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Weak Sunlight Exposure May Be a Risk Factor in Pancreatic Cancer

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Key Points

  • Insufficient levels of vitamin D may contribute to an increased risk of pancreatic cancer.
  • Previous studies identified a link between high latitude and increased risk of pancreatic cancer.
  • The current study found that an estimate of solar ultraviolet B adjusted for heavy cloud cover produces an even stronger prediction of pancreatic cancer risk.

Researchers at University of California San Diego School of Medicine recently found that pancreatic cancer rates are highest in countries with the least amount of sunlight. These findings were published by Garland et al in The Journal of Steroid Biochemistry and Molecular Biology.

“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 Cedric F. Garland, DrPH, Adjunct Professor in the Department of Family Medicine and Public Health and Member of UC San Diego Moores Cancer Center.

“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. The importance of sunlight deficiency strongly suggests—but does not prove—that vitamin D deficiency may contribute to risk of pancreatic cancer.”

Study Details

The UC San Diego team, led by Dr. Garland and Edward D. Gorham, PhD, Associate Professor in the Department of Family Medicine and Public Health, had previously shown that sufficient levels of a metabolite of vitamin D, known as 25-hydroxyvitamin D, was associated with substantially lower risk of breast and colorectal cancer. Their newer research is the first to implicate vitamin D deficiency with pancreatic cancer.

Researchers studied data from 107 countries, taking into account international differences and possible confounders, such as alcohol consumption, obesity, and smoking. “While these other factors also contribute to risk, the strong inverse association with cloud-cover adjusted sunlight persisted even after they were accounted for,” said Dr. Garland. 

UC San Diego researchers had previously identified an association of high latitude with a higher risk of pancreatic cancer. Dr. Garland said the new study advances that finding, by showing that an estimate of solar ultraviolet B that has been adjusted for heavy cloud cover produces an even stronger prediction of risk of pancreatic cancer.

Vitamin D is often added as a fortifying nutrient to milk, cereals, and juices, and can be found naturally in food like fatty fish, beef liver, cheese, and egg yolks. But experts say most people also require additional vitamin D—specifically, ultraviolet B radiation—produced by the body by exposing skin directly to sunlight. Cloudy skies, shade, and dark-colored skin also reduce vitamin D production.

Pancreatic cancer is the 12th most common cancer in the world, according to World Cancer Research Fund International, with 338,000 new cases diagnosed annually. Incidence rates are highest in North America and Europe, and lowest in Africa and Asia.

This study was supported in part by the UC San Diego Department of Family Medicine and Public Health.

Raphael Cuomo, MPH, CPH, is the corresponding author for The Journal of Steroid Biochemistry and Molecular Biology article.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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