Maybe you are one of the shade seekers. You moisturize with SPF 15 face cream, no matter what the season. You avoid the sun, spending the peak-light hours indoors. When you do venture out, you’re never without a wide-brimmed hat and long sleeves. From the sunscreen in your lip balm to your wraparound sunglasses, you’ve taken every precaution to avoid hazardous ultraviolet rays. With any luck you’ll successfully stave off skin cancer — and maybe even dodge a wrinkle or two. But could you be courting other health dangers? Perhaps. It’s becoming clear that getting just the right amount of sun is a rather delicate balancing act.
For years dermatologists have warned of the hazards posed by sun exposure, noting that excessive amounts, especially if they lead to sunburn, can lead to premature aging and even skin cancer. This year alone, more than a million Americans will develop skin cancer from long-term exposure and bad sunburns — more new cases than all other cancers combined. More than 90 percent of all skin cancers occur on parts of the body exposed to the sun: the face, neck, ears, forearms, chest, back, legs and hands. The three most common types are basal cell carcinoma — which accounts for more than 70 percent of all skin cancer cases, but which has a high cure rate when diagnosed and treated early — followed by the more deadly ones, squamous cell carcinoma and malignant melanoma. In fact, melanoma alone accounts for approximately 75 percent of all skin cancer deaths.
Yet even now, well into the second decade of double-digit SPFs, a number of researchers and medical experts have begun to question the strategy of total sun avoidance. Their message: Avoiding and blocking out the sun too assiduously might deprive you of the sun’s life-sustaining benefits, which are significant. A lack of sunlight can put you at risk of a vitamin-D deficiency, among other things, and increase your susceptibility to a number of diseases, including life-threatening cancers.
Rather than simply viewing the sun as a health danger, some experts are now encouraging us to consider the important advantages that the sun’s light and energy — in measured amounts — have to offer.
Light and Dark Cycles
Electromagnetic energy is probably the last thing on your mind as you step out on a summer morning, but it’s all around you, sustaining you on a number of levels. From 93 million miles away, the nearest star showers the earth with energy of varying wavelengths and frequency — from gamma rays on one end of the spectrum to radio waves on the other. At the center of this continuum lies visible light, energy with a big impact on human health and happiness.
The fact that sunshine makes you feel good is, of course, wonderfully self-evident. There’s nothing like a bright, warm day to lift the spirits. But the inner workings of this pleasurable feeling are actually quite complex. The sun’s most obvious benefit — visible light — strongly influences hormones, which in turn affect your sense of well-being.
Hormones that regulate everything from appetite and sleep to your immune system all depend on daylight for cues. “The amount of light that hits you [tells your body] when to eat, what to eat and when to reproduce,” explain researchers T. S. Wiley, PhD, and Bent Formby, PhD, authors of Lights Out: Sleep, Sugar, and Survival (Atria, 2001). “Light-and-dark cycles turn hormone production on and off, activate your immune system, and time neurotransmitter release daily, and especially seasonally.”
For example, your levels of dopamine, the neurotransmitter associated with feelings of pleasure, respond to the amounts of visible light your eyes take in, as do prolactin and melatonin, which govern the immune system. Your desire for food (and certain kinds of foods) stems from circadian cues informed by the angle of sunlight and length of day. The summer’s long daytime hours, for instance, prompt us to crave carbohydrates in preparation for winter’s historically short food supply. (For more on circadian rhythms and light, see “Light Rhythms” in the June 2009 archives.)
And then there’s sleep. The pineal gland, located at the center of the brain, secretes melatonin, a hormone that regulates slumber. Melatonin is suppressed by light, so when you’re out and about on a sunny day, its production decreases. When the sun sets, melatonin levels rise so you can sleep.
But when we aren’t exposed to adequate light, either because we are avoiding it as a matter of course or because, as in winter, there simply aren’t many hours of sunlight available, the operation of our pineal glands can become suppressed. That’s a phenomenon many of us have experienced firsthand. About 5 percent of Americans experience seasonal affective disorder (SAD) — a condition characterized by winter-month sleeplessness and depression — while another 10 to 20 percent endure mild symptoms, according to the American Academy of Family Physicians.
The common cure for SAD aims to compensate for the lack of sun with a bright lamp that suppresses melatonin production. But the method doesn’t work for everyone, and it seems nothing compares to the real thing: The National Mental Health Association suggests spending more time outdoors to relieve mild SAD symptoms and points to a study showing that walking for an hour outdoors in the winter sun works just as well as sitting for more than twice that time in front of a specialized lamp.
