Apparently the gut, uniquely, operates without being controlled by the brain and contain 95% of our seratonin, according to an article in today's Sunday Telegraph newspaper in the UK. The gut contains 100 million neurons and 40 neurotransmitters.

This is so consistent with "doing the food" and the old saying "you are what you eat".

http://www.telegraph.co.uk/health/women_shealth/9197756/What-your-guts-telling-you-why-your-digestion-holds-the-key-to-your-health.html