While researching the book, Pollan did what many of us would find intolerable: He gave up caffeine for three months reports USA Today.

Pollan interviewed Dr. Matthew Walker, a neuroscientist and the director of the Center for Human Sleep Science at Berkeley, as well as the author of “Why We Sleep: The New Science of Sleep and Dreams.” Walker argues that lack of quality sleep is a hidden public health crisis, and one of the primary culprits of the epidemic is caffeine. Even having just a morning cup of coffee can wreck sleep: Caffeine ingested early in the day can still be in your system when your head hits the pillow. 

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