Prebiotic fibers are an essential component of the Wheat Belly program, as they are necessary for cultivating microbial life in the gastrointestinal tract. I’m glad that we now have insights into the importance of prebiotic fibers, having wasted decades being concerned about cellulose fibers that are indigestible by both humans and microbes and achieve little more than bulking up stool, but do not nourish bacteria. Millions of people still choose foods like bran cereals for their cellulose fiber content in the hopes of better bowel and overall health with no awareness that they are missing out on the impressive power of prebiotic fibers, i.e., the form of fiber that provides genuine health benefits, not just bulkier bowel movements. And, of course, if they amp up cellulose fiber intake with fiber-rich bran cereals, they are also exposing themselves to the autoimmune disease-causing gliadin protein, gliadin-derived opioids that increase appetite, phytates that bind minerals in the gut and make them unavailable for absorption, and blood sugar-raising and type 2 diabetes-causing amylopectin A.
Obtaining plentiful quantities of prebiotic fibers is therefore an enormous advantage for health. Besides improving bowel regularity, prebiotic fibers are known to be protective of the intestinal lining; yield improvements in insulin resistance, blood sugar, and blood pressure; help reverse fatty liver; improved immune function; among a number of other benefits. Many of these benefits derive from microbial fermentation of prebiotic fibers to the fatty acid, butyrate, that acts both on the intestinal lining as well as being absorbed to transact benefits outside the intestinal tract. NOT getting sufficient prebiotic fibers (we aim for a minimum of 20 grams per day) therefore leads to health issues.
Among the effects of inadequate prebiotic fiber intake are:
- Excessive proliferation of Akkermansia muciniphila—Increasing the population of this species is beneficial, leading to effects that include reduced blood sugar and insulin resistance when Akkermansia represents around 8-9% of total bacterial counts in the colon. But overproliferation (e.g., 12-13% of total bacterial population) of this species, as happens when you fail to take in prebiotic fibers that cause this bacteria to turn to consuming the human mucous lining—muciniphila = mucous-loving—causing the protective mucous barrier to thin, thereby encouraging intestinal inflammation and increased intestinal permeability and metabolic endotoxemia. In other words, in the absence of prebiotic fibers, fiber-consuming species die or are reduced in number, allowing mucous-consuming Akkermansia to dominate. In experimental models, this process yields fatal colitis.
- Rise in intestinal pH—In the absence of prebiotic fibers, there is a sharp reduction in short-chain fatty acid production. As a result, the pH of the colon and distal small intestine rise, i.e., become less acidic and more alkaline. A prebiotic fiber-rich diet tends to yield a colonic pH of 6.3 or less. Without prebiotic fibers, pH rises to 6.5 or higher, creating an environment that encourages growth of Enterobacteriaceae, the species of small intestinal bacterial overgrowth, SIBO. Development of SIBO, of course, invites a constellation of downstream health consequences of its own including seemingly unconnected conditions such as coronary disease, rosacea, fibromyalgia, and dementia.
- Metabolic distortions—Lack of prebiotic fibers leads to reduction in bacterial products such as butyrate that microbes produce from prebiotic fibers. This results in lower HDL, higher triglycerides, greater numbers of small LDL particles, higher blood sugar, greater insulin resistance, higher blood pressure, as well as inflammation and impaired healing of the intestinal lining that depends on butyrate.
Here is a Wheat Belly Blog post listing many common sources of prebiotic fibers that you should add to your routine. The photo above shows some Chocolate-Coated Green Banana Bites, a tasty way to add prebiotic fibers from an unripe banana. But remember: If you prove intolerant to prebiotic fibers and experience excessive bloating, abdominal discomfort, diarrhea, or emotional effects such as anxiety or depression, especially within the first 60 minutes of consumption, this is virtually diagnostic of small intestinal bacterial overgrowth, SIBO, that will need to be addressed.