Malignant melanoma is a form of skin cancer we are repeatedly warned about. As long as I can remember, just as things start to hot up, we are subjected to dire warning about the hazards of exposing ourselves to the sun’s rays. As a prelude to this this year, we have a recently published study which find that those that survive melanoma are at significantly increased risk of having another (compared to the general population) [1]. This study also found that melanoma sufferers are also at heightened risk of other cancers too, including those of the breast and colon, and several types of ‘lymph’ cancers referred collectively as non-Hodgkins lymphoma.
For a variety of reasons, I don’t think it comes as too much a surprise that melanoma survivors are at increased risk of a recurrence of this particular cancer. The effect of underlying factors such as environmental factors (e.g. sunlight exposure) and genetics do not go away overnight, if at all. And then we have the fact that melanoma sufferers are more likely than the general population to be repeatedly scrutinised for the presence of this cancer. In other words, some of the enhanced ‘incidence’ might be due to increased diagnosis, rather than increased risk per se.
But what about those other cancers? Why should melanoma survivors be at increased risk of cancers that have no direct link with melanoma?
One factor that demands our consideration, I think, is vitamin D. My overwhelming experience is that individuals who have had a diagnosis of melanoma become very sun-shy. They have usually been urged by medical professionals to take steps to minimise unprotected exposure to sunlight. This rationale is based on the widespread belief that sunlight causes melanoma. Actually, though, the link here is not as clear-cut as some would have us believe. See here for more about this.
Whether sunlight ‘excess’ is a potent factor in the development of melanoma is a moot point, I think. And what is all-too-often ignored is that fact that if we avoid the sun and slather ourselves in sunscreen when we’re in it, we run the risk of limiting the production of vitamin D in the skin. And higher levels of this nutrient and/or increased sunlight exposure are associated with a reduced risk of several cancers, including – as it happens – cancers of the breast and colon and non-Hodgkin’s lymphoma.
What this means is that when individuals become sun-shy, they are quite likely to increasing their long-term risk of several cancers, as well as several other conditions linked to sunlight/vitamin D including cardiovascular disease and multiple sclerosis.
I advise against burning, but I am vigorously opposed to the generally one-sided anti-sun propaganda we are fed on an annual basis.
One practice I question is the use of sunscreen. There is some thought that this might actually increase melanoma risk [2]. One reason for this is that use of sunscreen generally prolongs sunlight exposure. It has been suggested that while some sunscreens may block ‘tanning’ and burning UVB, they may allow enhanced overall exposure to UVA, excesses of which may induce skin cancer. In this way, some have suggested that sunscreens give a false sense of security.
One other potential issue with sunscreens is that they can stop an individual becoming habituated to the sun. I remember back in the 70s here in the UK using no sunscreen at all even during hot and sunny summers. Shade and appropriate clothing were used to avoid burning when necessary. And by the end of the summer I and my sun-loving would have turned deep brown. By the end of the summer, there seemed no need to take any precautionary methods at all against burning. Tanning is not just a cosmetic thing: it protects the skin and reduces the risk of damage and burning.
I may be looking back with rose-tinted spectacles, but what I see now is a vastly different relationship with sunlight. Even after a sunny holiday abroad I see many people, particularly kids, returning only marginally browner than when they left. Liberal use of sunscreen may well have something to do with this. The apparent lack of tanning is partly significant as it signifies skin that has not become used to sunlight. And this increases the apparent ‘need’ for sunscreen.
In a previous post I suggested that the preponderance of redheads in Scotland may be related to an evolutionary advantage with regard to vitamin D production in the skin. I also referred individuals to a book written by researcher Oliver Gillie which I think quite persuasively makes the point that some of the chronic disease burden in Scotland might be down to lack of sunlight. Oliver Gillie, like me, is concerned regarding the one-sided messages we tend to get re sunlight exposure. He has developed what he has coined ‘SunSafe’ advice.
Here it is:
1. Sunbathe safely and without burning – every day if you can.
2. The middle of the day is a good time for sunbathing in the UK.
3. Start by sunbathing for 2-3 minutes each side. Gradually increase for day to day.
4. Don’t use sunscreen while sunbathing.
5. If feeling hot or uncomfortable, expose a different area, cover up, move into the shade – or use sunscreen.
6. When abroad, where the sun is generally stronger, expose yourself for shorter times until you find out how much is safe.
