Weighing the evidence linking UVB irradiance, vitamin D, and cancer risk

摘要

To the Editor. A recent article concluded that evidence of a beneficial role of vitamin D in reducing the risk of cancer incidence and mortality is not impressive, in part because of a lack of good randomized controlled trials (RCTs). Randomized controlled trials are appropriate for studying pharmaceutical drugs but not necessarily for vitamin D. Most vitamin D is produced from solar UVB irradiance and confounds oral intake in RCTs of vitamin D. Nested case-control studies are less reliable than case-control studies because the relation of a single serum 25-hydroxyvitamin D [25(OH)D] level measurement to subsequent serum 25(OH) D levels declines with the passage of time, and undetectable cancers can grow rapidly in the absence of adequate serum 25(OH)D levels.