The Obesity Code, page 17
Figure 16.1. Glycemic load values for some common foods.
Refining significantly increases the glycemic index by purifying and concentrating the carbohydrate. Removal of fat, fiber and protein means that the carbohydrate can be digested and absorbed very quickly. In the example of wheat, modern machine milling, which has almost completely replaced the traditional stone milling, pulverizes the wheat into the very fine white powder we know as flour. Cocaine users will know that very fine powders are absorbed into the bloodstream much faster than coarse grains—that’s what allows for higher “highs,” both for cocaine and for glucose. Refined wheat causes our glucose levels to spike. Insulin levels follow.
Second, refining encourages overconsumption. For example, making a glass of orange juice may require four or five oranges. It is very easy to drink a glass of juice, but eating five oranges is not so easy. By removing everything other than the carbohydrate, we tend to overconsume what is left. If we had to eat all the fiber and bulk associated with five oranges, we might think twice about it. The same applies to grains and vegetables.
The problem is one of balance. Our bodies have adapted to the balance of nutrients in natural food. By refining foods and only consuming a certain component, the balance is entirely destroyed. People have been eating unrefined carbohydrates for thousands of years without obesity or diabetes. What’s changed, and recently too, is that we now predominantly eat refined grains as our carbohydrate of choice.
WHEAT: THE WEST’S GRAIN OF CHOICE
WHEAT HAS LONG been a symbol of nutrition. Wheat, along with rice and corn, is one of the first domesticated foods in human history. Yet these days, what with gluten sensitivity and obesity, wheat does not have a friend to call its own. But how can wheat possibly be so bad?
As discussed in chapter 9, wheat has been cultivated since ancient times. But by the 1950s, Malthusian concerns of overpopulation and worldwide famine arose again. Norman Borlaug, who would later win the Nobel Peace Prize, began experimenting with higher-yield wheat varieties, and thus was born the dwarf-wheat variety.
Today, an estimated 99 percent of all wheat grown worldwide is dwarf or semi-dwarf varieties. But where Dr. Borlaug bred naturally occurring strains together, successors quickly turned to new technologies to enhance mutations. The new varieties of wheat were not tested for safety, but were merely assumed to be safe in this new atomic age.
It is clear that the dwarf wheat varieties of today are not the same as those fifty years ago. The Broadbalk Wheat Experiment2 documented the change in nutritional content over the last half century. Even as grain yields skyrocketed during the Green Revolution, the micronutrient content plummeted. Today’s wheat is simply not as nutritious as in previous generations. That surely cannot be good news.
Another clue to wheat’s changing character is the enormous increase in the prevalence of celiac disease, which is a reaction against gluten protein that damages the small intestine. Wheat is by far the predominant source of gluten in the Western diet, often by a factor of 100 or more. By comparing archived blood samples from Air Force men over a period of fifty years, researchers discovered that the prevalence of celiac disease appears to have quadrupled.3 Could this be a result of new wheat varieties? This question has not yet been satisfactorily answered, but the possibility is troubling.
Processing methods have changed significantly over the centuries. Wheat berries were traditionally ground by large millstones powered by animals or humans. The modern flourmill has replaced traditional stone grinding. The bran, middlings, germ and oils are efficiently and completely removed, leaving the pure white starch. Most of the vitamins, proteins, fiber and fats are removed along with the outer hull and bran. The flour is ground to such a fine dust that its absorption by the intestine is extremely rapid. The increased rate of glucose absorption amplifies the insulin effect. Whole wheat and whole grain flours retain some of the bran and germ, but suffer from the same problem of rapid absorption.
Starches are hundreds of sugars all linked together. Most (75 percent) of the starch found in white flour is organized into branched chains called amylopectin; the remainder into amylose. There are several classes of amylopectin: A, B and C. Legumes are particularly rich in amylopectin C, which is very poorly digested. As the undigested carbohydrate moves through the colon, gut flora produces gas causing the familiar “tooting” of the bean eater. While beans and legumes are very high in carbohydrate, much of it is not absorbed.