7. Children benefit from sun exposure, but need guidance.
8. A tan is natural and is generally associated with good health.
The only part of this I personally disagree with is the suggestion in point 5 regarding resorting to sunscreen. Bearing in mind the potential hazards associated with sunscreen use, my preference would be to follow the preceding advice regarding covering up and/or seeking shade.
As I’ve stated before, I have not used sunscreen for over 20 years. My last recollection of sunburn was during a skiing holiday about 20 years ago. I sport a year-round tan and feel well habituated to the sun.
But I still have the capacity to burn, and I act accordingly. In the summer in southern Europe, for instance, I can often be found in middle of the day on a beach in a tee-shirt and straw hat. As the sun cools off during the afternoon, off come the tee-shirt and hat. I’ve learned over the years how to get my sun, and the benefits it promises, without sunscreen and without sunburn. I have a strong sense I’m healthier for it too.
References:
1. Bradford PT, et al. Increased Risk of Second Primary Cancers After a Diagnosis of Melanoma. Arch Dermatol. 2010;146(3):265-272.
2. Garland CF, et al. Could sunscreens increase melanoma risk? Am J Public Health 1992;82:614-615
The vitamin D council advise that your body will only benefit from the sun’s rays, when you are taller than your shadow. So at this time of the year, in England, we gain no vitamin D at all from sunlight, even at midday.
Bill
If it’s accurate, that’s a very useful rule of thumb.
Margaret
I’ve never heard of this before. Actually, it seems the opposite is true. See http://www.drbriffa.com/blog/2009/06/22/vitamin-d-helps-to-combat-tuberculosis-flu-and-other-infections/
I wonder is there any evidential basis for contemplating if it is possible that fair skinned people can become ‘seasoned’ to exposure to the sun.
This is a line of thought and in no way intended to be considered advice, I just wonder if other individuals (or studies) have made similar observations.
I am fair-skinned myself and have spent a lot of my working life indoors or under cover. However, there was a period where I spent more time working out of doors.
In the former scenario I would likely not get a lot of sun exposure and would lack a tan until the arrival of some free time coincident with one of those uncommonly sunny days of a British high summer. On such days I would have to manage my exposure to avoid burning.
On the other hand, when I worked predominantly out of doors I would find that I would build up a tan and some seeming degree of resistance to burning progressively with the seasonal improvement in the weather. So notwithstanding the oft repeated cautionary note that overexposure to sunlight contributes to skin aging, then to what extent does a tan function as a sun-block?
However, I observed something further in myself. It is normal for a tan to fade over the winter, of course, but if I had become ‘seasoned’ and tanned from working out of doors in one year then come the next year I found my paler skin seemed to have less of a tendency to burn and a more willing tendency to tan. I’d say the tendency was even more pronounced with successive years. So I wonder if the obs of others and/or the literature concur with my seeming experience? Moreover, if so what agents may determine the skins response to solar and UV exposure?
I had pulmonary tuberculosis during childhood and adolescence and I was told to avoid being in the sun, particularly to avoid sunshine on the chest area. I was told that sunshine (or strenuous exertion or stress) could ‘awaken’ dormant TB bacteria and thereby cause a recurrence of the illness after it had apparently healed. I did actually suffer recurrent bouts of the disease.
Was this advice about sunshine re-awakening TB correct advice? Do they still give this advice to people with TB? Or was it purely myth/invention? Does anyone know?
I have blogged on this recently as the anti-sun message is something we are bombarded with here in New Zealand. A scan through the evidence returns some interesting findings that I would love someone from the Cancer Society to explain:
At What Time Should We Go Out In The Sun?
To get an optimal vitamin D supplement from the sun at a minimal risk of getting cutaneous malignant melanoma (CMM), the best time of sun exposure is noon. Thus, common health recommendations given by authorities in many countries, that sun exposure should be avoided for three to five hours around noon and postponed to the afternoon, may be wrong and may even promote CMM.
Moan J, Dahlback A, Porojnicu AC. At what time should one go out in the sun? Adv Exp Med Biol. 2008;624:86-8. Department of Radiation Biology, Institute for Cancer Research, Montebello, Oslo, Norway.
How strong is the evidence that solar ultraviolet B and vitamin D reduce the risk of cancer?
