By: Becklund BR, Severson KS, Vang SV, DeLuca HF–
Although the exact cause of multiple sclerosis (MS) is unknown, a number of genetic and environmental factors are thought to influence MS susceptibility. One potential environmental factor is sunlight and the subsequent production of vitamin D. A number of studies have correlated decreased exposure to UV radiation (UVR) and low serum 25-hydroxyvitamin D(3) [25(OH)D(3)] levels with an increased risk for developing MS.
Furthermore, both UVR and the active form of vitamin D, 1alpha,25-dihydroxyvitamin D(3), suppress disease in the experimental autoimmune encephalomyelitis (EAE) animal model of MS. These observations led to the hypothesis that UVR likely suppresses disease through the increased production of vitamin D. However, UVR can suppress the immune system independent of vitamin D.
Therefore, it is unclear whether UVR, vitamin D, or both are necessary for the putative decrease in MS susceptibility. We have probed the ability of UVR to suppress disease in the EAE model of MS and assessed the effect of UVR on serum 25(OH)D(3) and calcium levels.
Our results indicate that continuous treatment with UVR dramatically suppresses clinical signs of EAE. Interestingly, disease suppression occurs with only a modest, transient increase in serum 25(OH)D(3) levels. Further analysis demonstrated that the levels of 25(OH)D(3) obtained upon UVR treatment were insufficient to suppress EAE independent of UVR treatment.
These results suggest that UVR is likely suppressing disease independent of vitamin D production, and that vitamin D supplementation alone may not replace the ability of sunlight to reduce MS susceptibility.
By: Amanda Chan–
People who have had lifelong exposure to high levels of sunlight are less likely than people with less exposure to develop multiple sclerosis, a new study suggests.
The risk of having a preliminary symptom of multiple sclerosis decreased by 30 percent for every 1,000 kilojoules of exposure to ultraviolet light, the study said.
These levels of sun exposure were accumulated over a lifetime (you might be exposed to 6 kilojoules of UV light on a summer day), so people shouldn’t sit in the sun for extended periods of time without sunscreen and expect to lower their multiple sclerosis risk, said study researcher Dr. Robyn Lucas, a fellow at the National Centre for Epidemiology and Population Health at Australian National University.
“There is strong evidence that the risks of high doses of UV radiation in a single exposure greatly outweigh any possible benefits,” Lucas told MyHealthNewsDaily.
The benefits coming from higher vitamin D levels were already known, but because it was sun exposure that this study linked to decreased multiple sclerosis risk, it’s possible that only sun-generated vitamin D — and not that provided by food sources or vitamin D supplements — provides those benefits, Lucas said.
The findings of the study appear tomorrow (Feb. 8) in the journal Neurology.
The importance of sun exposure
Researchers looked at the sun exposure histories of 216 Australians, ages 18 to 59, who had an early sign of multiple sclerosis but were not diagnosed with the disease, as well as 395 people who did not have any MS symptoms. The participants reported how much sunlight they were typically exposed to, and the researchers also measured their skin damage from sun exposure and their melanin levels. The participants’ vitamin D levels were measured by blood tests.
Over their lifetimes, people in the study had been exposed to 500 to 6,000 kilojoules of UV light. Researchers found that those with the most skin damage from sun exposure were 60 percent less likely to have had a first sign of multiple sclerosis than people who had the least damage.
And people with the highest vitamin D levels were less likely to have a first sign of multiple sclerosis than people with the lowest vitamin D levels, the study said.
The researchers also found that multiple sclerosis was 32 percent more common in the Australian regions farthest from the equator than the regions closest to the equator — a difference they attributed to differences in sun exposure, vitamin D levels and skin type.
The secret to vitamin D’s effects
This study’s findings revealed the relationship between the first sign of multiple sclerosis, called the first demyelinating event, and sunlight, said study researcher Anne-Louise Ponsonby, an epidemiologist at Murdoch Children’s Research Institute in Australia.
The first demyelinating event can appear as a loss of sensation in a limb, blindness in one eye, or weakness in one limb that lasts more than 24 hours, Ponsonby said. Most people who have such an event will go on to develop multiple sclerosis in 10 years. The disease is diagnosed after a second event.
