The microbes that live in our digestive tract can either be our closest friends, or our most bitter enemies. The Standard American Diet (SAD) full of antibiotic laden meat and dairy products, as well as preservative laden processed foods, tends to kill off the friendlier organisms in our gut and encourages the flourishing of decay organisms. These decay organisms come along with the meat and dairy, upon which they flourish. The consequent disruption of our microbiome, or dysbiosis, has been linked to diseases as diverse as heart disease, depression and cancer.
In my first article in this series—They’ve Got Us Covered—I talked about the role of the microbiome as a major component of our immune system. The microbes not only cooperate with the lymphatic system in training the developing immune system to discriminate between friend and foe, but the microbiome actually produces special metabolites that feed the immune cells to keep them healthy, and biotoxins to fight off disease organisms. The microbiome is our first line of defense against encroaching disease organisms, and makes up roughly seventy percent of our immune system.
Not surprisingly, the strongest correlations have been found between dysbiosis and conditions such as Crohn’s disease, irritable bowel syndrome and diverticulosis which effect the lining of the gut. These diseases have been shown to improve significantly through interventions involving diet change. High fiber content being the key to a health intestinal tract.
Doctors routinely prescribe antibiotics to patients with these painful bowel diseases. While antibiotics may be indicated where infection is present, the routine use of antibiotics can cause these diseases to worsen. Antibiotics will devastate the microbiome, which is the only thing that can heal the damaged tissues of the colon. Instead of killing off our protective microbes, we need to be encouraging their proliferation by increasing the prebiotic fiber content of our diet.
The Fiber of Our Being
For many years scientists believed that the only purpose for fiber was to push waste through the digestive system, so that food would not rot in our gut. However, recent evidence has shown that fiber serves many purposes. It can lower our cholesterol by binding it so that it is excreted, help to slow the progress of digestion so that nutrients can be fully exploited, and lower the pH of bowel contents which makes for a more hospitable environment for our colon lining. High fiber intake has been linked to lower rates of heart disease, diabetes, several cancers (including colon, breast and prostate cancers) and, of course the very bowel diseases that we are addressing.
Because dietary fiber has been shown to help in cases of Crohn’s disease, Irritable Bowel Syndrome, diverticulosis and other intestinal issues, doctors often suggest that a patient supplement their diet with a commercial fiber supplement like Benefiber, Citrucel or Metamucil. Though these products may help to relieve symptoms, it would take a great quantity of the supplements to equal the amount of fiber consumed in a healthy diet. The supplements are also lacking in the multitude of nutrients that one would obtain from eating whole fiber rich foods like whole grains, legumes, fruits and vegetables. It is best to get our fiber from whole foods.
There are two broad categories of dietary fiber presently identified by nutrition science—soluble and insoluble fiber. Soluble fiber dissolves readily in water, becoming gelatinous, while insoluble fiber can pass through the digestive system largely intact. The basic definition of dietary fiber is that it cannot be digested with human enzymes. However, our microbiome is capable of digesting many types of fiber of both the soluble and the insoluble varieties, through an elaborate process that involves fermentation.
Fiber is the food of a healthy microbiome. When we eat adequate quantities of fiber, our microbiome thrives. It in turn converts the fiber into short chain fatty acids like butyrate, acetate and propionate. Butyrate is the preferred food of the cells that line our colon. If we don’t eat enough fiber, our colon sickens and starves to death. This is the primary reason for the many diseases that afflict our intestinal tract. They are, in essence, fiber deficiency diseases. The only way to heal these tissues is to eat a broad range of whole grains, legumes, vegetables, fruits, nuts and seeds to consume the full breadth of fiber varieties to feed our microbiome. A healthy microbiome in turn feeds our colon cells, as well as all the other tissues of the body.
Early researchers discovered one variety of soluble fiber, which was then named resistant starch. The researchers identified it as the specific type of fiber that the microbiome converted to short chain fatty acids. Their enthusiasm for isolating one fiber type had a great deal to do with pharmacological application. By isolating a component of food that could help heal the intestinal lining, commercial interests might be able to patent the substance for sale. Indeed, that is precisely what happened. Resistant starches, also commonly called Prebiotics, have become a popular healthy food craze.
As research has progressed, however, scientists discovered that resistant starch is just one variety of fiber that our microbiome uses. They have even proposed throwing out the two broad categories of soluble and insoluble fiber as being relatively useless. More important than whether the fiber is water soluble is the property of being fermentable by our gut microbes. Fermentable fiber encompasses a great variety of of both soluble and insoluble fiber types. Resistant starch is just one of those types, among many. Commercially prepared resistant starches have the same constraints as earlier commercial soluble fiber products. Isolating one variety of fiber will encourage the growth of isolated types of microbes. It is as if we are feeding a person nothing but corn. Though it may keep them alive for a time, they will not be getting everything they need to remain healthy. Our microbiome requires a range of nutrients and fiber types from a broad variety of whole foods.
Feeding Our Friends
The first thing we need to remember is that animal products—meat, dairy and eggs—contain no fiber. The Standard American Diet (SAD) is high in animal products and consequently much too low in fiber. Animal product consumption has risen over the last several decades to the detriment of our health.
