Being tanned seems to be synonymous of healthy and beautiful, but, is this new aesthetical fashion, lasting for some decades now, a trend that may cost us not only a good part of our health but even our lives?
Is it sensible to literally spend hours under the sun?
I had the pleasure to interview Dr. ROBYN LUCAS, from the National Centre for Epidemiology and Population Health (Australia) on the effects of overexposure to ultraviolet radiation as well as the environmental effects on immune function to find out exactly what ‘prize’ is at the end of this particular beauty contest.
SRM: Thank you Dr. Lucas for participating in this interview, I really appreciate it. The health authorities have not ceased, especially during this last past decade, to alert the population of the increased levels of ultraviolet radiation and the adverse effects resulting from overexposing to this radiation.
However, many people use sun beds and sun tanning lamps in the winter, and spend endless hours in the sun in the summer, thinking that they are not in danger of developing any related disease. From your knowledge, would you please share what diseases are developed and within what timeframes they are developed, after overexposure to ultraviolet radiation from artificial or natural sources?
DR. ROBYN LUCAS: Ultraviolet radiation, either from natural or artificial sources, does not penetrate far into the body. This means that the affected tissues are those at the surface of the body – primarily the skin and eyes.
There is now very good evidence that ultraviolet radiation is the leading cause of skin cancers including melanoma and the non-melanoma skin cancers (basal cell and squamous cell carcinoma). It is also an important cause of cataracts of the eye, and diseases of the eye surface (eg pterygium) that may affect vision. There is some evidence that ultraviolet radiation contributes to the development of melanomas of the eye.
The skin is also an important part of the immune system, and there is growing evidence that UV exposure of the skin can result in changes in immune function both at the site of the exposure but also for immune function in the rest of the body.
For example, cold sores represent reactivation of a viral infection that has been kept dormant in the body – too much sun exposure causes a lowering of immune control of the virus, and active infection ensues. What is of key importance is that these adverse effects are the same for both natural and artificial UV sources.
There are both immediate effects of too much UV exposure – sunburn, snow blindness, reactivation of the virus that leads to cold sores for example – and effects that do not become apparent for many years – skin cancers, cataracts and so on. We know that for some diseases, eg melanoma and possibly basal cell carcinoma, childhood sun exposure may be very important for the development of a disease that may have its onset well into adulthood. One problem with these delayed-onset diseases is that it can be difficult to pick up the effects of changes in sun exposure behaviour until many years after those changes occurred. We are only now starting to see changes in skin cancer incidence in Australia, after 30 years of active sun protection messages.
SRM: Not all exposure to ultraviolet radiation is harmful as you have explained in numerous articles and essays, and, in fact, our bodies and minds need this exposure in some amount. Why is important to receive some of this radiation and what should we do to find out what amount of it is just the right amount? Also, what illnesses could be alleviated with some controlled exposure to ultraviolet radiation?
DR. ROBYN LUCAS: Some level of sun exposure is required for the synthesis of vitamin D. Most people get very little of their vitamin D requirement in their diet – unless that diet is high in oily fish. So our main source of this vitamin, that is essential for the maintenance of healthy bones, is from sun exposure of our skin – the UV radiation causes chemical changes in a precursor molecule in the skin that starts a cascade leading to production of the active form of vitamin D.
While it seems likely that ANY exposure to ultraviolet radiation increases the risks of those diseases noted earlier, that increase in risk is probably very small for the type of moderate UV exposure required for vitamin D synthesis. It is important to note that vitamin D synthesis does not keep increasing with longer time in the sun – in fact, after a certain amount is made, more sun exposure actually causes degradation of the vitamin D. So frequent shorter exposures are both more efficient for vitamin D production and less likely to result in sunburn and the longer term adverse effects of sun exposure.
It is very difficult to give a general message on the right amount of sun exposure. Fair-skinned people burn more easily, but make vitamin D more easily too – so they need less sun exposure than people with darker skin. Elderly people seem to make vitamin D less easily and so may need more sun exposure than a younger person. If you live in a very sunny place (closer to the Equator), then you will make vitamin D more quickly than if you live in a higher latitude place – so recommendations for time in the sun for Australians are not directly transferable to Britain.
Also, it is better to expose a lot of skin for a shorter period of time, than a little skin for a long time.
It is possible to measure a person’s vitamin D status with a blood test – people who are worried that they are not getting enough vitamin D (e.g. those who live and work largely indoors, dark-skinned people living in a not very sunny environment, people who mainly cover themselves with clothing when they are outside) can ask their doctor for this test.
There has been an explosion of research into the possible health importance of vitamin D status in the last 5 years. We know that vitamin D is important for bone health, including prevention of osteoporosis and there is mounting evidence that higher levels of vitamin D may decrease the risk of cancers of the large bowel (colon). There is also quite a lot of research that indicates that higher levels of vitamin D, or of sun exposure, may decrease the risk of some autoimmune diseases such as multiple sclerosis and type 1 diabetes. But I emphasize that vitamin D is made very quickly on exposure of the skin to the sun – sunbathing, sunburn, and typical length solarium sessions are not required for maximal vitamin D synthesis and may impede it.