Vitamin D is known to affect immune cells, and the immune system plays a significant role in spurring multiple sclerosis, said Dr. Tom D. Thacher, an associate professor of family medicine at the Mayo Clinic in Rochester, N.Y., who was not involved with the study.
While the study showed that increased sun exposure is linked with a reduced risk of multiple sclerosis, it does not prove that vitamin D prevents the disease, said Thacher, who wrote an article on vitamin D insufficiency published last month in the journal Mayo Clinic Proceedings.
“Other factors besides vitamin D that are related to sun exposure could be responsible for protection from multiple sclerosis,” such as melanin production from getting a suntan, Thacher told MyHealthNewsDaily.
A study published last month in the journal Multiple Sclerosis found that people who had sufficient levels of vitamin D had higher levels of antibodies to the Epstein-Barr virus, which is linked to increased risk of multiple sclerosis.
“Low vitamin D may predispose people to certain viral infections,” said Dr. Ellen M. Mowry, author of that study and an assistant neurology professor at University of California, San Francisco, who was not involved with the new study. “Since some viral infections have been associated with MS risk, low vitamin D could also influence MS by this mechanism.”
Increased sun exposure and higher vitamin D levels may help to protect against the risk of developing multiple sclerosis, a new Australian study suggests.
Multiple sclerosis is an autoimmune disease whose symptoms include loss of balance, slurred speech, muscle spasms, and difficulty walking or moving the legs or arms. Focused on residents living in Australia, the study also echoed prior findings that this disease of the brain and spinal cord strikes with greater frequency among people who live in less sunny regions farther from the equator.
Study co-author Anne-Louise Ponsonby, a professor, epidemiologist and public health physician with the Murdoch Children’s Research Institute at Royal Children’s Hospital in Melbourne, stressed that the exact mechanism by which sun exposure and vitamin D may help protect against a “multi-factorial disease” is not yet clear.
But vitamin D is an important agent that helps modify immune system functioning, she noted, “and laboratory studies have shown higher vitamin D levels can dampen down some of the adverse immune overactivity that occurs in autoimmune diseases such as MS.”
Ponsonby and her colleagues conducted their research with the support of the National Multiple Sclerosis Society of the United States of America, the National Health and Medical Research Council of Australia, the ANZ William Buckland Foundation, and Multiple Sclerosis Research Australia. Their observations are published in the Feb. 8 issue of the journal Neurology.
Exposure to the sun results in increased vitamin D levels, since the body makes vitamin D when it is exposed to the ultraviolet B rays in sunlight.
Although past research (some conducted by the same research team) has uncovered a similar association between sun exposure and MS risk protection, the authors noted that the current finding is the first to examine the impact of sun exposure among individuals who are just experiencing precursor signs of MS, but have not yet actually been diagnosed as having the disease.
This approach, the investigators noted, ensured that the new analysis is focused solely on pre-disease sun exposure patterns, rather than sun exposure routines that might be altered after a diagnosis. (Sunlight exposure has not been shown to benefit MS patients after diagnosis.)
Between 2003 and 2006, the research team looked at 216 patients between the ages of 18 and 59 who had early pre-diagnosis signs of MS. The patients were located in one of four different locations in Australia, with latitudes ranging from 27 degrees South to 43 degrees South.
Almost 400 other study participants without any disease indications were also included in the study for comparative purposes.
All were asked to report how much time they had spent in the sun over weekends and holidays during both summer and wintertime over the course of four different time-frames: between the ages of 6 and 10; 11 and 15; 16 and 20; and during the three years leading up to the study. In addition, skin exams were conducted, and blood samples taken to measure vitamin D levels.
The result: the higher the amount of both past and recent sun exposure (as well as specifically leisure-time exposure), the lower the risk for developing early signs of MS.
Specifically noting that sun exposure ranged from 500 to 6000 kiloujules per meter squared, the authors found that for every additional 1000 kilojoules of exposure, the risk of developing the first signs of MS dropped by 30 percent.
In addition, having a higher vitamin D level was also independently linked to a lower risk for developing MS.