…Results for breast and colorectal cancer satisfy the criteria best, but there is also good evidence that other cancers do as well, including bladder, esophageal, gallbladder, gastric, ovarian, rectal, renal and uterine corpus cancer, as well as Hodgkin’s and non-Hodgkin’s lymphoma. Several cancers have mixed findings with respect to UVB and/or vitamin D, including pancreatic and prostate cancer and melanoma. Even for these, the benefit of vitamin D seems reasonably strong. Although ecological and observational studies are not generally regarded as able to provide convincing evidence of causality, the fact that humanity has always existed with vitamin D from solar UVB irradiance means that there is a wealth of evidence to be harvested using the ecological and observational approaches.
Grant WB.How strong is the evidence that solar ultraviolet B and vitamin D reduce the risk of cancer?: An examination using Hill’s criteria for causality. Dermatoendocrinol. 2009 Jan;1(1):17-24.
Increased UVA Exposures & Decreased Cutaneous Vitamin D3 Levels May Be Responsible For The Increasing Incidence Of Melanoma.
Cutaneous malignant melanoma (CMM) has been increasing at a steady exponential rate in fair-skinned, indoor workers since before 1940. A paradox exists between indoor and outdoor workers because indoor workers get three to nine times less solar UV (290-400 nm) exposure than outdoor workers get, yet only indoor workers have an increasing incidence of CMM.
Godar DE, Landry RJ, Lucas AD. Increased UVA exposures and decreased cutaneous Vitamin D(3) levels may be responsible for the increasing incidence of melanoma. Med Hypotheses. 2009 Apr;72(4):434-43. Epub 2009 Jan 19.
What stands out from the above paper to me is the line:
A paradox exists between indoor and outdoor workers because indoor workers get three to nine times less solar UV (290-400 nm) exposure than outdoor workers get, yet only indoor workers have an increasing incidence of CMM.
Someone isn’t telling the full story me thinks.
Dr. Briffa,
Regarding sun exposure and vitamin D, what do you do regarding showering with soap and water relative to when you were out in the sun? I’ve read some claims that absoprtion of the vitamin D produced can take up to 48 hours and that this washing can potentially impair that process. Do you have any information along these lines?
And regarding using shadow as a rule of thumb, I would say that this isn’t necessarily something I’d focus on. For example, while it’s early in the year where I am (downstate New York, USA), I still go out as close to midday as possible in order to start building up a tolerance to the sun. So while I definitely think the shadow rule of thumb can be a helpful one, I think there’s still a broader picture to be looked at. Or maye I am just looking for any excuse to get out in the sun and enjoy it, even in March 🙂
Dr. Briffa,
I’ve heard Dr. John Cannell of the vitamin D council say this in a radio interview and I think on a video lecture.
This is an extract from a reply to a question to Dr. Cannell:
“While it is true that your shadow must be shorter than you are to make vitamin D, the shorter the shadow the more the D, and the relationship is not linear.”
March 2009 newsletter, about a third of the way down the page.
http://www.vitamindcouncil.org/newsletter/2009-march.shtml
It’s a very simple explanation, that everybody can understand.
Bill says:
The vitamin D council advise that your body will only benefit from the sun’s rays, when you are taller than your shadow. So at this time of the year, in England, we gain no vitamin D at all from sunlight, even at midday.
Bill & John – this is an accurate rule of thumb. It relates to the angle at which UVB radiation strikes the earth at the latitudes that the likes of UK & NZ sit at. With the sun below 45deg during solar noon (tall shadows), UVB will refract at an angle where it will miss the surface of the earth. Above 45deg (short shadows), UVB strike increases allowing vitamin D synthesis (allowing for other factors such as clarity of the atmosphere, etc).
regarding washing and vit D …I understand that it is in the natural skin oils that the conversion of UV rays to vit.D takes place….if this is true then we maybe shouldn’t shower too soon after sun exposure or even soap our skin too often! But leading on from that thought, the older you get the drier your skin becomes so if you moisturise your skin should you use an oil as close to our own in composition (if so which one) or is the composition immaterial ?
Regarding washing and vitamin D….
I have read this too. I mentioned the possibility of delayed absorption from skin here http://www.drbriffa.com/blog/2009/12/04/light-appears-to-have-powerful-painkilling-properties-for-some-people/
I think the idea of avoiding soap/detergent for a day or so after sun exposure (perhaps using soap/detergent on non-sun-exposed parts such as armpits, groin etc) is certainly worth a try.
