Trees and plants have roots - and they are essential to health.
Human beings have digestive systems ("the guts")
Ancient doctors knew that the health of the gut was essential for health and happiness.
After a multi-decade antibiotics spree, modern science is finally figuring it out too.
What you eat (uncontaminated, unprocessed foods), when you eat (no late night snacking) and how you eat (chew well, take your time) can make a huge difference when you establish these these practices as habits.