Amylopectin B, found in bananas and potatoes, is intermediate in terms of absorption. The most easily digested is amylopectin A found in—you guessed it—wheat. Wheat is converted to glucose more efficiently than virtually any other starch.
However, despite all the concerns discussed in this chapter, observational studies consistently demonstrate that whole grains are protective against obesity and diabetes. Where is the disconnection? The answer, here is fiber.
THE BENEFITS OF FIBER
FIBER IS THE non-digestible part of food, usually of a carbohydrate. Common types of fiber include cellulose, hemicellulose, pectins, beta-glucans, fructans and gums.
Fiber is classified as soluble or insoluble based on whether it is dis-solvable in water. Beans, oat bran, avocado and berries are good sources of soluble fiber. Whole grains, wheat germ, beans, flax seeds, leafy vegetables and nuts are good sources of insoluble fiber. Fiber can also be classified as fermentable or non-fermentable. Normal bacteria residing in the large intestine have the ability to ferment certain undigested fiber into the short-chain fatty acids acetate, butyrate and propionate, which can be used as an energy source. They may also have other beneficial hormonal effects, including the decreased output of glucose from the liver.4 Generally, soluble fiber is more fermentable than insoluble.
Fiber has multiple purported mechanisms of health, but the importance of each is largely unknown. High-fiber foods require more chewing, which may help to reduce food intake. Horace Fletcher (1849–1919) believed strongly that chewing every bite of food 100 times would cure obesity and increase muscle strength. Doing so helped him lose 40 pounds (18 kilograms), and “Fletcherizing” became a popular weight-loss method in the early twentieth century.
Fiber may decrease the palatability of food and thus reduce food intake. Fiber bulks up foods and decreases its energy density. Soluble fiber absorbs water to form a gel, further increasing its volume. This effect helps fill the stomach, which increases satiety. (Stomach distention may signal a sensation of fullness or satiety through the vagus nerve.) Increased bulk may also mean that the stomach takes more time to empty. Therefore, after meals rich in fiber, blood glucose and insulin levels are slower to rise. In some studies, half the variance of the glucose response to starchy foods depended on their fiber content.5
In the large intestine, the increased stool bulk may lead to increased caloric excretion. On the flip side, fermentation in the colon may produce short-chain fatty acids.6 Roughly 40 percent of dietary fiber may be metabolized in this way. One study demonstrated that a low-fiber diet resulted in 8 percent higher caloric absorption.7 In short, fiber may decrease food intake, slow down food’s absorption in the stomach and small intestine, then help it exit quickly through the large intestines—all of which are potentially beneficial in treating obesity.
Fiber intake has fallen considerably over the centuries. In Paleolithic diets, it was estimated to be 77 to 120 grams per day.8 Traditional diets are estimated to have 50 grams per day of dietary fiber.9 By contrast, modern American diets contain as little as 15 grams per day.10 Indeed, even the American Heart Association’s Dietary Guidelines for Healthy North American Adults only recommends 25 to 30 grams per day.11 However, removal of dietary fiber is a key component of food processing. And improving the texture, taste and consumption of foods directly increases food companies’ profits.
Fiber came to public attention in the 1970s, and by 1977, the new Dietary Guidelines recommended we “eat foods with adequate starch and fiber.” With that, fiber was enshrined in the pantheon of conventional nutritional wisdom. Fiber was good for you. But it was difficult to show exactly how it was good for you.
At first, it was believed that high fiber intake reduced colon cancer. The subsequent studies proved to be a bitter disappointment. The 1999 prospective Nurses’ Health Study12 followed 88,757 women over sixteen years, and found no significant benefit in reducing colon cancer risk. Similarly, a randomized study from 2000 of high fiber intake failed to demonstrate any reduction in precancerous lesions called adenomas.13
If fiber wasn’t helpful in reducing cancer, perhaps fiber might be beneficial in reducing heart disease. The 1989 Diet and Reinfarction Trial randomized 2033 men after their first heart attack to three different diets.14 To the researchers’ astonishment, the American Heart Association’s low-fat diet did not seem to reduce risk at all. What about a high-fiber diet? No benefit.
