People who live in regions with low sunlight may have a higher risk of pancreatic cancer, possibly because they don't get enough vitamin D from the sun, new research suggests.
"If you're living at a high latitude or in a place with a lot of heavy cloud cover, you can't make vitamin D most of the year, which results in a higher-than-normal risk of getting pancreatic cancer," said study co-author Dr. Cedric Garland.
He is an adjunct professor with the University of California, San Diego School of Medicine's Department of Family Medicine and Public Health.
"People who live in sunny countries near the equator have only one-sixth of the age-adjusted incidence rate of pancreatic cancer as those who live far from it," Garland said in a university news release. "The importance of sunlight deficiency strongly suggests -- but does not prove -- that vitamin D deficiency may contribute to risk of pancreatic cancer."
It's possible to get vitamin D from foods like fatty fish (especially salmon and tuna), cheese, egg yolks and fortified products like milk, cereal and juices. But people need more vitamin D than can be provided by food, according to the researchers.
That's where direct outdoor exposure to the sun comes in, since it boosts the body's production of vitamin D.
Garland and colleagues have previously linked higher vitamin D levels to lower levels of breast and colorectal cancer. Now, they're reporting a similar connection to pancreatic cancer.
The researchers reached their conclusions after reviewing information from more than 100 countries. They also adjusted their results so they wouldn't be thrown off by other risk factors, such as obesity, alcohol consumption and smoking.
Pancreatic cancer is an especially deadly form of cancer. It's the 12th most common type of cancer in the world, but the seventh most deadly, according to the researchers.
The study appears online April 30 in the Journal of Steroid Biochemistry and Molecular Biology.