Soil and Human Intestines

by Bill Duesing

First broadcast on WSHU/WSUF-FM, May 28, 1999

Healthy, fertile soil, which is literally teaming with living things, is the foundation of organic growing. A doctor friend once told me that he could sterilize surgical instruments with good garden soil because it contains so many beneficial and benign organisms (up to six billion in a teaspoonful) that pathogenic germs can't survive. This concept is a little easier to grasp if you consider the opposite end of the spectrum. Many of the most virulent organisms exist in places like the drains in hospitals and meat-packing plants, where germicides have been used to keep anything living (other than patients, that is) under control.

Soil organisms (especially the decomposers, bacteria and fungi) break down organic matter into simpler molecules which provide plant nutrients and build humus. The tough fibers in straw and wood are particularly valuable for creating the most stable and long-lasting humus, that ever-changing, not-fully-understood, almost magical substance which has so many beneficial effects in the garden.

In talking about soil, I've often compared the need for fiber there with the importance of fiber in the human diet. Now I understand how appropriate this analogy is.

In a recent talk at Yale University, Sidney Baker, a physician from Weston, clearly connected the digestive processes in the soil, with similar processes inside the human body. Apparently, every adult has a surface the size of a tennis court lining his or her intestines. This surface is inhabited by bacteria and fungi similar to those found in healthy soil. According to Dr. Baker, the one hundred trillion organisms in each human's gut constitute the second largest organ in the body. This "organ" which is integral to our nutrition but is not genetically human, is metabolically active and changeable. It contains over 300 species, mostly bacteria with a few kinds of fungi.

These intestinal organisms perform numerous chemical functions. From the passing stream of food, they synthesize vitamins, turn fiber into the nutrients needed by cells lining the intestines, and create metabolically-active substances which have effects throughout the body. A healthy, balanced intestinal ecosystem is as important to our well-being as fertile soil is to a healthy garden.

Of course, the ecosystem in our intestines, like that in the soil or the rain forest, can be upset by environmental insults. Antibiotics are one common cause of excess growth of fungi and undesirable bacteria. When these organisms "practice chemistry," the compounds they make can be damaging to our health, causing symptoms in other parts of the body that are commonly attributed to a disease. Conditions as diverse as autism and "fish odor syndrome" seem to be connected with faulty digestion which produces damaging chemicals.

Our digestive system evolved over hundreds of eons before the advent of agriculture and many of the foods that we eat today. Dr. Baker pointed out that our diets have changed faster than our digestive processes. The average modern diet provides just one fifth the amount of fiber eaten by most of our ancestors. Foods such as milk and cereal grains are, relatively speaking, very recent additions to our diets.

Given our long evolution on this planet, it is not surprising that our insides are connected with the outside- that the processes in the soil are similar to those in our guts. They are both part of nature's cycling. The wastes which result from our intestinal processes have the same nearly-neutral pH as good compost. The roots and stems of rye are one of the best ingredients for building fertile soil. The fiber from rye bread seems to be especially beneficial to our intestines.

Over the last century, humans have made major changes to soil microbiology with agricultural chemicals and to intestinal ecology with new foods and chemicals. Although there is much more to learn about soil ecology and human digestion, evidence suggests we should show greater respect for microbiological processes.

The organic garden, which uses a variety of plant residues to build healthy soil and produces nutrient and fiber-rich fruits and vegetables for us to eat, is a good way to begin.

This is Bill Duesing, Living on the Earth


This page and its contents are copyright © 1999 by WSHU-FM, Fairfield, CT, and by Bill Duesing.