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.”
If this vitamin isn’t in your medicine cabinet, it probably should be.
By Linda B. White, M.D.
What do the following conditions have in common: osteoporosis, multiple sclerosis, high blood pressure, diabetes and cancer? Give up? Experts suspect that insufficient levels of vitamin D raise your risk of getting these diseases. Unfortunately, most of us probably are vitamin D deficient.
About all I was taught in medical school is that vitamin D keeps bones strong. Recently however, this area of study has exploded as scientists uncover the vitamin’s far-reaching effects. Because it increases calcium levels, vitamin D indirectly fortifies bones and teeth. It also regulates cells all over the body, which explains vitamin D’s disparate roles, such as influencing insulin production and immune function, as well as helping prevent inflammation and cancer.
The scary thing is that vitamin D deficiency appears to be quite common. A recent British study found that 87 percent of volunteers had low blood levels of the vitamin in winter and spring, and 61 percent had low levels in summer and fall. Why the seasonal variation? Our chief source of vitamin D is sunshine.
Why We’re D-ficient
In response to ultraviolet B (UVB) rays in sunlight, our skin transforms a derivative of cholesterol normally found in the skin into vitamin D3 (cholecaliferol). The liver, kidneys and other tissues further activate this molecule. Given that the skin is a veritable vitamin D factory, why is deficiency so rampant? History — ancient and recent — holds the answers.
Humans evolved near the equator and spent days outdoors, allowing the skin to generate ample amounts of this vitamin. About 50,000 years ago, some of our ancestors migrated toward the poles, where winter sunlight isn’t intense enough for vitamin D production. However, their diet of vitamin D-rich fish compensated for the deficit.
But rickets became prevalent in the 18th century during the Industrial Revolution, when people shifted to indoor labor and the skies darkened with pollution. This manifestation of severe vitamin D deficiency causes skeletal deformities, such as bowed or knocked knees and bony knobs along the ribs, known as rachitic rosary. During the 1930s, the decision to add vitamin D to milk nearly eradicated rickets in the United States. But nowadays, kids and adults drink less milk and more juice and sodas, and sadly, rickets is making a comeback in American children according to a study released last year.
Starting about 30 years ago, another cultural shift deepened our vitamin D deficit: public health campaigns to avoid the midday sun, cover up and apply sunscreen. They were justified attempts to save our skins from sun-induced aging and cancer, but now we’re not making enough vitamin D. These days, vitamin D deficiency has become commonplace, even in the tropics. For instance, a sampling of adults in sunny Honolulu showed that half were low in D.
Of course, we can take supplements, but current government recommendations are cautious — 200 IU a day for young adults, 400 for people 51 to 70, and 600 for those over 70. Vitamin D expert Bruce W. Hollis, M.D., of the Medical University of South Carolina, says such doses might be enough to prevent rickets, but aren’t sufficient to fulfill other important functions.
Most of us don’t even meet these inadequate guidelines. A German study found that 80 percent of sampled adults didn’t get recommended amounts, and nearly 60 percent had low blood levels of vitamin D, a statistic that rose to 75 percent in women over 65 years old. Furthermore, those women with low blood levels of vitamin D were more likely to have high blood pressure, cardiovascular disease and type 2 diabetes.
Results of D-ficiency
So what are the dangers of too little vitamin D in your system? A whole host of chronic conditions.
Weak bones and muscles. Rickets was the first disease tied to vitamin D depletion. This severe deficiency during childhood can prevent kids from reaching their potential for full height and peak bone mass. (Bone mass peaks in early adulthood; after that it slowly declines.)
In adults, vitamin D deficiency can lead to osteoporosis (thin, brittle bones) and osteomalacia (rubbery, demineralized bones). The latter causes bone pain, and both elevate the risk of broken bones.
Additionally, vitamin D deficiency causes muscle weakness and discomfort. One study found that patients with aches and weakness were often severely vitamin D deficient. Hollis says he’s hearing from doctors that vitamin D supplementation often resolves these aches and pains, adding, “A lot of ‘fibromyalgia’ is probably D deficiency.”
