WDDTY July 2012 vol 23.4
Most health advice about exposure to sunshine is wrong-and hiding away from the sun is one of the causes of the epidemic of chronic diseases in the UK. We’re told to cover up, seek the shade and wear sunscreen during the summer months to avoid skin cancer, but the advice isn’t supported by scientific evidence. Instead, keeping out of the sun depletes our levels of vitamin D, which can lead to heart disease, diabetes and multiple cancers, and covering our bodies with sunscreens is linked to skin cancer-the very disease that the products are supposed to protect us against.
Even the theory that direct sunlight is the major cause of skin cancer is incorrect, as it may account for just 10 per cent of cases. Indeed, far from causing it, regular exposure to sunlight reduces the risk, and several studies have even found that sunbathing when you have melanoma-the deadliest type of skin cancer-may help to overcome the disease.
Although the UK Skin Cancer Prevention Working Party concluded that “there is no such thing as a healthy tan”, a deep tan does offer further protection, studies have found.
In fact, we should be getting at least 20 minutes of direct sun on most of our body-without sunscreen-every three days throughout the summer months to compensate for the long winter months when sunlight in the northern hemisphere is too weak to replenish vitamin D levels. Reddening of the skin is desirable, as long as you don’t burn. Burning could be a cause of skin cancer, although even this has not been conclusively proved.
Casual exposure to the sun-on our heads and hands when we are outdoors-is inadequate, despite the advice of health experts, who have based their opinions on several small and faulty studies.
And sunscreens may be doing more harm than good. A new study has confirmed that the zinc oxide found in most commercial brands reacts with sunlight and creates free radicals, or unstable molecules, that interfere with the skin’s DNA, thereby increasing the likelihood of skin cancer developing.
The rise of skin cancer
Skin cancer is the most common form of cancer, accounting for around 75 per cent of all cancer diagnoses. Its most deadly form is malignant melanoma, which is responsible for around 1750 deaths in the UK every year, while around 7000 new cases in the UK and 124,000 in the US are diagnosed annually.
However, two other forms of skin cancer-basal cell and squamous cell carcinomas-are far more prevalent and less deadly. More than 60,000 cases of non-melanoma skin cancers are diagnosed each year in the UK, and most are easily treated by having the lesions removed during a simple outpatients procedure. These cancers account for fewer than 200 deaths in the UK each year.
The rate of new cases is accelerating, especially in sunnier regions. Melanoma is six times more common in the northern, more tropical, parts of Australia than in the colder southern regions. Indeed, rates of basal cell carcinoma-the most common of the three types of skin cancer-range from 114 per 100,000 people in Wales to 726 per 100,000 in Australia.
These data, coupled with the fact that melanomas are more common in white people, helped to feed the theory that skin cancer is primarily caused by excessive sun exposure. Medicine believes that around two-thirds of melanomas are caused this way (Arch Dermatol, 1996; 132: 436-42).
Researchers at Memorial Sloan-Kettering Cancer Center in New York say that sun exposure is the “predominant risk factor” for squamous cell and basal cell skin cancers, and is the “only known environmental risk factor” for melanoma-which may be true, but appears to account for just 10 per cent of cases (Haller DG et al., eds. Cancer Management: A Multidisciplinary Approach, 14th edn, online only).
The World Health Organization (WHO) says in the introduction to its own InterSun programme that skin cancer is increasing because “as ozone levels are depleted, the atmosphere loses more and more of its protective filter function and more solar UV [ultraviolet] radiation reaches the earth’s surface” (www.who.int/uv/faq/ skincancer/en/index1.html).
Yet, while the statement appears to be uncontroversial, the evidence does not support it. Professor Johan Moan, of the Norwegian Cancer Institute in Oslo, discovered that the rate of melanoma in Norway increased by 350 per cent in men and 440 per cent in women between 1957 and 1984, a period when ozone levels remained stable (Br J Cancer, 1992; 65: 916-21).
Get with the programme
The high incidence of skin cancer in Australia, and the way the authorities there have tackled it, led to the UK’s own initiative, SunSmart, which is run by Cancer Research UK. This programme adopts almost the identical advice given by the Australian awareness scheme of covering up, seeking shade and wearing sunscreen. The Australian initiative-also called SunSmart-claims to have reduced the incidence of sunburn by 50 per cent and to have slowed the rise in skin cancer deaths, although, again, it is a statement that is not supported by the evidence (Cancer Council Victoria. SunSmart Evaluation Studies no. 6, 2004).
However, as medical researcher Oliver Gillie points out, the Australian sun is far more intense than the sun in the UK, and children in Queensland are exposed to twice as much sunshine as English children. Reddening of the skin happens in one out of every three days’ exposure in Queensland compared with almost zero days in the UK (Gillie O. ‘Sunlight robbery’. Health Research Forum Occasional Reports: No. 1, 2004).
The UK programme was also influenced by the findings of the UK Skin Cancer Working Party, which made its recommendations in 1994. At that time, says Gillie, scientists were not as aware of the vital role that vitamin D plays in our overall health, and so the evaluation did not weigh up the proper risks and rewards of sun exposure.