Many people excuse their consumption of meat and dairy under the rubric of a need for protein. [See former essays The Protein Question–Part One and The Protein Question–Part Two] Yet, anyone who consumes adequate calories of whole plant foods will get more than enough protein in their diet. In the process they will not only get all of protein they need, but also all of the fiber that they need to feed a healthy, diverse microbiome.
Plants are not only the consummate meal for our microbiome, but plant-based protein is also less sulfurous. The sulfur content in meat, dairy and eggs is turned into hydrogen sulfide in our guts, which not only gives our gas that disgusting rotten egg smell, but also plays a significant role in the development of inflammatory bowel disease. This may be one reason why study after study show links between animal protein and inflammatory bowel disease. The more meat study participants ate, the more sulfide was generated by their gut microbes. This translates into more risk for inflammatory bowel disease. The only way to avoid the risk is to eat a plant based diet.
Feeding our gut microbiome animal protein encourages the growth of bacteria that metabolize sulfurous amino acids into sulfuric acid that damages our colon cells. On the other hand, feeding our microbiome plants encourages the growth of bacteria that metabolize fiber into helpful short chain fatty acids like butyrate that keep our colon healthy. The science is clear.
Why then do so many people, including some doctors, recommend avoiding carbohydrates? The first reason that there is so much backlash against carbohydrates has to do with the prevalence of refined carbohydrates in the Standard American Diet. Refined foods like white sugar, high fructose corn syrup, white flour and white rice are extracted elements of whole food. They do not contain the full nutritional value of the whole food from which they were extracted. Chief among the elements that are left behind in the refining process is the fiber from these foods. Without the fiber, they cannot feed our microbiome. In addition, the processed foods that include these elements generally contain preservatives and other artificial ingredients that can be harmful to our microbiome as well as our bodies.
Another reason that people recommend against the consumption of carbohydrates is that a sudden drastic increase in fiber intake can cause bloating and diarrhea even in normal people. It will take from a few days to up to two weeks for the system to regulate to the new level of intake. This is not because fiber is bad for the colon, on the contrary. Any drastic change in diet will cause the same symptoms as the microbiome readjusts. If the symptoms are unbearable it may be wise to make the adjustment more slowly. However, this may only prolong the period of discomfort. Patience is called for.
Second Only to Lung Cancer
Perhaps slightly more surprising than the connection between dysbiosis and bowel disease is the correlation found between dysbiosis and colorectal cancer. Most people think of cancer as being largely genetic in origin, and therefore a weakness we inherit from our parents. They would be startled to learn that no more than five to ten percent of cancers actually arise from such inherited weaknesses. Even those who inherit the propensity to succumb to the disease do not all fall victim to cancer.
T. Colin Campbell PhD devoted the majority of his life’s work, over thirty years of research, to studying the connection between animal protein and cancer. He was one of the chief scientists involved in the China-Cornell-Oxford Project, which has been acclaimed as the most thorough study of the connection between disease and nutrition. His book The China Study, written with his son Thomas M. Campbell M.D. as a coauthor, was characterized by The New York Times as “the Grand Prix of epidemiology.” Campbell observed that, “The expression of the genes is controlled by nutrition: Even when genetically pre-disposed, nutrition trumps genes. Genes may load the gun, but lifestyle pulls the trigger.”
All told, environmental factors play the largest role in the development of cancer. This may be especially true of colorectal cancer. What we eat has a greater chance of interfacing with our bodies for a prolonged period of time than any external environmental factor may have. This intimate connection to our food allows carcinogenic substances to have a maximal impact. Food remains in the colon anywhere from several hours to several days, depending on the type of foods eaten. Since they lack fiber—which can have the effect of hastening the passage of food—meat can remain in the colon for a greater amount of time than plant foods, allowing it to essentially rot in our guts. It is no surprise that our guts rot along with it!
Carnivores have adapted to the dangers of their dietary preference by evolving a short, straight colon which allows rapid transit of their waste. Our colons resemble that of obligate herbivores, it is curved and several times longer than the obligate carnivore colon. The transit time for meat, even when mixed with fiber filled foods like beans, whole grains or fruits may be too long to avoid damage to our colon cells.
Many studies have been found connecting the consumption of meats, particularly those high in saturated fat, with colorectal cancer (this study for example, and this study). A recent study analyzing the increasing incidence of colon cancer in Shanghai China found that the rise in risk is linked to higher consumption of meat, including fish, and a lower consumption of fruits and vegetables. The connection between meat consumption and cancer risk can be traced
in great part to the effects of diet on the microbiome. With the elimination of meat from the diet, and a greater intake of whole plant foods, the microbiome can overcome dysbiosis to prevent the formation of cancer.
So closely linked are the microbiome with our physical health that recent scientific studies have shown that doctors can now predict whether a patient has cancer by looking at the composition of their microbiome—even head and neck cancers, far removed from the colon. Since our diet has the most direct impact on the composition of our microbiome, it is only logical to conclude that the causes of both the changes in the microbiome and the incidence of cancer are related to the diet. Combined with the findings from T. Colin Campbell’s studies, and many others related to his, it becomes imperative to change ones diet to a whole foods plant based diet in order to have the best possible chance of healing the body along with the microbiome.