Here is a mind-bending question for you: When you swallow a piece of food, is it really inside your body?
Alison’s comment had gotten me thinking. “If you think about it,” she said, “your skin and your colon are connected.” The skin of the face is connected to the lips, which are connected to the inside of the mouth, which leads to the esophagus, the stomach, the intestines, the colon, the rectum, the anus…and finally, back to the outer skin of the body! (The leg bone’s connected to the/hip bone…)
Your digestive tract is a long tube passing through you. Through this tube, you interact with the food you’re digesting. Some molecules of that food pass all the way through you without ever crossing the walls of the tube–without ever entering your bloodstream. Those molecules go in your mouth and exit your butt and, voila!, they are back out in the world again.
Looking at it this way, your digestive tract is like an inner skin. Your outer skin is covered in bacteria, and interacts constantly with the outer world. Skin absorbs nutrients and toxins, and excretes toxins as well. Likewise, trillions of bacteria inhabit your inner skin, your colon and intestines, and these, too, are porous layers that take in and remove substances.
The digestive tract, then, is the site of a mystifying interface: the distinction between what is “me” and what is “not me.” It is the boundary that makes this decision, constantly, for your body. And it is a fuzzy boundary. Because who’s to say where, exactly, the boundary ends? Are my gut bacteria a part of me? Their populations fluctuate with my food and toxins and hormones, like independent colonies living on the surface of a planet, and yet they influence my health profoundly. At what point does a molecule of food become a part of me: when I swallow it, when it begins interacting with my stomach acids and gut bacteria, or only when it physically passes through the lining of my digestive tract and into my bloodstream?
For me, this thought elevates digestion to a profound and almost magical act. Likewise with breathing, another wondrous interaction between my body and the world, as I take in air from outside myself and bring it into my body, where some of it enters my bloodstream and becomes a part of me.
My mind opens when I think this way. I see the way my body is a part of the world, not apart from it. I interact constantly with the things around me, the things I touch and take in, the molecules of dust and leaves and tomatoes and beef and Cheerios and cat dander and plastic. I see the awesome ability of my unconscious, automatic systems to distinguish (I hope) what should become a part of me and what should not, the hard work my skin and lungs and digestive organs do to protect me and build me and keep me alive and healthy. I am made of the world, and I am part of the world.