SRM: You are, indeed, an expert in determining environmental effects on immune function. Could you, please, describe what some of these interactions between the environment and our immunological responses are?
DR. ROBYN LUCAS: The skin is an important defense against environmental challenges -eg. bacteria etc.- and has a very active immune system. UV exposure of the skin results in changes in the local immune system – one example of this is suppression of the normal controls on the development of aberrant cells, and this contributes to skin cancers being able to develop. But chemical messages from the immune cells in the skin are also taken back to the rest of the body, so that UV exposure of the skin can affect immune responses far from the site of the skin exposure.
One positive effect of this is that we think that through this mechanism UV exposure may dampen down the over-reactive immune response to the body’s own tissues that results in autoimmune diseases such as multiple sclerosis and type 1 diabetes. Of course there may also be adverse effects of such immune suppression – one of these is that the immune response to vaccination may be impaired by sun exposure around the time of vaccination. This would mean that the vaccination was not as effective as expected – and the vaccinated person may not be protected from the target disease.
Of course, nothing is straightforward in this field! Vitamin D also seems to be important in immune function, and is the source of a bacteria-killing chemical found in blood cells – so maintaining good vitamin D status is also important to optimal immune function. Again, sun exposure needs to be balanced – some sun exposure is essential for vitamin D synthesis and for optimal immune functioning; but too much sun exposure results in adverse effects on the eyes, skin and immune system.
What have been your findings and conclusions so far in this area?
DR. ROBYN LUCAS: Stratospheric ozone blocks out most of the harmful short wavelength UV radiation coming from the Sun: so stratospheric ozone depletion occurring during the latter part of the 20th century posed a serious risk to Earth’s health.
Fortunately there was rapid international action to limit CFCs that were causing the problem, and ozone levels are gradually recovering. Climate change is likely to have serious effects on human health, through increase in heat-related deaths, air pollution, increase in extreme weather events and so forth. And international action on this global environmental change has been anything but rapid.
There are likely to be many interactions between ozone depletion and climate change that have implication for human health – both atmospheric interactions, eg. hotter lower atmospheric temperatures will result in a delayed recovery of stratospheric ozone, but also in human behaviours, whereby warmer temperatures encourage greater sun exposure. Both of these effects may lead to increased risks of the adverse effects of sun exposure.
SRM: Dr. Lucas, could you affirm, based on your studies, that immunological and carcinogen diseases are increasing due to the current state of our environment at a global scale?
DR. ROBYN LUCAS: There is considerable evidence that the incidence of immune diseases such as multiple sclerosis and type 1 diabetes are increasing, over a time period that implicates environmental exposures as risk factors. Skin cancer incidence is also continuing to increase in most parts of the world – because of the lag period between excessive exposure and development of the skin cancer these increases are still reflecting high sun exposure many years ago. It is not just our environment, but changes in the way that we are interacting with our environment, that is increasing the risks of these diseases.
SRM: How is this correlation between ambient ultraviolet radiation and type 1 diabetes established?
DR. ROBYN LUCAS: We examined data on the incidence of type 1 diabetes in Australia, from a national registry. We looked at the location of residence of all new cases of type 1 diabetes in children 0-14 years of age, and used satellite data to calculate the level of ultraviolet radiation at that location.
What we found was that type 1 diabetes incidence decreased with increasing ambient UV levels (which is what we had expected, based on other research), but in areas of high population density, ie. cities, this pattern reversed. That is, in cities, higher levels of ambient UV were associated with higher incidence of type 1 diabetes! We believe these findings reflect that in rural areas there is a much closer correspondence between ambient UV levels and the dose received by children, than occurs in cities – because rural children are outside more. In cities, as UV levels increase, children may be kept inside, or heavily sun protected, so that the actual UV dose they receive is lower – and this increases their risk of type 1 diabetes.
SRM: What message then would you send to the thousands that spend hours of sunbathing at the beach or the swimming pool?
DR. ROBYN LUCAS: Be aware of your skin type – if you are fair-skinned and burn easily, use sun protection (sunscreen, clothing, shade, sunglasses) and don’t deliberately sun expose. Don’t get sunburned. Short exposures to a greater exposed surface area are much better than long exposures to a smaller area, for vitamin D synthesis. Don’t use sunscreen to prolong the time you can spend outside. In summer you can probably get sufficient UV to make vitamin D from very short exposures (especially if these are in the middle of the day) – anything more than that is just increasing your skin cancer risk without additional benefit for vitamin D.
SRM: Thank you very much for your advice and expertise.
So there you have it, folks, sunbathe with moderation and… naked.