The importance of vitamin D, which is metabolised by the body from sunlight's ultraviolet B radiation, has been underlined by researchers from the University of California at San Diego.
They point out that sunlight is by far and away the most important source of the vitamin. In the food we eat, fatty fish, such as salmon and tuna, are rich sources, while beef liver, cheese and egg yolks provide small amounts.
The significance of strong sunlight is highlighted by the fact that pancreatic cancer is relatively rare around the Equator, where it affects just one-sixth of the population compared to that in the north, where the sun is either weak or rarely seen because of cloud cover.
The researchers examined levels of the cancer in 172 countries.
(Source: Journal of Steroid Biochemistry and Molecular Biology, 2015; doi: 10.1016/j.jsbmb.2015.04.004)