What’s more, those living in the study regions furthest away from the equator faced a 32 percent greater risk for signs of MS than study participants who lived closest to the equator.
And lastly, those with the most signs of skin damage faced a 60 percent lower risk for developing initial indications of MS compared with those with the least amount of skin damage caused by the sun.
While advising that sun exposure “should not be discouraged,” Ponsonby strongly cautioned against the sort of “excessive exposure” that can give rise to a number of adverse health consequences, including possible skin cancer.
Dr. Moses Rodriguez, a professor of neurology and immunology at the Mayo Clinic in Rochester, Minn., agrees that “it’s all about not overdoing it”.
“Dermatologists can get up in arms with these sorts of studies because they’re saying that the amount of sun exposure that you would need to get protection against something like MS would be the amount that would increase your risk for melanoma and skin cancer dramatically,” Rodriguez said.
“But in truth, it appears that your mother’s idea to go out and play in the sun was not necessarily a bad idea,” Rodriguez added. “It’s just that everything has to be tempered. You don’t, for example, want someone to go take 10,000 units of vitamin D. Yes, you need some sun exposure, and you need some vitamin D. Both appear to have some protective effect in terms of MS. But neither is the whole answer, and neither is going to cure MS.”
Nicholas G. LaRocca, vice president of health care delivery and policy research at the National Multiple Sclerosis Society in New York City, praised the study for advancing scientific knowledge about MS.
“I do think this is a very important study,” he said. “It really moves this field forward in terms of refining our understanding of what puts people at risk for developing MS, and what might reduce this risk.”
But like Rodriguez, he also cautioned against “over-interpreting the implications of the current findings.”
“Reading this [study], one might be tempted to say ‘well, I should move to a sunnier climate’ or ‘I should dose myself with tons and tons of vitamin D,'” LaRocca said. “But I don’t think we know enough to really understand what the full and most appropriate implications are. There are many contributions to MS risk, so we will need a lot more research before it becomes clear what’s really going on.”
No-sunshine lifestyles are putting an increasing number of Indian infants at the risk of bone deformities, seizures and poor growth, a significant new study of Vitamin-D prevalence among newborns and their mothers has shown.
Conducted by paediatricians from the All-India Institute of Medical Sciences (AIIMS), the research, for the first time, provides evidence to the government on the urgency of Vitamin-D supplements for pregnant women being covered under the national health programmes across the country. The study reveals acute Vitamin D deficiencies in exclusively breastfed babies and even greater shortages of the vitamin in their mothers.
Of the 98 healthy infants (aged 2.5 to 3.5 months) and their mothers studied for the purpose (47 enrolled in winter and 51 in summer to determine seasonal variations in Vitamin D prevalence, if any), the researchers found shockingly high combined prevalence of Vitamin D deficiency in 86.5 per cent infants and 92.6 per cent mothers. Among those with severely deficient levels, the paediatricians found hyperparathyroidism (a condition wherein the thyroid glands secrete large quantities of parathormone to maintain low calcium levels in the body) in 90.3 per cent infants and 73.1 per cent mothers. They further found evidence of radiological rickets (babies wrists were X-rayed to find if they had rickets due to low Vitamin D and calcium levels) in 30.3 per cent infants.
“The presence of hyperparathyroidism among infants and mothers with low Vitamin D levels proves low calcium levels in their bodies and is clear evidence of Vitamin D shortage. It is to make up for calcium loss that thyroid glands secrete parathormone in greater quantities resulting in a condition called hyperparathyroidism. The parathormone maintains calcium levels in the body by mobilising calcium from bones to the blood. Long-term effects of such a mobilisation include bowing of legs among children, seizures marked by cramps of hands and feet and their abnormal posturing, or even abnormally square-shaped heads,” Dr Vandana Jain, assistant professor, paediatrics, AIIMS and lead author of the study told The Tribune. She said the newly found high prevalence of Vitamin D among Indian infants and their mothers was higher than that in the US but consistent with that in Greece, the UAE and Pakistan. The deficiency of Vitamin D in India is even lower for girls, starting from adolescence, with a recent study finding 90.3 per cent schoolgirls reporting such deficiency.