The UK’s National Radiological Protection Board put to rest concerns about avoiding the sun when it claimed that we could obtain sufficient levels of vitamin D from casual exposure of our hands and face when we’re outside (Health Effects From Ultraviolet Radiation: Report of an Advisory Group on Non-Ionizing Radiation. National Radiological Protection Board, 2002).
The SunSmart initiative has spent millions of pounds on public information campaigns, and claims to have raised awareness of the risks of UV exposure and, as a result, fewer people are interested in tanning, according to surveys it has run. Despite this success, the number of melanoma cases has doubled in the UK over the last 20 years or so.
The campaign also ignores some awkward facts that cast doubt on the skin-cancer theory. Several studies have shown that people who spend a great deal of time outdoors-perhaps because of their occupations-are less likely to develop melanoma, despite their far great exposure to the sun, than people who live and work indoors (Epidemiology, 2001; 12: 552-7). Indeed, those who get burnt because of their infrequent exposure to the sun run a far higher risk of melanoma (Semin Oncol, 1996; 23: 650-66).
Essentially, this suggests the very opposite of the advice we’re given: regular exposure to the sun has a protective effect against skin cancer-and, indeed, against a multitude of other cancers, including those of the breast, colon and prostate-because of the protective effect of high vitamin D levels, which is mainly derived from sunshine (BMJ, 2003; 327: 1228).
In fact, the sun’s cancer-fighting benefits were highlighted in a separate study, which examined 416,134 cases of skin cancer and nearly four million cases of other cancers. This study found that vitamin D production in the skin-that is, from sunlight-decreased the risk of several solid cancers, especially stomach, colorectal, liver and gallbladder, pancreatic, lung, breast, prostate, bladder and kidney cancers (Eur J Cancer, 2007; 43: 1701-12).
Higher vitamin D levels because of regular and moderate sunbathing could reduce the number of
cancer deaths in the US every year by 30,000, claims one study (Prev Med, 1993; 22: 132-40).
Even people who develop melanoma are far more likely to survive if they start getting out in the sun. A study of 528 melanoma patients discovered that those with higher exposures to the sun, or who had even been sunburnt, were far less likely to die from the cancer (J Natl Cancer Inst, 2005; 97: 195-9).
There’s another problem with the sunbathing-melanoma theory: melanomas occur most commonly on the backs of men and upper legs of women, areas that are not usually exposed to the sun (Lancet, 2004; 363: 728-30), while they tend to crop up on the lower legs and soles of the feet of black people (Br J Cancer, 1979; 40: 185-93).
Also, people with melanoma often develop it elsewhere on the body, which has allowed researchers to evaluate the signif-icance of skin and eye colour, and sun exposure. Skin type is an important factor in determining risk, but exposure to the sun accounts for just 10 to 15 per cent of overall risk, which is far from the current belief that it’s responsible for 75 per cent of cases (Am J Public Health, 2001; 91: 360-4).
Other risk factors that SunSmart and other initiatives fail to take into account include obesity, lack of exercise and poor diet, including the consumption of fast food and high-fat snacks (Am J Epidemiol, 1994; 139: 869-80). Drinking large amounts of alcohol can also increase the risk of melanoma (Cancer Epidemiol Biomarkers Prev, 2005; 14: 293), and women who suffer from endometriosis-when the cells that usually line the womb start replicating in other parts of the body-are twice as likely to develop melanoma (Arch Intern Med, 2007; 167: 2061-5).
The rise in cases of skin cancer is in line with increases seen in other cancers, such as breast and prostate cancers, and leukaemia and lymphomas, suggesting that, like them, it is a general lifestyle disease rather than one specifically caused by sun exposure.
Here comes the sunscreen
Another part of the official line on sun exposure is the liberal use of sunscreens, but studies are suggesting that the products may be causing the skin cancers that are blamed on UV rays.
Most commercially available sunscreens contain zinc oxide, which generates free radicals, or unstable molecules, when exposed to the sun’s rays. In turn, the free radicals kill cells, which increase the risk of skin cancer.
Dr Yinfa Ma, at Missouri University of Science and Technology, has demonstrated the process in a series of laboratory tests, and has discovered that it accelerates the longer the zinc oxide is exposed to UV rays. After three hours of exposure to UV light, half the cells that had been placed in a zinc-oxide solution had died, and 90 per cent of cells were dead after 12 hours.
Ma discovered that the zinc-oxide particles released electrons when exposed to UV light, thereby producing free-radical molecules. These bind to other molecules and act as parasites, damaging the ‘host’ molecules. This mechanism is a prelude to skin cancer (Toxicol Appl Pharmacol, awaiting publication).
Sunscreens also contain oxy-benzone (benzophenone-3, or BP-3), a chemical that causes allergic reactions, hormone disruption and cell damage. Although manufacturers insist that the skin does not absorb the chemicals, a report from the US Centers for Disease Control and Prevention (CDC) found that 97 per cent of the 2517 people they screened had BP-3 in their urine. Higher concentrations were found in girls and women, presumably because they are more frequent users of sunscreens and personal-care products that contain sun block. The chemical is also used in lipsticks, lip balm and skin moisturizers (Environ Health Perspect, 2008; 116: 893-7).