The UV Dilemma
With its sunny influence on moods and well-being, visible light doesn’t elicit much controversy. It presents a problem only in its absence: When you don’t get enough from the sun, as in winter, the resulting melatonin excess can dampen your disposition. But the case of ultraviolet (UV) light poses a more contentious issue. We know that too much exposure causes skin cancer, yet a growing body of research suggests that getting too little may present an even greater threat.
Before its skin-cancer effect was fully known, the sun’s light — visible and UV — had quite a favorable reputation. In the late 19th century, Danish scientist Niels Finsen’s therapeutic use of ultraviolet light broadened the knowledge about the sun already established during that period — namely that sunlight could prevent the growth of bacteria and give a boost to overall health. His research, along with that of others who sought to quantify the sun’s effects, gave rise to the field of heliotherapy (“helio” is Greek for “sun”), which uses the sun for general healing, and phototherapy, which employs ultraviolet light or infrared radiation for specific medical purposes. At a time when fashion favored pale skin, the medical community viewed sunlight as a valuable tool.
Fast-forward to the mid-20th century, when the link between the sun and skin problems became apparent, bringing about the demise of unprotected sunbathing. High-intensity sunscreens emerged in the 1980s, and their use has increased ever since. But new research has cast the long-vilified UV (in its two wavelengths: UVA and UVB) in a different light. Studies now suggest that the sun may play a protective role on many health fronts, from cancer to osteoporosis to autoimmune conditions. The reason? We now know that vitamin D influences all of these conditions and that the sun, more than food or supplementation, is the body’s best source for obtaining it.
“Ninety to 95 percent of our vitamin D is made in the skin with ultraviolet B energy from the sun and transformed in the body,” explains Michael Holick, PhD, MD, a Boston University professor of medicine, physiology and biophysics, and director of the Bone Health Care Clinic. One main function of this vitamin is to regulate the body’s absorption of calcium — hence the addition of vitamin D to milk and some juices, yogurts and cereals. After skin is exposed to the sun, the vitamin enters the blood, travels to the liver to be synthesized to 25-hydroxyvitamin D, then to the kidneys, which converts it to an active form: 1,25-dihydroxyvitamin D. Finally, it winds up in the intestine, where it helps the body absorb dietary calcium.
The calcium connection makes plain the link between vitamin-D deficiency and bone-related disorders. The National Institutes of Health cites osteoporosis among the most serious dangers of not getting enough vitamin D. In one 1999 study, published in the Journal of the American Medical Association, one-half of women with osteoporosis who were hospitalized for hip fracture at Brigham and Women’s Hospital in Boston also were vitamin-D deficient. Another more recent study in Australia came upon a similar finding: Of 1,500 elderly women, the higher the vitamin-D levels, the less likely they were to suffer a bone-breaking fall.
Meanwhile, rickets, a vitamin-D-deficiency disease that prevents proper bone formation in childhood, has recently resurfaced as a public health issue — possibly, some speculate, because of decreased exposure to sunlight. In response to this, the American Academy of Pediatrics issued a recommendation in 2003 that all infants — particularly those who are breastfed, since breast milk is naturally lower in vitamin D compared with formula — receive 200 IU of vitamin D supplementation daily.
But the benefits of this nutrient are more than bone deep. “Low vitamin-D states are also associated with cancer, heart disease, diabetes, hypertension, weak immune systems, chronic pain, and autoimmune diseases, such as multiple sclerosis,” says Gregory Plotnikoff, MD, MTS, FACC, medical director of the Penny George Institute for Health and Healing in Minneapolis. “Vitamin D is actually a potent hormone that regulates at least 600 different genes associated with key functions. When not enough vitamin D is present, disease may be present.”
In 2003, Plotnikoff even found a strong link between vitamin-D deficiency and pain. In his study of 150 people with unexplained bone and muscle pain, 93 percent had too-low levels of vitamin D. (Five of them actually had undetectable levels.) “All five were frequent clinic visitors with multiple complaints that were attributed to either mental health issues or were deemed to require invasive procedures,” he explains, suggesting that this vitamin deficiency may be a silent contributor to other health ills.
Of all the low-D-related problems, however, cancer comes as the biggest surprise — and, ironically, provides another reason why you should think twice about the wisdom of total sun avoidance.
Holick points, for instance, to research conducted in Scandinavia, where scientists studied two groups of men with prostate cancer: one whose members had been continually exposed to the sun through their outdoor occupations, and one whose members had worked indoors. “Those who worked indoors got prostate cancer at the average age of 52. Those who worked outside didn’t get the disease for another three to five years after that,” he says. A recent study in Canada revealed that teenage girls and young women exposed to the most sunlight had a reduced risk of breast cancer by more than 50 percent.