“Vitamin D deficiency among infants and mothers in both summers and winters can be attributed to decreased cutaneous synthesis of Vitamin D due to higher skin pigmentation in India. But the primary reason appears to be less exposure to the sun, lack of participation in outdoor activities and excessive use of sunscreens by women, who block UV rays essential for the skin to synthesise Vitamin D,” Jain added, recommending 15 minute exposure of arms and legs to the sun from 10 am to 3 pm daily.
The most important takeaway from the report is Vitamin D supplement for pregnant and lactating women in India, as is recommended by the American and European Academies of Paediatrics. The AIIMS study argues for the Indian Association of Paediatrics to make a similar recommendation to the government, which could consider providing supplements in the national programme.
Read the article here: http://bit.ly/gGTXC6
A 12-year-old girl with vitamin D deficiency has been told that her condition could have been caused by using strong sun cream.
Tyler Attrill used factor 50 cream which, according to her consultant, could have deprived her of the essential vitamin and caused the bone disease rickets.
BBC Breakfast’s resident GP Rosemary Leonard gave her advice for sun exposure.
The Institute of Medicine (IOM), a health arm of the National Academy of Sciences, has just released its long-awaited vitamin D supplementation recommendations. To the disappointment of the world’s leading vitamin D scientists, those recommendations make a mockery of an exhaustive body of scientific research.
The IOM suggests that 600 international units (IU) of supplemented vitamin D3 per day is ideal, and that a blood level of 20 ng/ml is sufficient for optimal human health. The IOM also suggests that supplementation with higher quantities of vitamin D could be harmful and that there are no randomized controlled trials to prove the safety or efficacy of higher levels of supplementation.
The Sunlight Institute declares that the IOM’s recommendations are ill-conceived and dangerous for the following seven reasons:
1. Extensive research indicates that if there were no other dietary source of vitamin D, 600 IU per day in adults would produce a blood level, on average, of about 6 ng/ml, a level so low that it correlates to the occurrence of the disease osteomalacia or “adult rickets.” Incredibly, in the press conference, it was stated that 600 IU would be adequate at the North and South Poles.
2. The IOM considers the 600-IU-per-day recommendation, added to dietary sources and sunlight exposure, to be sufficient for optimal health. In reality, little vitamin D is present in foods. For example, three glasses of vitamin D-fortified milk provides only 300 IU; 3.5 oz. of farmed salmon, 200 IU; a glass of fortified orange juice, 100 IU totaling a mere 1,200 IU per day including the IOM-recommended 600 IU supplement. Sunlight exposure, the most natural and productive source of vitamin D, could easily fill in the gap to a 2,000 IU level during the summer, but in the winter, north of latitude 340,(On a line from Los Angeles to Atlanta, for example) little or no vitamin D is produced. In the northern US and in Canada, “vitamin D winter” (the time during which the body cannot produce any vitamin D from the reduced amount of available sunshine) lasts for several months. Ninety-five percent of Canadians are considered (by non-IOM measures) to be D deficient in winter, and Americans in the Northern states are not much better. A 600-IU supplement plus the IOM’s recommended food sources is a recipe for a winter health disaster, which may include highly increased susceptibility to colds, influenza, cancer, heart disease MS, septicemia and numerous other maladies. It was also stated at the IOM press conference that the average American gets 200-300 IU from food.
3. Vitamin D blood level of 20 ng/ml are not really even sufficient for bone health, and that number sets research back several years. The “normal vitamin D range” printed on laboratory blood-test results prior to 2005 was from 8.9 ng/ml to 46.7 ng/ml. Based on newer research findings, that range changed after 2005, and lab test results began carrying the statement, “Recent studies consider the lower limit of 32 ng/ml to be a threshold for optimal health” with a reference to research conducted by Dr. Bruce Hollis who is widely regarded as one of the world’s top vitamin D scientists. (Hollis BW. J Nutr 2005;135:317-22) Dr. Hollis stated: “The current adult recommendations for vitamin D, 200-600 IU per day, are very inadequate when one considers that a 10-15 min whole-body exposure to peak summer sun will generate and release up to 20,000 IU vitamin D-3 into the circulation.” Hollis has also established that pregnant and lactating women need as much as 6,000 IU daily to provide for their own and their infants’ needs (Hollis, BW. J Bone Miner Res 2007;22, suppl 2:V39-44). The IOM’s low recommendations attempt to take us back to the Dark Ages of vitamin D knowledge.
