For almost as long as I can remember, we have been cautioned about the need to avoid excess sunlight exposure lest it trigger potentially lethal skin cancer, particularly what is known as ‘malignant melanoma’. Yet, there as for some time been amassing evidence that sunlight exposure is also associated with a decreased risk of several other ‘internal’ cancers including those of the breast, prostate and colon. I and others have argued for some time that because internal cancers are way more common than malignant melanoma, then shying away from the sun is likely to do more harm than good with regard to overall cancer risk. And this week, someone did some number-crunching and appears to have found exactly this.
Johan Moan and fellow researchers from the Institute for Cancer Research in Oslo, Norway have published a paper which dissects the relationship between sunlight exposure and cancer risk. In their analysis, published in the Proceedings of the National Academy of Sciences [1], they assume that sunlight increased sunlight exposure increases the risk of malignant melanoma. I say ‘assume’ as, as the authors agree, this link is far from established. In fact, several lines of evidence suggest that sunlight exposure is not the potent force in the development of melanoma it is so often said to be. OK, let’s err on the side of safety though, and go with the idea that sun exposure does definitely increase melanoma risk.
Against this, as I mentioned earlier, it is necessary to take into consideration the data which show that sunlight exposure reduces the risk of several major internal cancers. This is partly evidenced by the fact that at lower (sunnier) latitudes, cancer incidence is lower than at higher latitudes. We also know that sunlight exposure increases vitamin D production in the skin, and this nutrient is known to have anti-cancer properties. Once all cancers are taken into consideration, the data in the PNAS study support the idea that, in the words of the study authors: “increased sun exposure may lead to improved cancer prognosis and, possible, give more positive than adverse effects on health.”
In a report on this study from Reuters it is claimed that Johan Moan has calculated that if Norwegians doubled their sunlight exposure, the number of annual deaths from skin cancer would rise by 300 (remember, that’s assuming sunlight does cause melanoma), but that annual deaths from other forms of cancer would fall by 3000. In light of this, the idea that ‘increased sun exposure may lead to improved cancer prognosis and, possible, give more positive than adverse effects on health’ does seem highly conservative to me. And it seems even more conservative when one considers that sunlight exposure and enhanced vitamin D levels may not just reduced overall cancer risk, but the risk of several other conditions too including cardiovascular disease.
By way of example, let me share with you the results of another study published this week, that assessed the relationship between vitamin D levels and risk of ‘cardiovascular events’ such as heart attack and stroke [2], This study, which focused on an American population, found that individuals with blood vitamin D levels less than 15 ng/mL were, compared to those with higher vitamin D levels, at a 62 per cent increased risk of cardiovascular disease as assessed over an average of more than 5 years. This increased risk appeared to be confined to people with raised blood pressure. Taking these people on their own, those with lower vitamin D levels were found to be at more than twice the risk of cardiovascular disease. These associations were found even when other factors that at traditionally thought to affect cardiovascular risk (such as physical activity) were accounted for.
And let’s not forget that vitamin D is believed to help protect against other conditions such as osteoporosis, rickets and multiple sclerosis.
Add this to the cancer data just out and there is, I think, overwhelming and compelling evidence to suggest that sunlight exposure is, by and large, a good thing. As I’ve said before, we probably don’t want to be allowing our skin to burn, but with that caveat in place, increased sun exposure looks like it has the capacity to save lives. Lots of ’em. The authors of the PNAS piece allude to this when they say in their paper that: “Authorities should pay attention not only to skin cancer research, but also to research on vitamin D-sun-health relationships”.
Thinking about the wider implications of all this for a moment, I think there is reasonable grounds for suspecting that all this ‘anti-sun’ propaganda we’ve been subjected to will or already has lead to a significant increase in morbidity (ill-health) and mortality. And why? Well, as I’ve pointed out before, one factor here is likely to be the fact that there’s money in sun protection, while sun exposure is essentially free. Though I don’t suppose this is the only example of where an industry might have put profit before people.
References:
1. Moan T, et al. Addressing the health benefits and risks, involving vitamin D or skin cancer, of increased sun exposure. PNAS 2008;105(2):668-673
2. Wang TJ, et al. Vitamin D deficiency and risk of cardiovascular disease. Circulation 2008 [epub before print on 7th January 2008]
In Australia (sunny country) I believe skin cancer is very high. Do you think this is because people are just staying in the sun for too long or there is another reason?
Could it possibly be that people in sunny climates tend to use a lot more sun screen, and it is the chemicals in these products which cause skin cancer??
Just a thought….
Living in the north of Scotland we are short on sunlight for many winter months and I wonder if I should take a Vitamin D supplement?
When I stopped using the sunscreen that my dermatologist recommended, he was furious. I told him that I’d rather continue having the small surgeries to remove my facial/neck lesions than have cancer internally. He does not approve of my method of handling sun exposure but it certainly is working for me.
This gives me the opportunity to thank Dr. Briffa for his excellent newsletter. It’s an antidote for the misinformation and hype that bombards people who use the internet.
So, as a responsible parent with two daughters aged 15 and 16, living in surf-city (Newquay, Cornwall) what should I advise them to do? And is it just vanity that makes me feel better when I am in the sunshine and have a healthy colour?
Carol, in my opinion, one should start off with around 10 minutes in the sun, exposing as much skin as possible. Gradually build up your exposure to the sun daily, and you should find in time that your tolerance increases.
