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Page: << Prev | 1 | 2 Sunshine is a significant source of vitamin D, as the sun's UV rays trigger synthesis of vitamin D in the skin.
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 double the death rate from colon cancer above the U.S. Mason-Dixon line as below, leading the researchers to focus on lack of sunlight as the culprit.
It wasn't a new idea. "There were people in epidemiology dating back to Hippocrates who thought it was a good idea to live on the south side of a hill," Garland said.
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Another study linked lower levels of a vitamin D metabolite in the blood with a higher level of colon cancer.
For this study, Garland and his colleagues looked at the association between latitude and exposure to UVB light and rates of lung cancer in 111 countries. 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 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) 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, along with total cloud cover and aerosol levels, were associated with higher rates of lung cancer, while sunlight was again associated with lower rates.
Previous research has indicated that vitamin D may be able to stop the growth of malignant tumors.
"Everyone should be taking vitamin D, and, at all latitudes, there's plenty 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 wise to take a supplement, Garland advised.
More information
For more on vitamin D, head to the U.S. National Institutes of Health.
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