Edward Calabrese, a toxicology professor at the University of Massachusetts, has pointed to the existence of U-shaped dose-response functions in a great many cases. Chemicals harmful at high doses are helpful at low dose, a phenomenon called hormesis. He reviews the evidence here and here. I didn’t know that a low dose of dioxin reduces tumors. Nor did I know that a low dose of saccharine likewise reduces tumors.
The theory behind hormesis is that a damage-repair system is stimulated by the toxin. This isn’t far from my idea that the average American’s immune system is woefully understimulated, with many bad consequences (allergies, cancer, etc.), due to too-sterile food. If the rats or whatever used in the hormesis studies — probably fed sterile lab chow — were given immune system stimulation (e.g., from fermented food), the hormesis effect might disappear.
Thanks to JR Minkel.