Not knowing your right from your left in nutrition can get you into trouble.
In biological systems, there is an issue called “handedness,” or “chirality.” It means that there are right-handed (“Dextrarotatory”) and left-handed (“Levorotatory”) versions of compounds, or “D” and “L” versions, or isomers, much as we have right and left hands, mirror images of each other. But a right-handed glove does not fit on your left hand and vice versa. Likewise, enzymes only recognize one or the other isomer, not both. Mammals are largely L-isomer creatures, due to specificity of enzymes for L-versions of compounds.
Most foods — and I mean real food, foods that are instinctively recognized as food by humans, such as shellfish, organ meats, berries, nuts, and roots–have proteins made of L-amino acid isomers, not D.
Things that don’t belong in the human diet, such as grasses from the family Poaceae, have plenty of D-isomer amino acids. Because enzymes are subject to the rules of chirality, human digestive enzymes, such as trypsin and chymotrypsin, that digest proteins receive a “stop” signal when they encounter an indigestible D-isomer in a protein, leaving that protein or peptide fragment undigested.
Add D-amino acids to the other generally indigestible components of wheat and grains. Beyond D-isomer amino acids, other indigestible components of the seeds of grasses include:
- Gliadin–While some gliadin is degraded to small peptides that act as opiates on the human brain, a substantial proportion of gliadin remains undigested. The intact, undigested form is the form that initiates the zonulin mechanism that increases intestinal permeability, the first step in generating the diseases of autoimmunity.
- Wheat germ agglutinin (WGA)–The complex, 4-part protein present in wheat, rye, barley, and rice is completely indigestible. WGA that enters the mouth comes out the back end–except for the small quantity that penetrates intestinal barriers, causing direct intestinal toxicity and entering the bloodstream to activate antibodies, mimic insulin, and block leptin (the hormone of satiety).
- Trypsin inhibitors–Trypsin inhibitors block–no surprise–trypsin, a protein required for protein digestion. This further reduces the digestibility of grain proteins, a fact that organizations, such as the World Health Organization, grapples with when starving nations are fed grains but then struggle with malnutrition despite the calories.
There is a digestible component of wheat and the seeds of other grasses: the amylopectin A carbohydrate, highly susceptible to digestion by the amylase enzyme of saliva and stomach. This explains why two slices of whole wheat bread raise blood sugar higher than six teaspoons of table sugar. If you were starving, no real food in sight, and found yourself in a field of wheat, you could indeed harvest the seed, pulverize it, and eat it as porridge or ground into flour. It would serve as a source of carbohydrates and a minor source of proteins and oils. But you would soon suffer poor health and malnutrition, then die, as Homo sapiens cannot survive on the mix of components in the seeds of grasses.
If it often seems that there are SO many problems with wheat and grains, well, that’s because they never belonged in the human diet in the first place. Yes, we have committed a 10,000-year long mistake that began in desperation when we ran low on real foods, turning to the wild fields of grasses and harvesting their seeds. The food of desperation is now the food celebrated by all official agencies.