4. The fact that up to 20,000 IU of vitamin D can be produced by sunlight exposure (the natural source of vitamin D) defines the IOM recommendation of 600 IU as being ludicrous. 600 IU is produced in summer sunlight in less than one minute in a light skinned individual. If God or nature created a system that produces such a vast quantity of D, there is a reason for it, and it is obvious that 5,000 IU per day is not harmful. Dr. Reinhold Vieth has presented compelling information that there is no evidence of any toxicity or adverse effects at prolonged intakes of 10,000 IU per day (Vieth, R Ann Epidemiol;2009;19:441-5).
5. The IOM also inexplicably recommended the same vitamin D intake for infants as for adults (600 IU), which to any reasonable person, is illogical.
6. The IOM used only bone health to make its recommendations, but bone health is a terrible indicator of adequate vitamin D levels because only very small quantities of vitamin D are adequate to ensure bone health. The IOM, by ignoring both observational and randomized controlled trials showing that low levels of vitamin D correlate to a multitude of health problems including cancer, heart disease, depression, influenza, Multiple Sclerosis, and autism, has done a dreadful disservice to those struggling with these and other health issues that are impacted by low vitamin D levels.
7. Ironically, the IOM consulted with several leading vitamin D researchers but then completely ignored their recommendations. This indicates a bias that may extend beyond simple ignorance and descend into the realm of concealing information.
Another of the most prolific researchers in the vitamin D field, Dr. William Grant, gave the Sunlight Institute this statement regarding his feelings about the IOM report:
“The Dietary Reference Intakes for Vitamin D and Calcium committee of the Institute of Medicine of the National Academies was essentially a tool of the agencies that funded the study, including the Food and Drug Administration and the National Institutes of Health. Federal sponsors defined the key questions, and a technical expert panel was assembled to refine the questions and establish inclusion and exclusion criteria for the studies to be reviewed. By excluding ecological studies and case-control studies in which serum 25(OH)D levels were measured at time of diagnosis, they in essence dictated the conclusion that vitamin D has no health benefits other than for healthy bones. Since 90% of our vitamin D comes from the sun, they throw out 90% of the evidence. The work of this committee contrasts with well-conducted scientific reviews such as that by the Intergovernmental Panel on Climate Change, which included over 600 scientists contributing to the report and 500 scientists as reviewers. The process was open rather than behind closed doors and resulted in a Nobel Prize for the contributors. If only health policy were treated as a science instead of a business tool.” William B. Grant, Sunlight, Nutrition and Health Research Center (SUNARC), San Francisco
In putting forth its report, the IOM has destroyed any credibility it might have had with those who conduct the science of vitamin D. The IOM has misled the public and placed itself on a level with those who, in the past, ignorantly told us to avoid sunlight exposure at all costs. If the public follows their recommendations we will return to the Dark Ages of health awareness; the report is an absurd suppression of critically important research.
A new study from France has shown that women who were exposed to a combination of sunlight and dietary vitamin D had up to a 45% reduced risk of contracting breast cancer (BC). The researchers noted that “high” dietary vitamin D by itself did not correlate to a reduced risk of BC, whereas sunlight exposure alone did correlate to a lowered risk.
This research should come as no surprise, since there is a miniscule amount of vitamin D in the typical diet. For instance, the typical 3 ½-oz piece of farmed salmon contains about 175 International Units (IU) of vitamin D; 8 oz. of fortified milk 100 IU; 8 oz. fortified orange juice 100 IU. The amounts typically derived from eggs, oils and margarine is negligible. It is now felt by many experts in the vitamin D field that 4,000-5,000 IU of vitamin D supplementation is necessary for optimal health, so it can be seen that trying to optimize breast health with the paltry 400-500 IU from diet is like trying to color the ocean red with a cup of tomato paste.
