Study: More Vitamin D May Lower Lung Cancer Rates

Another form of cancer seems to be positively affected by the sun, according to a recent study published in the January issue of the Journal of Epidemiology and Community Health. The study found that lower levels of ultraviolet B (UVB) rays are associated with a higher incidence of lung cancer across 111 countries.

This study, along with many others, suggests that we need to reevaluate the amount of time we spend in the sun. While too much sun is not a good thing, too little sun isn't great either because sunlight helps the skin manufacture healthy vitamin D.

“It would be false prudence to stay out of the sun to prevent skin cancer and not get enough vitamin D,” says the study’s senior author Cedric Garland, a professor of family and preventive medicine at the University of California, San Diego (UCSD), and participating member at the Moores UCSD Cancer Center in La Jolla, Calif.

Previous research, much of it by the same group, has found a strong association between breast cancer, colon cancer and other internal-organ cancers and living in latitudes with less sunlight. For example, one paper observed that the death rate from colon cancer in areas above the U.S. Mason-Dixon line was double that of the rates below the line, leading the researchers to focus on a lack of sunlight as the culprit. Another study linked lower levels of a vitamin D metabolite in the blood with a higher level of colon cancer.

For the current study, Garland and his colleagues looked at the association between latitude, exposure to UVB light and rates of lung cancer in 111 countries, using figures came from an extensive United Nations database.

Although smoking showed the strongest association with lung cancer, exposure to UVB light—which is greatest closer to equator—also had an impact. The study showed that lung cancer rates were highest in regions farthest away from the equator and lowest in those regions nearest to it. Higher cloud cover and aerosol use (both of which absorb UVB rays) also were linked with higher rates of lung cancer.

For men, smoking was associated with higher rates of lung cancer, while greater exposure to sunlight was associated with lower rates. For women, cigarette smoking, total cloud cover and aerosol levels were associated with higher rates of lung cancer, while sunlight was again associated with lower rates.

“Everyone should be taking vitamin D—and, at all latitudes, there's plenty of potential to make vitamin D,” Garland says. “Even in Helsinki, people can take advantage of the sun in summer months.”