Author: David Bradley

As it is a holiday across the UK today, there is probably little need to warn Brits of the dangers of the sun’s rays, it’s usually so cold and wet, that the chances of frostbite and rust are much higher than sunburn. That said, summer is on its way and a paper in the latest edition of the Lancet medical journal warns that sunscreen and light cotton clothing are simply not enough to protect you from skin cancer caused by exposure to ultraviolet light from the sun.

Instead, the paper’s author suggest that anyone who dares to partake of the great outdoors should wear heavy cotton clothing such as denim, wool, or polyester, to block out those damaging rays. But, should this advice be well taken? Is the sun really to blame for the apparent increased incidence of skin cancer we hear reported or could it be that our car and desk bound sedentary lifestyles in which most people barely see the sun except on their foreign holidays are more to blame for compromising our immune systems and making us more susceptible to skin and various other forms of cancer.

We’ve covered this issue previously in Sciencebase, recent evidence points to a lack of vitamin D (manufactured in the skin during sunlight exposure) as being a much higher risk factor for various cancers than sun exposure itself.

The Lancet Review authored by dermatologist Stephan Lautenschlager of Triemli Hospital, in Zurich, Switzerland, analysed the various sun protection strategies used around the globe. “Wearing sun protective clothes and a hat and reducing sun exposure to a minimum should be preferred to sunscreens,” the team writes, “Often this solution is deemed to be unacceptable in our global, outdoor society, and sunscreens could become the predominant mode of sun protection for various societal reasons, for example healthiness of a tan, relaxation in the sun.”

The Review says that linen and loosely woven cotton represent less effective sun protection and that tightly woven, thick garments made of denim, wool or polyester offer the best protection; not exactly the kind of clothing anyone but heavy metal fans would want to wear on a scorching hot sunny day.

The paper points out that several studies have shown that sunscreen protects against acute UV skin damage and non-melanoma skin cancer, it is not known whether sunscreen stops melanoma developing. And, perhaps therein lies the rub, the connection between sunlight exposure and skin cancer itself is not as cut and dried as some commentators suggest.

“Suggesting wearing denim in hot weather is I think so stupid – it is very uncomfortable. Special clothing is not needed in the UK – on rare very hot days it is better simply to seek the shade – after some exposure to get your dose of D without burning, says Oliver Gillie of London-based lobby group Health Research Forum. He points out once more, that insufficient exposure to sunlight could be doing us more harm than good in terms of increasing cancer risk because of a lack of vitamin D.

“A link between heart disease and insufficient vitamin D is emerging,” he told Sciencebase, “and the National Heart Forum is interested in this aspect of the debate.” Given that until now the sunlight and skin cancer debate has essentially been a Cancer Research UK monopoly, it will be interesting to see how the heart charity approaches the issues.

There have been numerous other research developments that have not seen the media light of day. “There are links with infectious disease,” adds Gillie, “Vitamin D is important for maintaining immune system resistance a fact well-known to those treating tuberculosis a century ago and well before the advent of antibiotics.”

Cancer Research UK says that 90% of melanoma is caused by sun exposure. “This is a very contentious figure,” Gillie points out, “and is disputed.” He adds that it could be that as few as one in ten melanoma cases are caused by sun exposure. “Poor immunity is a big factor in melanoma and people who are on immune suppressing drugs e.g. transplant patients are at high risk,” he says.

Such observations certainly cloud the picture of sun exposure as the big skin cancer killer. He also points out that purported mechanisms for DNA damage and thence skin cancer formation based on the photochemistry of DNA itself no longer stack up because it is now known that melanin, the pigment that gives rise to a tan is a protective agent against the very mutagenic molecules thought to form on sun exposure. Indeed, Raymond Barnhill and colleagues writing in the Journal of the National Cancer Institute (2005, 97, 195-199) found that people with melanoma survive longer if they have more sun exposure. This is doubly ironic in that post-treatment melanoma patients are usually advised to stay out of the sun.

If the British weather is kind for once this Bank Holiday Monday, it will pour sunshine down on all of us. So, leave the denim at home, unless you are a heavy metal fan, and make sure your icecream doesn’t melt while you are sunning yourself.

A female friend of a friend started on hormone replacement therapy (to treat quite severe early postmenopausal symptoms, and on the advice of her GP to reduce the risk of osteoporosis). The symptoms have all but been relieved (although it’s difficult to separate out the effects of the HRT hormones themselves from the phytoestrogens she imbibes from soy milk and other related foods).

Either way, the recent Lancet paper, which received lots of media attention, got her all hot and bothered. She’s an earlier finisher, and is likely to be on HRT for ten years or so, is that going to mean she will get ovarian cancer. The tabloid hype surrounding the paper would seem to suggest so, but as with all statistical health studies that get pounced on by the media it’s worth taking a closer look.

Interpreting the results and scaling up to whole number women, as opposed to fractional women, over 5 years, ovarian cancer incidence for those who have never used HRT was 26 per 10,000. It was 30 per 10,000 for HRT users.

The researchers conclude that, “Women who use HRT are at an increased risk of ovarian cancer. Since 1991, use of previous has resulted in 72 additional cancers per year and 55 additional deaths in the UK.” Their results are based on the million women study, in which 500,000 were HRT and 500,000 were not.

Of course, ovarian cancer is the fourth most common cancer in women in the UK, with some 6700 developing the malignancy and 4600 dying from it every year. The high incidence of deaths is presumably down to the hidden nature of this form of cancer, which is often not detected until it has reached a lethal stage. 72 additional cancers and 55 additional deaths is a significant but not an enormous increase.

The researchers also add that, “In total, ovarian, endometrial, and breast cancer account for 39% of all cancers registered in women in the UK.1 and 2 The total incidence of these three cancers in the study population is 63% higher in current users of HRT than in never users (31 vs 19 per 1000 over 5 years, figure 6). Thus, when ovarian, endometrial, and breast cancer are taken together, use of HRT results in a material increase in the incidence of these common cancers.”

But, these are risk factors and there is simply no way of making any kind of prediction, with current medical knowledge, of whether or not a particular woman on HRT will suffer any form of cancer because of the HRT drugs she is taking. The researchers mention that as HRT use has declined in the US (partly because of the negative publicity it receives), we are also now seeing falling breast cancer rates there.

According to the author of the paper, Valerie Beral of Cancer Research UK, “It is a small but significant risk. It’s more an issue for women to think about how much they want to take HRT to relieve their symptoms against the known risks.”

However, it’s not all about hot sweats and sexual libido, as life expectancy rises in general and the aspirations of older people for a happy and active retirement rises concomitantly, it will be interesting to see whether a few less cancers will be offset by a rise in osteoporosis incidence and the other “side-effects” of the menopause (particularly early onset menopause).

An elderly neighbour of mine has been in and out of hospital with bone density issues and fractures repeatedly and at one point suffered a potentially lethal hospital-acquired MRSA (multiple-resistant Staphylococcus aureus) infection as a result. To my mind, she would most likely not have suffered in this way had she taken HRT during the early menopause. But, equally there is also the thought that had she died of cancer sooner than the osteoporosis kicked in, she would not have suffered bone density problems later in life either.

For every statistic, a counter statistic can be found and when the overall risks are very small it is difficult for the public, the media, and even the medical scientists to know for sure which way to push the agenda.