Nutrition science is where surgery was in about 1650, you know, really interesting and promising, but would you want to have them operate on you yet?… - Michael Pollan

Aldous Huxley did his best to argue us out of the view that a chemically conditioned spiritual experience is false—and he did so long before we knew anything about cannabinoid or opioid receptor networks….He points out that mystics have always worked systematically to modify their brain chemistry, whether through fasting, self-flagellation, sleeplessness, hypnotic movement, or chanting.†
†Huxley suggests that the reason there aren’t nearly as many mystics and visionaries walking around today, as compared to the Middle Ages, is the improvement in nutrition. Vitamin deficiencies wreak havoc on brain function and probably explain a large portion of visionary experiences in the past.

The brain can be made to drug itself, as seems to happen with certain placebos. We don’t merely imagine that the placebo antidepressant is working to life our sadness or worry—the brain is actually producing extra serotonin in response to the mental prompt of swallowing a pill containing nothing but sugar and belief. What all this suggests is that the workings of consciousness are both more and less materialistic than we usually think: chemical reactions can induce thoughts, but thoughts can also induce chemical reactions.

The industrialization — and brutalization — of animals in America is a relatively new, evitable, and local phenomenon: No other country raises and slaughters its food animals quite as intensively or as brutally as we do. No other people in history has lived at quite so great a remove from the animals they eat. Were the walls of our meat industry to become transparent, literally or even figuratively, we would not long continue to raise, kill, and eat animals the way we do.