Research published in the Journal of Steroid Biochemistry and Molecular Biology demonstrates that there is a strong inverse relationship between exposure to sunlight and the risk of pancreatic cancer, one of the very deadliest cancers.[1] The researchers assessed the association between sun exposure and the incidence of pancreatic cancer worldwide. Those living in countries closer to the equator would be expected to have greater sunlight exposure that those who lived in darker northern or southern countries. The investigators, however, took it one step further; they adjusted the data for cloudiness, which allowed them to determine if the sunnier countries with greater cloudiness had populations with greater pancreatic cancer risk than those sunnier countries with few clouds, and also the influence of clouds in countries farther from the equator.
The results were stunning—at least for the uninitiated. UVB irradiance (sunlight exposure) was inversely associated with pancreatic cancer, meaning that the greater the exposure to sunlight, the lesser the risk of pancreatic cancer. Dr. Cedric Garland, the lead researcher, made the following statement: “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.”[2]
Chalk up another victory for sunlight against disease. Many scientists and much of the lay public would probably determine that the operative factor in lowering pancreatic-cancer risk was increased vitamin D blood levels. However, that may not be true. Another investigation assessed blood levels of vitamin D compared to the risk of pancreatic cancer in male smokers. Subjects were measured for vitamin D and vitamin D-binding protein (DPB)[3] and then placed in five groups (five quintiles), according to their D levels; in other words, those with the highest vitamin D levels (measured as 25(OH)D) would be placed in quintile five; the lowest in quintile one. Amazingly, those in the both the highest quintile and the lowest quintile had considerably higher risk of cancer: Compared to the average (or referent) vitamin D levels, those in the highest quintile had 3.5 times the risk of pancreatic cancer, and those in the lowest quintile had 2.5 times the risk. The authors stated, “Our results do not support the hypothesis that serum DBP or 25(OH)D plays a protective role in pancreatic cancer.”
This is not mentioned to denigrate vitamin D, which is one of the very most important photoproducts produced by the skin after being exposed to sunlight. The lesson to be learned here, however, is that Sunlight produces many other substances that may fight diseases. VITAMIN D MAY NOT WORK FOR PANCREATIC CANCER, BUT SUNLIGHT DOES WORK. We need to sunbathe or find other sources of UVB light to protect ourselves when the sun doesn’t shine. Throwing a vitamin D pill at a disease may in many cases may be helpful, but it is no substitute for sunshine.
[1] Garland CF, Cuomo RE, Gorham ED, Zeng K, Mohr SB. Cloud cover-adjusted ultraviolet B irradiance and pancreatic cancer incidence in 172 countries. J Steroid Biochem Mol Biol. 2015 Apr 9.
[2] University of California, San Diego Health Sciences. “Pancreatic cancer risk linked to weak sunlight: Harm may come from low vitamin D.” Science Daily, 30 April 2015.
[3] Piper MR, Freedman DM, Robien K, Kopp W, Rager H, Horst RL, Stolzenberg-Solomon RZ. Vitamin D-binding protein and pancreatic cancer: a nested case-control study. Am J Clin Nutr. 2015 Apr 22.