Weakened muscles increase the risk of falls and fractures — a dangerous combination for the elderly. The research shows that, although the recommended dose of 600 IU a day doesn’t prevent falls and fractures in older adults, doses over 800 IU do. In fact, consuming 700 to 800 IU of vitamin D a day (plus or minus calcium) could prevent a quarter of hip fractures in older people, according to a study published in the Journal of the American Medical Association.
Cancer. Vitamin D deficiency has been linked to several types of cancer, including breast, prostate, colon and melanoma. In fact, for more than 60 years, research has found that people living at higher latitudes with less exposure to sunlight showed an increased risk of cancer mortality. Adequate vitamin D levels seem to protect against some cancers. In a recent study, researchers followed healthy postmenopausal women whom they assigned to take either 1,400 to 1,500 milligrams a day of supplemental calcium plus 1,100 IU a day of vitamin D3, or a placebo for four years. After the first year, vitamin D supplementation led to a 57 percent reduction in cancer.
Cardiovascular disease. In addition to cancer and bone disease, vitamin D may also be healthy for your heart. Vitamin D levels are inversely associated with the risk of high blood pressure and congestive heart failure. Exposing people with high blood pressure to ultraviolet light has been shown to improve the condition.
Asthma. Preliminary studies show that vitamin D also may help alleviate respiratory problems, such as asthma. According to one study published in the American Journal of Clinical Nutrition, children of mothers with lower intakes of vitamin D during pregnancy are more likely to develop asthma.
Autoimmune disorders. Vitamin D reduces inflammation and plays a role in the maturation of the immune system. Deficiency is common in autoimmune diseases where the immune system attacks normal cells, such as type 1 diabetes, rheumatoid arthritis and multiple sclerosis (MS). Emerging research shows that vitamin D may have a preventive effect. One study examined two large groups of women for 10 years and found a reduced risk of MS was associated with vitamin D supplementation. A study of Finnish children taking 2,000 IU a day (10 times the current recommendation) showed they had a decreased risk of developing type l diabetes. In an analysis of the Iowa Women’s Health Study, women consuming higher levels of vitamin D showed a reduced risk for rheumatoid arthritis.
Mental health. Psychiatrist John Cannell, M.D., founder of the nonprofit Vitamin D Council, says that vitamin D may contribute to several emotional disorders. In a study of elderly people, mood and cognitive skills deteriorated with lower levels of D. Cannell points out that seasonal affective disorder (SAD) is a type of depression whose onset follows the waning daylight of autumn and winter. An Australian study found that vitamin D supplements lifted the mood of people with SAD.
How to Get Enough D
Expose yourself. Your skin can tackle much of your vitamin D needs. If you’re young, fair, scantily clad and near the equator, 10 to 15 minutes of peak sunshine produces 20,000 IUs.
However, Hollis says a dark-skinned person requires 10 times that exposure to make an equivalent amount of D. And a 70-year-old person makes only a quarter of the vitamin D that a 20-year-old can produce. During the fall and winter in higher latitudes (above 37 degrees latitude — San Francisco is just above 37 degrees), the levels of UVB fall below the threshold needed for even a fair-skinned person to produce enough vitamin D. Additionally, complete cloud coverage cuts UV energy in half, and shade reduces it by 60 percent.
Sunscreens also block UVB waves, the wavelength that stimulates the skin’s vitamin D production. According to Michael F. Holick, M.D., Ph.D., of the Boston University School of Medicine, a sunblock with SPF 8 reduces the skin’s vitamin D production by 95 percent. “If you wear sunscreen ‘properly,’ you’ll become vitamin D deficient,” he says.
But what about skin cancer? Despite increased sunscreen usage, skin cancer rates have risen. One reason is that, until recently, sunscreens didn’t impede deeply penetrating UVA light, and presumably, our false sense of security led to more time in the sun and an increase in skin cancer.
What should you do? “Be sensible,” Holick advises. “Know your own skin sensitivity.” For instance, if you turn pink after 30 minutes in the summer sun, thenspending five to 10 minutes (in a bathing suit) in the sun should generate plenty of vitamin D. After that, apply sunscreen, cover up and seek shade.