Having been a pale skinned blue eyed blonde kid I was constantly being brought in as a child out of the sun. Raw egg white was the cure for sunstroke if I recall that far back. A nice scientist on a long haul flight told me that the angle of the sun determined how burned you got. Hence all the mediterranean tours were off limits to me.
Having decided to take Blue Green Algae which is reputed to remove heavy metals, I find that I do not burn and now get a good but light tan in the tropics. I do not burn in Oz or California/Mexico which means I can go out longer in the sun without using any sun screen and feel better for it. Going on a tour in Oz I had to produce a tube of sunscreen or I could not go on the trip, I think I still have it here unopened.
One thing has puzzled me, like you Dr Briffa, when I had my Vit D3 tested it was quite low, only 45 on second reading. I wonder if our Vit D absorption has gone into hibernation through avoiding it? My sister in Oz took two years to get her level up to 92 from 19. I wonder which is the most detrimental, avoiding the sun and putting on so much sunscreen or not getting enough sun or the time to go out and enjoy it and still being told to cover up totally? Are we likely to be born deficient in Vit D from ones Mother? Its a very serious problem in Queensland she says.
Now I am taking 10K daily I’m beginning to feel a bit more bright eyed, and have more energy – being older I probably need more.
Chris and Liz: I am also very fair-skinned. I grew up in the tropics and subtropics and spent a lot of time out of doors. I never had anything you could call a tan, but I didn’t burn either (except for one adolescent occasion when I lay out in the sun for hours to “sunbathe” with my friends and ended up with blisters).
After moving to England I lost that protection, whatever it was, and burned easily even in the feeble rays at this latitude.
But now, having achieved high blood levels of vitamin D by supplementation, I find that I burn rather less easily. Might vitamin D itself somehow protect agains sunburn?
This whole business of being taller than your shadow for sun avoidance is a complete red herring. If anyone has any evidence why there is a sudden cut off point in angle or time of year I’d be very interested to hear it.
The truth as any physicist or meteorolgist will tell you is that the incidence of UV is a function of cloud cover, ozone levels in the stratosphere, the presence of aerosols in the atmosphere, the local reflectivity of the earths surface and elevation. The angle of the sun is another factor. Before examining the angle of the sun lets look at some of the others.
Local reflectivity:- Ever wondered why you get so sunburnt when skiing in winter?
Elevation:- Ever wondered why Nepalese mountaineers get so suntanned?
Angle of the sun:- The reality on this oft quoted factor in UV irradience levels is not refraction, but down to the fact that at an oblique angle the suns rays are spread more thinly. They also have more atmosphere to pass through. These two facts are the pertinent ones when considering seasonal variation in sun UV exposure. What these fact point to is that the UV you get is variable and dependent on numerous factors. Go out on a snowy and very sunny day in December all day and you will get a vitamin D boost!!
Hi Doc,
Been meaning to ask you for ages:
I read an article suggesting that if you shower immediately after sun or sunbed exposure you lose the potential Vit d synthesis. Is this true and if so, how long should you wait?
(as an aside, I’m currently using a sunbed for a few mins every other day to build up some “base coat” for a trip to Cuba. Fewer aches and pains since I started too!!!)
Thanks.
Suzanne
I’ve commented on this (comment 11)
Robin wrote:
“This whole business of being taller than your shadow for sun avoidance is a complete red herring. If anyone has any evidence why there is a sudden cut off point in angle or time of year I’d be very interested to hear it.”
Robin, have a look at the following link that shows a distinct drop off in UVB radiation levels in Christchurch, New Zealand from February until Sep/Oct. There is seasonal variation in UVB at higher latitudes – a fact that is well known.
“The truth as any physicist or meteorolgist will tell you is that the incidence of UV is a function of cloud cover, ozone levels in the stratosphere, the presence of aerosols in the atmosphere, the local reflectivity of the earths surface and elevation. The angle of the sun is another factor.”
Agreed. Winter air is more dense, holds more particulate, and therefore will more likely scatter UVB radiation (less so UVA). But where I live (low atmospheric pollution), on a crystal clear autumn day, once all the other factors (that I cannot see) are accounted for, the biggest factor remains the angle of the sun relative to the horizon. The closer it is to the horizon, the less UVB will be striking the surface (for all the reasons you pointed out). Coincidentally, when the sun is low to the horizon, I’ll also have a long shadow…
“Before examining the angle of the sun lets look at some of the others.
Local reflectivity:- Ever wondered why you get so sunburnt when skiing in winter?”