Conversely, 20 minutes full-body exposure to summer sunlight at noon can produce as much as 20,000 IU; so this study, showing that sunlight correlates far better to lowered BC risk than does dietary vitamin D, would be expected. However, most people are not actively seeking the sunlight and are not even close to producing the 20,000 IU mentioned. Therefore, in this French BC study, it was probably the combination of both sunlight-produced vitamin D and dietary vitamin D that sufficiently increased blood levels to a threshold that triggered vitamin D’s cancer protection mechanisms, which are numerous.
Other research—a double blind, placebo controlled interventional study—has shown that when vitamin D supplementation is over 1,100 IU daily, there is a profound correlation to a lowered risk (from 60-77%)of all cancers in women.
And as to sunlight per se, Dr. Esther John and colleagues conducted research on the sun-exposure habits of women and correlated those habits to the risk of developing BC. Those women who had the greatest exposure to sunlight were 65% less likely to develop BC.
After the Institute of Medicine (IOM) made their inanely low recommendations for vitamin D supplementation (600 IU daily for all ages), it is good to see that research belying that foolishness continues to surface. We must remember that sunlight exposure is the most natural way to produce vitamin D, and that if supplements are going to be used when sunlight is not available, a minimum of 2,000-4000 IU daily is necessary to optimize blood levels for best health.
 Engel P, Fagherazzi G, Mesrine S, Boutron-Ruault MC, Clavel-Chapelon F. Joint effects of dietary vitamin D and sun exposure on breast cancer risk: results from the French E3N cohort. Cancer Epidemiol Biomarkers Prev 2010 Dec 2. [Epub ahead of print]
 Hollis BW. J Nutr 2005;135:317-22
 Lappe J, Travers-Gustafson D, Davies M, Recker R, Heaney R. Vitamin
D and calcium supplementation reduces cancer risk: results of a randomized trial. Am J Clin Nutr 2007;85:1586 –91.  John, E. et al. Vitamin D and breast cancer risk: The HANES 1 epidemiologic follow-up study, 1971-1975 to 1992. Cancer Epidemiology Biomarkers and Prevention 1999;8:399-406.
By: Mike Swain December 17, 2010–
Braving the midday sun is not such a crazy thing to do after all – in Britain.
In fact, it could be the best time to soak up the rays so that your body gets enough vitamin D for healthy bones.
Contrary to the cover-up message in Noel Coward’s famous song, Mad Dogs and Englishmen, experts reckon that some unprotected sun exposure around noon is vital to health.
Seven leading health groups and charities recommend up to 15 minutes of bare skin exposure three times a week in summer. And midday is best.
Before 10am and after 4pm the rays are too weak in the UK even in summer to stimulate vitamin D synthesis in the skin.
But they stress that people should “never be red” at the end of the day as sunburn could lead to skin cancer. After 15 minutes it is time to go in, cover up or slap on sunscreen.
The guidance hopes to make it clear that “little and frequent” sun exposure is a good thing and that it is important to strike a balance between adequate vitamin D and avoiding skin cancer.
Professor Rona Mackie, of the British Association of Dermatologists, said: “Some of the messages about sunbathing have been a bit too negative. UK sunshine is not desperately strong.
“Exposing your face, arms and legs three times a week will do no harm.
“But your skin should not look as if it has been in the sun all day.”
And in the dark days of winter she advises keeping up vitamin D levels with “a holiday to the Canaries”.
By Richard Gray–
Researchers studying how sun exposure affects the risk of developing melanomas discovered that those who spent between four to five hours in the sun each day over the weekend were less likely to develop tumours.
The findings appear to contradict the commonly-held belief that longer time spent in the sun increases the risk of skin cancer.
Instead, the study shows that while excessive exposure to the sun – and particularly sunburn – can lead to melanomas, regular doses of sun for up to five hours a day at weekends can be protective.
The study comes just days after Andy Flowers, the England Cricket team head coach, underwent surgery to remove a malignant melanoma below his right eye.
