Sunlight Helps Put Lung Cancer in the Shade

MONDAY, Dec. 17 (HealthDay News) -- Something as common and availableas sunlight may help prevent some lung cancers, researchers say.
A new study finds that lower levels of the sun's ultraviolet B (UVB)rays are associated with a higher incidence of lung cancer across 111countries.
Still, that doesn't mean that spending more time in the sun will everoffset the risks that come with smoking, according to the study, which ispublished in the January issue of the Journal of Epidemiology andCommunity Health.
It's also not an excuse to trade skin cancer for lung cancer.
"The problem is that people might over-interpret this and stay in thesun for hours," said Cedric Garland, study senior author, professor offamily and preventive medicine at the University of California, San Diego(UCSD), and participating member at the Moores UCSD Cancer Center in LaJolla.
Too little sun isn't great either, however, since sunlight helps theskin manufacture healthy vitamin D. "It would be false prudence to stayout of the sun to prevent skin cancer and not get enough vitamin D,"Garland said.
Other experts, however, feel the focus should stay on cigarette smokingas the number one cause of lung cancer.
"When you have such a strong factor as tobacco, it really weighs outall these other small influences," said Dr. Jay Brooks, chairman ofhematology/oncology at the Ochsner Health System in Baton Rouge, La. "It'sa very interesting observation, but the main message is tobacco is such astrong influence in the development of lung cancer that we shouldconcentrate on that."
More than one million people die of lung cancer worldwide each year.Cigarette smoking causes about 85 percent of lung cancers. The remainingcases are caused by exposure to secondhand smoke and a variety of other(some unknown) factors.
Sunshine is a significant source of vitamin D, as the sun's UV raystrigger synthesis of vitamin D in the skin.
Previous research, much of it by the same group, has found a strongassociation between breast cancer, colon cancer and other internal-organcancers and living in latitudes with less sunlight. For example, one paperobserved double the death rate from colon cancer above the U.S.Mason-Dixon line as below, leading the researchers to focus on lack ofsunlight as the culprit.
It wasn't a new idea. "There were people in epidemiology dating back toHippocrates who thought it was a good idea to live on the south side of ahill," Garland said.
Another study linked lower levels of a vitamin D metabolite in theblood with a higher level of colon cancer.
For this study, Garland and his colleagues looked at the associationbetween latitude and exposure to UVB light and rates of lung cancer in 111countries. Data came from an extensive United Nations database.
Although smoking showed the strongest association with lung cancer,exposure to UVB light also had an impact.
UVB light is greatest closer to the equator. This study showed thatlung cancer rates were highest in regions farthest away from the equatorand lowest in those regions nearest to it.
Higher cloud cover and aerosol use (both of which absorb UVB rays) werelinked with higher rates of lung cancer.
For men, smoking was associated with higher rates of lung cancer, whilegreater exposure to sunlight was associated with lower rates.
For women, cigarette smoking, along with total cloud cover and aerosollevels, were associated with higher rates of lung cancer, while sunlightwas again associated with lower rates.
Previous research has indicated that vitamin D may be able to stop thegrowth of malignant tumors.
"Everyone should be taking vitamin D, and, at all latitudes, there'splenty of potential to make vitamin D," Garland said. "Even in Helsinki,people can take advantage of the sun in summer months."
And vitamin D produced in the summer will carry over into the winter.Even so, unless you know what your vitamin D levels are, it might be wiseto take a supplement, Garland advised.
More information
For more on vitamin D, head to the U.S. National Institutes of Health.