Epidemiologist Scott Davis warns, “Melatonin supplements are not regulated” the way drugs are. . . . “There may be all kinds of impurities and contaminants.” Are you really going to tell me that you aren’t going to take melatonin—if you’re convinced that it might lower your chance of getting cancer by as much as 50 percent—because you are afraid of impurities?

James Street
Oakland, Calif.

Might this article have missed something? If the daily light-dark cycle affects melatonin, is there a seasonal change in cancer rates in the Northern (and Southern) Hemispheres? If so or not, that might give a clue to any latency period.

Alan MacGregor
Salmon Arm, B.C.