[SeekAndFind]

Ann Coulter ( courting controversy again ) and a Nuclear Physicist claim: Some radiation is good for you

[FairWitness]

Ann is right; it's called "hormesis", a well documented observation in toxicology studies:
From Wikipedia: In toxicology, hormesis is a dose response phenomenon characterized by a low dose stimulation, high dose inhibition, resulting in either a J-shaped or an inverted U-shaped dose response. Such environmental factors that would seem to produce positive responses have also been termed “eustress.”

[rellimpank]

--there was a piece on this in National Review some years ago about a study of U. S. Navy submariners with the same finding--the study was supressed, IIRC---