You can obtain considerable wisdom on human health and nutrition by considering what foods are ingestible (i.e., things you can swallow), indigestible (things you can ingest but cannot break down via digestion), and digestible (things that you can indeed break down into their components for nutrition). Understanding these distinctions can also clear up some previous mysteries surrounding food and health.
- The shell of a pistachio or peanut is ingestible, but woody cellulose shells are not digestible. There is therefore no advantage in consuming the shells of pistachios. This much is common sense.
- Fibers are ingestible but indigestible–you can swallow them but your stomach acid, enzymes, and bile cannot break fiber down into sugars. (All fibers are polymers, or chains, of sugar molecules.) Yet fibers that microbes are able to metabolize have been demonstrated to provide numerous, often extraordinary, health benefits. Microbes dwelling in your gastrointestinal (GI) tract possess the enzymes necessary to break down fibers and convert them to such things as butyrate that exerts many health effects to the human host. Despite their indigestibility by humans, the process provided by microbes yields magnificent health benefits such as reduced insulin resistance, reduced triglycerides/VLDL and thereby heart disease, enhanced immune response.
- As with fibers, polyphenols from vegetables and fruit are also ingestible but largely indigestible by humans. Once again, microbes can process and metabolize polyphenols (or provide other beneficial effects, such as cross-linking mucin proteins to strengthen the intestinal mucus barrier), yielding numerous health compounds for human hosts.
- Wheat germ agglutinin—the lectin protein of wheat is ingestible but completely indigestible to humans, also indigestible to microbes. It enters the human GI tract via a bagel, cookie, or sandwich, it exits the bowels into the toilet, fully intact, unchanged by human digestion and microbial metabolism. In its travels through the 30-feet of human GI tract, it exerts toxic effects, such as denuding the finger-like villi that line the intestines, causing intestinal inflammation, increased intestinal permeability and endotoxemia that results in inflammation in other organs. The inability of humans to digest wheat germ agglutinin and other partially digestible grain proteins (e.g., gliadin, glutenins) that exert potent toxic effects on us suggest that wheat and grains are inappropriate for human consumption. This makes sense, given their relatively recent addition to the human dietary menu, having been consumed less than one-half of one-percent (<1/2 of 1%) of human time on this planet.
In an ironic twist, while wheat contains indigestible or only partially-digestible components, it also contains rapidly digestible amylopectin A, the super carbohydrate responsible for extravagant rises in blood sugar and insulin resistance that develop with wheat consumption.
I view wheat as a cruel trick played on humans, a combination of highly-digestible sugars (amylopectin A) with indigestible toxic components (wheat germ agglutinin, gliadin, glutenins), a major source of the toxic heavy metal cadmium associated with various cancers and learning impairment in children, with gliadin protein-derived opioid peptides that act as appetite stimulants and can drive addictive eating behavior that make you want more.
I hope that you appreciate that the overly-simplistic thinking reflected in dietary guidelines and the advice of dietitians and doctors based on the observation that whole grains are less harmful than white flour products (see Wheat Belly Blog post, Smoke low-tar cigarettes?) means that many assessments like this are simply ignored. But it explains why a diet low in fat and rich in ‘healthy whole grains” cripples human health.