Wearing sunscreen and avoiding excessive sun exposure are still key to preventing skin cancer, but what you eat may also help save your skin from basal- and squamous-cell carcinomas, the two most common types of skin cancer. The incidence of these so-called nonmelanoma skin cancers has been rising dramatically for the past 20 years, especially among those under age 30. According to both animal and human studies at Baylor College of Medicine in Houston, the amount of fat consumed has a direct effect on the development of these tumors. “A high-fat diet seems to shorten the length of time between the damaging UV exposure and the appearance of skin cancer, and it also increases the number of tumors that develop,” says study coauthor John Wolf. M.D.. professor and chairman of the department of dermatology at Baylor.
High levels of dietary fat do not cause skin cancer, but they appear to affect the promotion/progression phase of cancer development. In animal studies, the Baylor researchers have demonstrated that when a low-fat diet is fed to animals immediately after a carcinogenic dose of ultraviolet light, the aggravating effects of the high-fat diet previously consumed are negated. Dr. Wolf expects to find a dietary link when the Baylor human study concludes this year; already the study has shown a significant decrease in the number of precancerous skin growths in volunteers on a low-fat diet. “Ultimately it means we may be able to intervene with diet to prevent skin cancers despite a person’s previous sun-exposure history,” he says. And it means that following a low-fat diet (no more than 20 percent of daily calories coming from fats) along with wearing sunscreen may dramatically decrease the incidence of skin cancers.
The right clothes can shelter you from the sun, but you have to pick and choose carefully. New research from the Morehouse School of Medicine in Atlanta shows that some T-shirts and polo shirts moy not adequately protect against solar UV and skin cancer. In the study, three groups of mice were exposed to UV light-one group was left unshielded, another was shielded by a typical shirt fabric and a third was shielded by a high SPF fabric. After 12 weeks, mice in the first two groups had multiple skin cancers while those shielded by the high SPF fabric hod no cancers or even precancers. “Wearing a T-shirt without sunscreen underneath could leove you vulnerable to sun damage,” says study director Julian Menter, Ph.D. Clothes with labeled SPFs are now available from Solumbra by Sun Precautions, but a lot of fabrics have naturally high SPFs. What to consider:
• Fiber content Both natural and synthetic fibers have a wide range of solar protection: According to Madhu Pathak, M.D., of Harvard University, high SPF acrylics include closely knitted Orion, Acrylon and Contrelle (rayon is not as protective); medium to low (SPF 10 to 30) natural fibers include silk and cotton.
Underwater but not undercover Ultraviolet light can penetrate up to three feet through water.
Gauging sun intensity
Personal UV monitors (like the new SunWatch II or SunCast) and the UV Index that’s broadcast and televised in 58 cities nationwide make it easy to tell how intense the sun is and how much protection you need before going outdoors. But there are also easy gauges that can clue you in to the sun’s intensity.
Shadow length When your shadow is longer than you are tall, the sun is lower in the sky and is thus less intense.
The sun must beam through more of the earth’s atmosphere, which filters more ultraviolet rays. When your shadow is shorter than you are tall, the sun is overhead and most intense, causing the highest sunburn potential.
• Shadow sharpness When the sun is intense, your shadow or the shade cast by other objects is deep and dark with sharply defined edges. When the sun is less intense or there is cloud cover, shadows are less deeply colored and their edges are blurry.
• Cloud cover The sun may not look as bright, but up to 60 percent of UV rays can penetrate through overcast skies. Smog, on the other hand, partially filters solar radiation.
• Sky color Azure, cloudless skies may invite you to sunbathe, but the deeper the blue, the more intense the radiation you’ll get.
• Breeziness When the wind is calm, so is the water. A still surface reflects a substantial amount of ultraviolet radiation, depending on the angle of the sun.
• Geography Thin, high-altitude air is less effective at screening out radiation than the denser air at sea level. For every 1,000 feet of altitude, the intensity of UV light increases about four percent.
• Solar flares You can’t see these per se, but radio and TV signal interference, frequent aurora borealis displays and delays in space shuttle flights all signs of increased solar activity are often mentioned in the news. The UV intensity can increase as much as 15 percent during times of solar-surface unrest.