho peor, por una falsa sensación de seguridad, la cosa cambia.

Los japos (que es lo que conozco) no toman mucho el sol... sobretodo las mujeres.

Alli la piel blanca es considerada mas bella para las mujeres, mientras que con los hombres creo que sucede lo contrario.

Tengo un hamijo japo que incluso tiene en su bicicleta un cacharro para poner un parasol.

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gran error, lee las noticias que he puesto de la BBC, si tomas el Sol 20 minutos no te vas a quemar la piel, si lo quieres tomar 2 horas, con la crema no te quemas, pero los UV-A han actuado, por eso están diciendo que la confianza en las cremas que lleva a tomar el Sol más tiempo puede ser la causa del incremento en la incidencia del melanoma, y por supuesto si lo haces fuera de las horas centrales necesitarás esa larga exposición para ponerte moreno.

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ahora que dices esto, fijemonos en europa y vamos a pensar con lo politicamente correcto, que el Sol provoca melanoma y que es principalmente la UV-B, entonces los paises europeos de menor latitud tendrán más incidencia, también aquellos que gozen de más playas y más días soleados y cuyos habitantes más tomen el Sol, hay un pais en europa en que se dan todas estas condiciones, está en el sur y hay muchas playas y Sol, es el que estás pensando, españa, entonces en españa deberíamos tener la mayor incidencia de europa, pues es al contrario, españa tiene la menor incidencia de melanoma de toda europa, tomamos más el Sol que nuestros vecinos del norte y tenemos menos melanoma, pues a ver si va a ser que...

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Entonces los melanomas si no los produce el Sol cual es la causa que los produce?