Mothers with high levels of BP-3 are more likely to give birth to children who are underweight, a condition that, in turn, is associated with coronary heart disease (CHD), hypertension (raised blood pressure) and type 2 diabetes later in life (Birth Defects Res C Embryo Today, 2004; 72: 300-12). The chemical also disrupts the hormonal system in fish (Toxicol Sci, 2006; 90: 349-61), and causes skin cell damage in humans (Free Radic Biol Med, 2006; 41: 1205-12).
To improve the smell of sunscreens and enhance tanning, most sunscreens include a third ingredient-psoralen, a photosen-sitizing agent. However, Harvard researchers have established that this, too, is a carcinogen (Cancer, 1994; 73: 2759-64).
D is for deficiency
Staying out of the sun dramatically reduces levels of vitamin D, especially for people living in the northern hemisphere, which has infrequent sunny days and long winters when the sun is feeble.
The optimal level of vitamin D is between 100 to 150 nmol/L of serum; yet, the average level for children in the UK is just 52 nmol/L during the winter months, which rises to 80 nmol/L in the summer, which is still below healthy levels. Elderly people in the UK have average levels of 35 nmol/L in the summer and just 23 nmol/L during the winter-a level so low that rickets, heart attack, reduced muscle strength and the risk of falls become very real possibilities.
UV sunlight is the most important source of vitamin D. After synthesis in the skin, the kidneys process vitamin D into its active form, which regulates growth in more than 30 different tissues throughout the body. It controls calcium absorption for healthy bones and triggers apoptosis (programmed cell death), a vital process that prevents cancer. It also restricts cancer growth by stopping the formation of new blood vessels.
Not surprisingly, vitamin D deficiency is associated with the development of 16 different cancers-including melanoma. One study of 502 people with melanoma revealed that, as well
as nervous system disorders such as schizophrenia, cognitive decline and Alzheimer’s, not enough vitamin D can also lead to multiple sclerosis (MS), diabetes (both types 1 and 2), high blood pressure (hypertension), heart failure and heart disease, psoriasis, Crohn’s and inflammatory bowel disease, and rickets, the childhood bone disease.
As we age, we need more vitamin D either from our diet or from sunlight. In a study of 2099 people aged between 70 and 79 years, those with low levels of the vitamin had more problems with moving about, and were twice as likely to be disabled (J Gerontol A Biol Sci Med Sci, 2012; doi: 10.1093/ gerona/gls136).
Another study-this time involving 3262 people aged between 50 and 70 years-found that 94 per cent of them had low vitamin D levels and 42 per cent had the metabolic syndrome, a particular combination of disorders that increases the risk of heart disease and diabetes (Diabetes Care, 2009; 32: 1278-83).
Back to the drawing board
In 2010, a private memo circulated through the offices of Cancer Research UK, which oversees the nation’s SunSmart programme. The note was triggered by worrying health statistics that demonstrated that between 40 per cent and 100 per cent of adult Britons were deficient in vitamin D, and this could be a major cause of chronic disease.
The memo suggested that the charity should draw up new guidelines on sun exposure, and recommend that people get some exposure to the midday sun, when it’s at its hottest. Several private meetings followed, and a new position paper that recommended that people should get “little and often” sun exposure was explored.However, that was as far as the initiative went.
SunSmart continues to recom-mend that we stay out of the sun, as does the WHO, government agencies and the UK’s Chief Medical Officer (CMO) for Health. In the CMO’s ‘Ten tips for better health’, tip number 6 recommends that we protect ourselves from the sun-“cover up, keep in the shade . . . and use factor 15-plus sunscreen”. Each of those recommendations is wrong. Don’t follow them-doing so will increase your risk of chronic disease and even skin cancer; instead, follow the sun.
Bryan Hubbard
Factfile: Topping up vitamin D levels
Factfile: Your optimal vitamin D levels
Vitamin D levels are measured as nmol/L of 25(OH)D in blood serum (2.5 nmol/L = 1 mcg/L).
25(OH)D nmol/L State of health
Factfile: A casual connection
The official line has it that we will get all the sun we need to top up our vitamin D levels from casual sun exposure to our heads and hands when we walk outside. Indeed, lengthy sunbathing will not increase levels further, says the UK’s National Radiological Protection Board.
Although this is an essential part of government-approved health guidelines, it is based on one small-and faulty-study involving just nine people. The group, aged between 70 and 94 years, were in a hospital ward that had a sunny terrace. The patients’ blood levels of vitamin D were monitored for three months-from April to July. When the test started, all of the participants had vitamin D deficiency, increasing their risk of osteoporosis and falls. During the three months of the trial, their vitamin D levels rose marginally, which the researchers considered adequate-yet, they were still deficient or borderline, and certainly their stores were not enough to see them through the winter months.
The only participant with healthy levels of vitamin D had been discharged from the hospital during the trial, and had subsequently spent many hours in his garden, he told researchers (J Nutr Med, 1990; 1: 201-7).
Factfile: A safer sunscreen?
What do you think? Start a conversation over on the... WDDTY Community