Professor Julia Newton Bishop, an epidemiologist who led the research at Leeds University, said it seems regular exposure helps the skin adapt and protect itself against the harmful affects of sunshine. Increased levels of vitamin D made in the skin while exposed to sunlight may also be protective.
Professor Newton Bishop said: “The relationship between the amount of sun we are exposed to and the risk of melanoma is complicated – we have known for a long time that melanomas are something to do with sun exposure and fair skin.
“Our paper suggests that moderate regular sun exposure may actually reduce the risk. We are talking about quite high levels of sun exposure for the protective effect with an average of four to five hours a day at weekends.
“It appears that in moderation, sun exposure can be protective, but it is when you have extreme sun exposure that it becomes a problem. So in the UK sunburn is a potent risk factor because we have a habit of not getting much sun at home and then suddenly exposing our skin when we go abroad.”
Malignant melanoma is the most serious type of skin cancer and around 10,000 people in the UK are diagnosed with the disease each year. The incidence of the disease is rising faster than any other cancer in the UK and has quadrupled since then 1970s. Around 2,000 die each year in this country from skin cancer.
Public health experts blame the rise in skin cancer in the UK on growing use of sun beds and an increase in the number of holidays people take abroad.
Harmful ultraviolet light from the sun is thought to trigger skin cancer by causing damage to the DNA in the skin.
But the new study by Professor Newton Bishop and her colleagues, which is published in the European Journal of Cancer, suggests that regular sun exposure can help the body prevent this damage.
The researchers examined the sun exposure behaviour and skin type of 960 melanoma patients and 687 controls who had not been diagnosed with skin cancer.
After adjusting the results to account for deprivation, they found that participants with fair skin, freckles and blonde or red hair, were most at risk of developing melanomas as where those who had suffered severe sunburn.
But they also found that regular exposure to the sun at weekends of more than five hours had the most significant effect that protected the participants from developing melanoma.
Unfortunately for those with sensitive skin, this protective effect was not seen in people who had red hair and freckles, perhaps due to their tendency to burn far more quickly.
The researchers also measured levels of vitamin D in 1,167 of the participants, who were aged between 18 and 76 years old, and found that those who received regular doses of sun exposure at weekends also had raised levels of vitamin D.
Professor Newton Bishop said: “There is some evidence from other studies that suggests that vitamin D may help to reduce melanoma size and improve prognosis, but it could be that there is some adaptation going on in the skin which reduces the damage from ultraviolet light.
“Melanoma, in the UK, is a cancer of people who work inside who have short bursts of sunshine when they are on holiday. If they are working in offices all week, then when they go sunbathing on holiday, they don’t have the protection that might naturally develop.
“Regardless, people need to take steps to avoid getting sunburnt – particularly at this time of year when the days are shorter and there is much less sunshine around. People who go away for winter sun holidays are particularly at risk.”
By: Peter Vinthagen Simpson December 2, 2010–
“Our studies show that women with active sunbathing habits live longer,” said chief physician Håkan Olsson at the division of oncology at Lund University, to the local Göteborgs-Posten (GP) daily.
Studies of the sun exposure habits of 40,000 women in southern Sweden have found that the health benefits of spending extended periods in the sun outweigh the negatives, such as the increased risk for skin cancer.
Olsson argued that he was not alone in claiming “that there can be other factors other than the sun which affect the risks for developing malignant melanomas”, and that exposure to the sun could help protect against a slew of other conditions.
Researchers claim that exposure to the sun is attributed to helping against blood clots, which are twice as common in the darker periods of the year than in the summer, the newspaper reported.
Furthermore the incidence of type 2 diabetes also shows seasonal variations, with the winter boom in cases attributed to a lack of vitamin D.
Skin cancer is however an increasing problem in Sweden, including the occurrence of dangerous malignant melanomas and the role of vitamin D is becoming an increasing popular cancer research area as scientific evidence mounts of its positive health benefits.
While doctors agree that avoiding sunburn and exercising caution in the sun is important, there is some dissent over blanket recommendations against solariums, protective clothing and comprehensive use of sunscreen, GP reported.
“We know that we are inside much more than before – this is certainly a factor to the declining levels of vitamin D,” Håkan Olsson told the newspaper.