Thus, alterations of wheat that could potentially result in undesirable effects on humans are not due to gene insertion or deletion, but are due to manipulations that predate genetic modification. As a result, over the past sixty years, thousands of new wheat strains have made it to the commercial food supply and supermarket shelves without a single effort at safety testing. This is a development with such enormous implications for human health that I will repeat it: Modern wheat, despite all the genetic alterations to modify thousands of its genetically determined characteristics, made its way to the worldwide human food supply with nary a question surrounding its suitability for human consumption.
Because hybridization experiments did not require the documentation of animal or human testing, pinpointing where, when, and how the precise hybrids that might have amplified the ill effects of wheat is an impossible task.
The incremental genetic variations introduced with each effort at “improving” wheat strains can make a world of difference. Take human males and females. While men and women are, at their genetic core, largely the same, the differences clearly make for interesting conversation, not to mention romantic moments in dark corners. The crucial differences between human men and women, a set of differences that originate with just a single chromosome, the diminutive male Y chromosome and its few genes, set the stage for thousands of years of human life and death, Shakespearean drama, and the chasm separating Homer from Marge Simpson.
And so it goes with this human-engineered grass we still call “wheat.” Genetic differences generated via thousands of human-engineered manipulations make for substantial variation in composition, appearance, and qualities important not just to chefs and food processors, but also to human health.
WHETHER IT’S A loaf of organic high-fiber multi-grain bread or a Twinkie, what exactly are you eating? We all know that the Twinkie is just a processed indulgence, but conventional advice tells us that the former is a better health choice, a source of fiber and B vitamins, rich in “complex” carbohydrates, and your ticket to a life of slenderness and freedom from diabetes, heart disease, and colon cancer.
Ah, but there’s always another layer to the story. Let’s peer inside the contents of this grain and try to understand why—regardless of shape, color, fiber content, organic or not—it potentially does peculiar and harmful things to humans.
WHEAT: SUPERCARBOHYDRATE
The transformation of domesticated wild grass of Neolithic times into modern Cinnabon rolls, French crullers, or Dunkin’ Donuts requires some serious sleight of hand. These modern configurations were not possible with the dough of ancient wheat.
An attempt to make a modern jelly donut with einkorn wheat, for example, would yield a crumbly mess that would not hold its filling, and it would taste, feel, and look like, well, a crumbly mess. In addition to breeding wheat for increased yield, geneticists have also sought to generate strains with properties best suited to become, for instance, a chocolate sour cream cupcake or a seven-tiered wedding cake.
Modern Triticum aestivum wheat flour is, on average, 70 percent carbohydrate by weight, with protein and indigestible fiber each comprising 10 to 15 percent. The small remaining weight of Triticum wheat flour is fat, mostly phospholipids and polyunsaturated fatty acids.1 (Interestingly, ancient wheat has higher protein content. Emmer wheat, for instance, contains 28 percent or more protein.)2
Wheat starches are the complex carbohydrates that are the darlings of dietitians. “Complex” means that the carbohydrates in wheat are composed of polymers (repeating chains) of the simple sugar, glucose, unlike simple carbohydrates such as sucrose that are one- or two-unit sugar structures. (Sucrose is a two-sugar molecule, glucose + fructose.) Conventional wisdom, such as that from your dietitian or the USDA, says we should all reduce our consumption of simple carbohydrates in the form of candy and soft drinks, and increase consumption of complex carbohydrates.
Of the complex carbohydrate in wheat, 75 percent is the chain of branching glucose units, amylopectin, and 25 percent is the linear chain of glucose units, amylose. In the human gastrointestinal tract, both amylopectin and amylose are digested by the salivary and stomach enzyme amylase. Amylopectin is efficiently digested by amylase to glucose, while amylose is much less efficiently digested, some of it making its way to the colon undigested. Thus, the complex carbohydrate amylopectin is rapidly converted to glucose and absorbed into the bloodstream and, because it is most efficiently digested, is mainly responsible for wheat’s blood-sugar-increasing effect.
Other carbohydrate foods also contain amylopectin, but not the same kind of amylopectin as wheat. The branching structure of amylopectin varies depending on its source.3 Amylopectin from legumes, so-called amylopectin C, is the least digestible. Undigested amylopectin C makes its way to the colon, whereupon the symbiotic bacteria happily dwelling there feast on the undigested starches and generate gases such as nitrogen and hydrogen—hence the schoolkids’ chant, “Beans, beans, they’re good for your heart, the more you eat, the more you …”—making the sugars unavailable for you to digest but forcing you to excuse yourself from a business meeting.
Amylopectin B is the form found in bananas and potatoes and, while more digestible than bean amylopectin C, still resists digestion to some degree. The most digestible form of amylopectin, amylopectin A, is the form found in wheat and its grain brethren. Because it is the most digestible, it is the form that most enthusiastically increases blood sugar. This explains why, gram for gram, wheat increases blood sugar to a greater degree than kidney beans or potato chips. The amylopectin A of wheat products, complex or no, is a supercarbohydrate, a form of highly digestible carbohydrate that is more efficiently converted to blood sugar than nearly all other carbohydrate foods, simple or complex.
This means that not all complex carbohydrates are created equal, with amylopectin A–containing wheat increasing blood sugar more than other complex carbohydrates. The uniquely digestible amylopectin A of wheat also means that the complex carbohydrate of wheat products, on a gram-for-gram basis, are no better, and are often worse, than simple carbohydrates such as sucrose.
People are often shocked when I tell them that whole wheat bread increases blood sugar to a higher level than sucrose.4 Aside from some extra fiber, eating two slices of whole wheat bread is really little different, actually worse, than drinking a can of sugar-sweetened soda or eating a sugary candy bar.
This information is not new. A 1981 University of Toronto study launched the concept of glycemic index, i.e., the comparative blood sugar effects of carbohydrates: the higher the blood sugar after consuming a specific food compared to glucose, the higher the glycemic index (GI). The original study showed that the GI of white bread was 69, while the GI of whole grain bread was 72 and Shredded Wheat cereal was 67, while that of sucrose (table sugar) was 59.5 Yes, the GI of whole grain bread is higher than that of sucrose. Incidentally, the GI of a Mars bar—nougat, chocolate, sugar, caramel—is 68. That’s better than whole grain bread. The GI of a Snickers bar is 41—far better than whole grain bread.
In fact, the degree of processing, from a blood sugar standpoint, makes little difference: Wheat is wheat, with various forms of processing or lack of processing, simple or complex, high-fiber or low-fiber, organic or non-organic, all generating similarly high blood sugars. Just as “boys will be boys,” amylopectin A will be amylopectin A. In healthy, slender volunteers, two medium slices of whole wheat bread increase blood sugar by 30 mg/dl (from 93 to 123 mg/dl), no different from white bread.6 In people with diabetes, both white and whole grain bread increase blood sugar 70 to 120 mg/dl over starting levels.7
One consistent observation, also made in the original