Eat D-licious foods. Only a few foods contain much vitamin D. Sources of vitamin D include cod liver oil (1,360 IU per tablespoon); oily fish such as salmon, sardines and mackerel (about 350 IU per 3.5 ounces); eggs (about 20 IU per yolk); and fortified milk, soy milk and orange juice (98 IU per 8-ounce serving). (We’re testing pasture-raised chicken eggs for vitamin D as part of our 2007 egg testing project. See October/November 2007 for the initial results. — Mother)
Shiitake mushrooms can be an exceptional source of vitamin D, as noted in research published in Paul Stamets’ book, Mycelium Running. Shiitake mushrooms grown and dried indoors have only 110 IU of vitamin D per 100 grams. But when the shiitakes were dried in the sun, the vitamin D content rose to 21,400 IUs per 100 grams. Even more surprising, when the mushrooms were dried with their gills facing up toward the sun, their content rose to 46,000 IU!
Take supplemental D. Most North Americans can’t maintain healthy blood levels of D from sunlight and good diet. Therefore, many experts recommend 800 to 1,000 IU a day — several times the government guidelines of 200 to 600 IU.
The exact amount depends upon several things. If you’re dark-skinned or spend little time outdoors, you’ll obviously need more than a Caucasian lifeguard. And if you’re already deficient in vitamin D, you’ll need hefty doses just to get your blood levels up to normal.
If you’re pregnant or nursing, you’ll also need more. Hollis and colleagues are currently researching the effects of different vitamin D doses in pregnant women of various races. Until the results of that trial are finalized, he can’t recommend more than 2,000 IU per day.
When asked how much vitamin D they normally take, Hollis says he takes 4,000 IU a day, while Holick says each member of his family takes 1,000 IU of D3 a day. Holick also spends reasonable amounts of time outdoors.
Be aware that many supplements provide vitamin D as ergocalciferol (vitamin D2), rather than cholecalciferol (vitamin D3). D3 is the form naturally occurring in our bodies and is more effective.
No one really knows how much vitamin D might be too much; however, toxicity is exceedingly rare. The Food and Nutrition Board sets the upper level for daily dietary intake at 2,000 IU, though Hollis thinks that’s not enough to maintain health at northern latitudes. Accumulated research demonstrates 10,000 IU of vitamin D3 to be a more realistic upper limit.
Who’s at Risk?
The only way to measure vitamin D blood levels is to check a form of vitamin D called 25-hydroxyvitamin D. Doctors don’t routinely perform this test, and Holick thinks universal screening would be too expensive. If you’re at risk for, or already have symptoms of, deficiency, then you might want the blood test.
Just who’s at risk? Research shows the following populations face greater risk of vitamin D deficiency:
Dark-skinned people. Melanin darkens skin and absorbs UV light, which protects against sun damage and limits vitamin D production. Holick’s research shows that 80 percent of African-Americans studied in Boston over age 65 were vitamin D deficient — at the end of summer!
Northerners. People who live at higher latitudes where winters are long and dark run a higher risk of vitamin D deficiency. Holick notes that even fair-skinned people living above 37 degrees latitude make little vitamin D during the winter.
Older adults. The skin production of vitamin D and its activation in the kidneys declines with age. Further, the elderly typically spend more time indoors. Vitamin D deficiency in this age group contributes to osteoporosis and falls.
Breast-fed infants. Research in Iowa by Hollis and colleagues found that vitamin D deficiency, including severe deficiency, was common among breast-fed infants without vitamin D supplementation. Vitamin D deficiency in nursing mothers is the reason breast milk is D deficient. Unfortunately, early deficiency can have lifelong consequences.
People with intestinal disorders. Disorders that interfere with fat absorption include celiac disease, Crohn’s disease, pancreatic insufficiency, liver disease or cystic fibrosis. Fat-soluble vitamins such as D are absorbed from the intestine with dietary fat, so people with low ability to absorb fat may need vitamin D supplements.
Sun avoiders. People who cover up for religious, cultural or health reasons also run the risk of deficiency. Clothing blocks UVB waves, interfering with or preventing the skin’s formation of vitamin D.
The obese. In a British study, obese people were twice as likely as those of normal weight to be low in vitamin D. Hollis explains it’s because fat sponges up vitamin D and stores it, but doesn’t release it.