Bear in mind that I have no medical qualifications, but it seems sensible to me.
Carol
Seeing as your daughters are 15 and 16, how about getting them to read the post and see how you feel about it as a family? The general theme here is: ‘get plenty of sunshine but avoid burning’.
Ian in response to comment no. 2
That might be a mechanism. Here are two more:
1. Sunscreens reduce risk of burning but allow more time to exposed to rays that might have cancer-inducing potential in the skin
2. Sunscreens reduce vitamin D production in the skin, which is likely to enhance cancer risk.
In the winter months, from time to time, I get a completely round, red, flat mark that appears on each leg, it takes ages to fade away to a dry, flaky area. My dippsy diagnosis is that it is due to wearing jeans or other protective legwear and so my legs are not exposed to sunlight. I never get these odd bright red marks in the summertime when I wear skirts. What d’ya think?
I found your headline get some sun or die quite upsetting, given my circumstances – I had a malignant melanoma removed in 1994 and especially at the start felt the sun was to be avoided. Too much sun nearly killed me. If the melanoma hadn’t been discovered and removed I would have been dead within 12 months. The advice I was given at the dermatology unit at UCH in London was to keep out of the sun – at least between the hours of 11 a.m and 3 p.m. – and to use sun block. I can see the sense in what you’re saying, however; I have started to sit in the sun – without block – late in the day.
I had a basal cell carcinoma removed from my nose with MOHS surgery when I was 37 yo. The nodule had been there for several years, but without change until I was pregnant and it began to bleed. I am of Irish&Germna heritage, but spent my Northeastern US formative years getting occasion sunburns (though my mother was one of the few who tried to get sunscreens on us). I think the sunburns I got while a teenager and young adult were probably the most damaging (trying to tan like my Italian-American friends, but eventually giving up that futile endeavor).
After my surgery, I moved to So Cal and heeded the advise to stay out of the sun and cover up as well as slather high SPF broad-spectrum sunscreen whenever I couldn’t avoid the sun.
But I think that an all or nothing approach was not good. It’s hard to be sure lack of sunlight was a contributing factor, but over time my moods changed, I became hypothyroid, had gestational diabetes, had trouble sleeping, and was still glucose intolerant. I saw some improvement in these issues since I started to make sure I got a bit of sun (not enough to burn) on a regular basis and supplement with a fairly high dose of Vit D3 (4000 iU/day) plus some cod liver oil.
From what I can find in the melanoma risk info, the connection with sun exposure is not really as clear-cut as we have been led to believe (like so many other health issues, unfortunately). For instance, many melanomas occur where there is little or no sun exposure or even internally. Low Vit D levels seem to add to the risk. For the time being, my interpretation of the sun pros and cons is that I am better off with a bit of regular exposure (using common sense about not burning) than if I shun it completely or slavishly slather on sunscreen.
Helen
Can I preface this answer by saying that it is not intending in any way to make light of your experience.
I would like to make these points though:
The link between sunlight and malignant melanoma is far from cut and dried. The Moan paper cited above discusses the controversy, as it happens.
It may be your belief that too much sun nearly killed you, but with all due respect and treading as sensitively as I can, you can’t possible know that. Maybe you believe it because your doctors told you. But they can’t know either (honestly).
Also, the point of the piece was that there is abundant evidence linking increased sunlight exposure with a reduced risk of many cancers — many of them way more common than melanoma. Could it be, therefore, that without all that sun you got you may have succumbed to some other cancer?
There is no way of knowing the truth about this, but it might help to bear in mind that it is entirely possible that the sun exposure you believe almost killed you may in fact have saved your life.
Thanks for your response to my earlier comment. Yes, the link between the sun and the melanoma was cited by the consultant at UCH – it was made clear to me, by her and others (well meaning, I’m sure), that I should treat the sun with caution and sun block. It is helpful to hear what you say, and Anna’s remarks. As I said earlier, I have started to sit in the sun again, but will avoid burning – cos, apart from anything else, that’s no fun.
“A series of semi-purified diets containing 20% fat by weight, of increasing proportions (0, 5%, 10%, 15% or 20%) of polyunsaturated sunflower oil mixed with hydrogenated saturated cottonseed oil, was fed to groups of Skh:HR-1 hairless mice during induction and promotion of photocarcinogenesis. The photocarcinogenic response was of increasing severity as the polyunsaturated content of the mixed dietary fat was increased, whether measured as tumour incidence, tumour multiplicity, progression of benign tumours to squamous cell carcinoma, or reduced survival… These results suggest that the enhancement of photocarcinogenesis by the dietary polyunsaturated fat component is mediated by an induced predisposition to persistent immunosuppression caused by the chronic UV irradiation, and supports the evidence for an immunological role in dietary fat modulation of photocarcinogenesis in mice.
“In other words, UV-induced cancer increased in proportion to the linoleic acid content of the diet, because linoleic acid suppresses the immune system’s cancer-fighting ability!”
http://wholehealthsource.blogspot.com/2009/03/skin-texture-cancer-and-dietary-fat.html
Since cutting eliminating extraneous linoleic acid from my diet, and ensuring I’m getting enough omega-3, I’ve noticed this myself. I went from a person who would roast after an hour or two in the sun to just having spent five days in Florida without using sun screen and without getting a burn. The change has been remarkable.