Because you are up a mountain, in clearer air, and what little UVB radiation is available is concentrated by the snow crystals and reflected back (like a magnifying glass can concentrate light). I’d imagine too, that the places you can ski in Europe are closer to the equator than northern UK or southern NZ.
“Elevation:- Ever wondered why Nepalese mountaineers get so suntanned?”
Because the Himalayan mountains are closer to the equator and closer to the sun than UK/NZ, and the atmosphere is cleaner. The Nepalese are there all day everyday, so they have long term exposure by which to build up a nice tan.
“Angle of the sun:- The reality on this oft quoted factor in UV irradience levels is not refraction, but down to the fact that at an oblique angle the suns rays are spread more thinly. They also have more atmosphere to pass through.”
So what happens when you shine weak light at an oblique angle through a thick prism? It scatters. And what is scattering of light if it isn’t bending or refraction? Basic high school physics there.
“These two facts are the pertinent ones when considering seasonal variation in sun UV exposure. What these fact point to is that the UV you get is variable and dependent on numerous factors.”
I think that is the entire point isn’t it? UVB radiation is highly variable and dependent on numerous factors. This makes it difficult to get a consistent supply of vitamin D via skin photosynthesis, leading to increasing levels of vitamin D deficiency and the associated health issues that go with this.
“Go out on a snowy and very sunny day in December all day and you will get a vitamin D boost!!”
Really? Just on hands and face? Good luck with that one.
Sorry – link for Christchurch study here:
http://www.nzma.org.nz/journal/120-1262/2733/
Dr. Briffa,
With respect to your comment “I think the idea of avoiding soap/detergent for a day or so after sun exposure (perhaps using soap/detergent on non-sun-exposed parts such as armpits, groin etc) is certainly worth a try.”, would this take some getting used to for someone who is able to get regular access to midday sunlight that is sufficient to produce vitamin D (based upon location and many of the other factors touched upon) and who also tended to shower once every day?
For example, if able to get sun every or almost every day in a week, it wouldn’t leave much time for washing, but then again this is something I’ve likely been conditioned into doing without actually thinking about how necessary a practice it is at certain times. Plus when I took an oral vitamin D supplement, I never thought twice about soap and showering, but now that I am looking to at least give the sun more of a chance, it seems to be something to focus on more.
@ Valda,
Might vitamin D itself somehow protect against sunburn?
I share that exact same curiosity with you.
The personal experience of a contrasting reaction to being out in the sun that you describe is a similar experience and point I was trying to get across in (4) above.
Clearly different people react differently to sun and their response can vary across some notional axis of burning or tanning so skin tone and genetics may play a part in determining variability between individuals.
But you and I have experience and observation to suggest that there may also be a variable response within individuals. Dr Briffa used the term ‘habituated’ the context of his blog and I used the term ‘seasoned’ in the context of registering my point.
If being seasoned or habituated to a healthy degree of frequent sun exposure in some way improves the skins response to the sun and reduces likelihood of burning then what candidates may mediate the process?
I was thinking on the fly to wonder, like you, if vitamin D status itself may have a role in determining any distinction between tanning and burning. People contribute that raising vitamin D status can be slow in response to intervention and this facet may have some synergy with the year on year experience I had.
Did I read somewhere that cholesterol is a precursor to the synthesis of vitamin D? Still thinking on the fly, does cholesterol status – perhaps raised ‘bad’ cholesterol – correlate with low Vitamin D status?
Chris & Valda,
The NZ sun is known for being particularly viscious, and with me being of good celtic stock, I did tend to get burned quite quickly. However, for the past 2 summers, over a period in which I have been heavily supplementing with vitamin D & omega 3 oils, I can generally stay out in the sun all day (I generally do not purposefully sunbathe) with little more than a little bit of reddening & I’ll go to tan relatively quickly. Others I work with have noticed the same.
This is a great paper, which whilst not specifically mention vitamin D, does mention many other nutrients that may confer a degree of sun protection.
http://biology.kenyon.edu/courses/biol113/2006-2007/Readings/annurev.nutr.24.012003.pdf
Given the state of most people’s diets, it comes as no surprise that many are getting sunburned quicker, more deeply, and are having to suffer the consequences. As per usual, conventional wisdom points the finger at the wrong culprit, choosing to blame the sun that has been there for several billion years, rather than the actions of man & the world he has created for himself over the last 50 years.