It’s this type of disparity that led Holick to question whether the kidneys alone are the sole manufacturers of active vitamin D. He and his colleagues eventually discovered that they aren’t. Many types of cells, including breast, colon and, as suggested above, prostate, can activate the vitamin.
This clue hints at the possibility that several types of cancer may have a vitamin-D component. The National Institutes of Health acknowledges possible evidence that the vitamin “may be protective against some cancers,” including colon cancer.
Holick is less tentative: “Increasing vitamin-D levels in our bloodstream via sun exposure or supplements — and, to a lesser extent, diet — will help lower the risk of several diseases, especially those caused by abnormal cell growth, such as cancer,” he notes in his book, The UV Advantage (ibooks, 2004), coauthored with Mark Jenkins.
Sizing Up the Sun
Of course, despite the long and growing list of sun benefits, the simple fact remains: Too much UV exposure causes skin cancer, a problem that dermatologists still emphasize strenuously, perhaps now more than ever. New concerns over the pitfalls of sun avoidance may have piqued the interest of some in the medical field, but those who treat skin cancer on a daily basis remain largely unconvinced. “There’s just no data to support that covering up in the sun causes health problems, and there’s plenty of clinical trials to show that it doesn’t,” argues Darrell Rigel, MD, clinical professor at New York University Medical Center and a physician at NYU Tisch Hospital. He joins a host of other dermatologists who don’t dispute the studies showing the consequences of vitamin-D deficiency — just the idea that practicing “safe sun” is to blame.
“I keep hearing about how we need to spend unprotected time in the sun. We don’t. We can get vitamin D in other ways,” says Rigel. “One in five Americans will get skin cancer in their lifetime. It’s one of the few cancers for which we know the cause, and a simple behavioral change [sun protection] greatly reduces your risk.”
To prove his case, he points to those people at the extreme end of sun sensitivity, whose xeroderma pigmentosum (a rare genetic defect) renders them so sun-sensitive that they completely avoid ultraviolet light. “One would think they’d have correspondingly low vitamin-D levels. They don’t,” says Rigel. The condition, he argues, doesn’t make them any more vitamin-D deficient than those without the UV sensitivity. He also stresses that in the cases of SAD, PMS and other psychophysical conditions that respond well to sunshine, the key is visible light, not UV. Sunscreen doesn’t block the body’s ability to derive circadian cues from daylight, he adds.
Rigel says people can get enough vitamin D from brief moments of unprotected sun during the day, as well as through diet. But Holick disagrees. Dietary forms of vitamin D exist, he acknowledges, such as certain fish and fortified milk and juice, but you’d have to eat 3.5 ounces of mackerel or salmon three to four times a week, or drink 10 glasses of fortified orange juice or milk daily to get your share.
It’s easy to find a vitamin-D-only supplement, but Holick cautions against doubling up your multivitamin, as this would result in too-high doses of other vitamins like A, which increase risk of osteoporosis.
So that leaves the sun and some supplements. But you don’t have to get a lot of rays in order to load up on vitamin D, says Holick, “If you go out in a bathing suit and your skin turns a light pink, you’ve made about 20,000 IU of vitamin D. That’s 50 to 100 times the recommended daily amount you need.”
Clearly, it isn’t necessary to turn the least bit pink to get one’s share of the sun’s healthy benefits: For vitamin D, at least, the briefest of sunbaths is likely to do the trick.
Moderation in All Things
The average person may feel faced with a choice between “two evils”: skin cancer on the one hand or multiple health ills on the other. Not so, says Holick. Because the skin makes vitamin D so well, you need only a small amount of sun — about 10 unprotected minutes on the arms and legs between 10 a.m. and 3 p.m. depending on the latitude, your skin pigment and the season, followed by good sun protection, three times a week.
For all the quibbles among experts about how much sun we should get, one thing is certain: Nobody suggests roasting on the beach for hours slathered in baby oil. The dangers are just too great.
The point is (at least according to many experts), you needn’t face an all-or-nothing choice. “The risk of (some) cancers appears to be far higher from inadequate sun exposure than from routine sun exposure,” says Plotnikoff, who recommends most Midwesterners take at least 1,000 IU of vitamin D3 a day.
Plotnikoff, like many experts in the middle camp, suggests taking precautions in accordance with your family’s skin-cancer history and your own skin type. Do what you can to avoid excessive exposure and burns, they advise, but don’t be afraid to enjoy the sun in moderation. When you do turn your face to the sunshine, do so with the comfort and satisfaction of knowing that getting a little of that warm glow can actually do you a whole lot of good.