How strong is the evidence that solar ultraviolet B and vitamin D reduce the risk of cancer?
An examination using Hill’s criteria for causality William B. Grant Dermato-Endocrinology 1:1, 17-24; January/February 2009; ©2009 Landes Bioscience Summary and Conclusion
The solar UVB—vitamin D—cancer theory now satisfies most, if not all, of the criteria for causality in a biological system as initially postulated by Robert Koch and expanded by A. Bradford Hill.
Thus, from a scientific point of view, vitamin D reduces the risk of developing many types of cancer and increases survival once cancer reaches the detectable stage.
Unfortunately, health policy often lags scientific discoveries by years to decades. An example from the mid-19th century was the discovery by Ignaz Semmelweis that doctors carried germs from autopsies to women giving birth and infected them, resulting in puerperal sepsis.
A more recent example is the announcement by Barry Marshall and Robin Warren that Helicobacter pylori caused stomach ulcers. Although Marshall infected himself with H. pylori in 1981 and developed an ulcer,126 he concluded by 1995 that Koch’s postulates were not well satisfied.
However, in 2005, Marshall and Warren were awarded the Nobel Prize in Medicine. It is hoped that the acceptance of the beneficial role of vitamin D in reducing the risk of cancer and many other diseases will not have to wait much longer.
It is encouraging that the National Academy of Sciences’ Institute of Medicine (http:// www.iom.edu) is embarking on a 2-year study of vitamin D dietary requirements and is expected to issue a report in October 2010.