Jamie,
Thankyou for your detailed reply.
On the 1st point (and most others) I agree with all that you say. The study from NZ is interesting, but their conclusion only confirms my final point that UV radiation will produce vitamin D in the body at all times of the year. I’m not saying that you will get very much vitamin D in winter in mid-high latitudes, but I’ve often seen statements from large organisations as well as in blogs that imply none is available. This is obviously incorrect.
A minor point, but scattering is a different physical process from refraction, which strictly speaking concerns changes of the speed of light in mediums of different density. The bottom line is that the uvb in the 295-300nm range that produces most vitamin D3 still gets through in winter, it is just a question as to how much is available. Given the huge amounts generated by brief exposure to the sun in summer 10000-50000IU I would expect that it would certainly be worth going out on a snowy, sunny winters day and expecting to get a top up that is almost certainly greater than that available from say a cod liver oil supplement.
Robin,
I guess the difference is between whether there is no UVB in absolute terms or practical terms. As long as the sun continues to emit UVB, there will always be some. Whether I would want to expose that much skin to that much cold air for that long in the middle of winter to make a paltry 1000IU, is a different matter. That said, I’m more likely to be able to do that than say, an elderly gentleman, or a young child.
Physics… UVB… yes. Practicality for humans in sub-zero temperatures… No. Not at least when pills can be swallowed.
The Vitamin D Council’s latest newsletter (available online) made mention of 2250IU (from recollection) per day of vitamin D giving someone approx 12 days storage. If prolonged cold temperature low UVB exposure nets you less than that on a daily basis (which I suspect it would), I can’t really see much point.
There is no doubt that sun causes wrinkles. Just look at the inside of your arm if over a certain age compared to the outside. If you care about that or looking older get the sun on your legs not face or neck.
Jamie,
‘NUTRITIONAL PROTECTION AGAINST SKIN DAMAGE FROM SUNLIGHT’, the link you supply above, is one interesting paper. Up to yet I have only scanned it. It all seems worthy of detailed study but the section on lipids quickly caught my attention. I derived a sense that the quality of fats supplied by the diet rather than the quantity of fats has implications for the skins response to exposure to sunlight. This has something in common with a paper on Heart Disease, Dietary Fat Quality and Coronary Heart Disease Prevention: A Unified Theory Based on Evolutionary, Historical, Global, and Modern Perspectives.
I’d agree with your sentiments. The Human is a species whose dominant majority has innovated itself out its’ natural habitat via innovation in diet, lifestyle, and social behaviour, and suffers in many ways as a result. Humans, particularly the western developed ones, are far too clever for their own good, but not nearly wise enough to benefit anthropologically.
Chris,
The paper discusses the benefits of low fat eating for sun damage resistance. My suspicions are that a low fat diet isn’t required, but rather a diet low in n-6 PUFA. Any study where a low fat (40-50% of TEI), yet my sun protection seems to have improved this summer.
I am another NZ redhead. My brother, who lived in the UK for the last 20 years of his life, died of melanoma recently. My initial reaction was to be very phobic about the sun, but since reading Michael Horlick’s book I realise this is the wrong approach. I now aim for consistent all-year sun exposure, in the middle of the day by preference, without sunscreen.
Dr Briffa, returning to this thread several months on I had forgotten how informative the thread was. Jamie was particularly succinct in the choice, assembly, and wisdom of the following words;
While actively seeking reference to something partly related elsewhere on the ‘web I found these comments beneath something or other;
During the course of evolution we have shed significant amounts of bodily hair to become the ‘naked ape’. Furthermore, there have been evolutionary changes in skin pigmentation that show (some) correlation with habitat (where in the world our more recent ancestors come from). It should not come as a surprise, surely, that our skin and some kind of ‘healthy’ exposure to the sun should be a mechanism in promoting optimal health?
Perhaps, as was something that ran through the comments, the problem with the sun is not so much the sun itself, nor with exposure, but that in our present environment and lifestyles we have become somewhat ‘maladapted’ through not being satisfactorily ‘habituated’ or ‘seasoned’.
According to one horizon Michael Nortons’ advice to cover ones rude bits would seem sound sense. On another horizon an option might be to discriminantly apply high factor sunscreen to those regions, and viewed from a further horizon good advice might be to expose those ‘rude bits’ more frequently but for metered and moderated duration.
.. .. How did matters become so complicated?