The Mediterranean diet (which is high fat), on the other hand, was beneficial, as Dr. Ancel Keys had suspected years ago. Recent trials such as the PREDIMED15 confirm the benefits of eating more natural fats such as nuts and olive oil. So eating more fat is beneficial.
But it was difficult to shake the feeling that somehow, fiber was good. Many correlation studies, including the Pima and native Canadians, associate lower body mass index with higher fiber intake.16, 17, 18 More recently, the ten-year observational CARDIA Study19 found that those eating the most fiber were the least likely to gain weight. Short-term studies show that fiber increases satiety, reduces hunger and decreases caloric intake.20 Randomized trials of fiber supplements show relatively modest weight-loss effects, with a mean weight loss of 2.9 to 4.2 pounds (1.3 to 1.9 kilograms) over a period of up to twelve months. Longer-term studies are not available.
FIBER: THE ANTI-NUTRIENT
WHEN WE CONSIDER the nutritional benefits of food, we typically consider the vitamins, minerals and nutrients contained. We think about components in the food that nourish the body. Such is not the case for fiber. The key to understanding fiber’s effect is to realize that it is not as a nutrient, but as an anti-nutrient—where its benefit lies. Fiber has the ability to reduce absorption and digestion. Fiber subtracts rather than adds. In the case of sugars and insulin, this is good. Soluble fiber reduces carbohydrate absorption, which in turn reduces blood glucose and insulin levels.
In one study,21 type 2 diabetic patients were split into two groups and given standardized liquid meals, one control group and the other with added fiber. The group that received liquid meals with added fiber reduced both the glucose and the insulin peaks, despite the fact that the two groups consumed exactly the same amount of carbohydrates and calories. Because insulin is the main driver of obesity and diabetes, its reduction is beneficial. In essence, fiber acts as a sort of “antidote” to the carbohydrate—which, in this analogy, is the poison. (Carbohydrates, even sugar, are not literally poisonous, but the comparison is useful to understand fiber’s effect.)
It is no coincidence that virtually all plant foods, in their natural, unrefined state, contain fiber. Mother Nature has pre-packaged the “antidote” with the “poison.” Thus, traditional societies may follow diets high in carbohydrates without evidence of obesity or type 2 diabetes. The one critical difference is that the carbohydrates consumed by traditional societies are unrefined and unprocessed, resulting in very high fiber intake.
Western diets are characterized by one defining feature—and it’s not the amount of fat, salt, carbohydrate or protein. It’s the high amount of processing of foods. Consider traditional Asian markets, full of fresh meats and vegetables. Many people in Asian cultures buy fresh food daily, so processing it to extend shelf life is neither necessary nor welcome. By contrast, North American supermarkets have aisles overflowing with boxed, processed foods. Several more aisles are dedicated to processed frozen foods. North Americans will buy groceries for weeks or even months at a time. The large-volume retailer Costco, for example, depends on this practice.
Fiber and fat, key ingredients, are removed in the refining process: fiber, to change the texture and make food taste “better,” and natural fats, to extend shelf life, since fats tend to go rancid with time. And so we ingest the “poison” without the “antidote”—the protective effects of fiber is removed from much of our food.
Where whole, unprocessed carbohydrates virtually always contain fiber, dietary proteins and fats contain almost none. Our bodies have evolved to digest these foods without the need for fiber: without the “poison,” the “antidote” is unnecessary. Here again, Mother Nature has proven herself to be far wiser than us.
Removing protein and fat in the diet may lead to overconsumption. There are natural satiety hormones (peptide YY, cholecystokinin) that respond to protein and fat. Eating pure carbohydrate does not activate these systems and leads to overconsumption (the second-stomach phenomenon).
Natural foods have a balance of nutrients and fiber that, over millennia, we have evolved to consume. The problem is not with each specific component of the food, but rather the overall balance. For example, suppose we bake a cake with a balance of butter, eggs, flour and sugar. Now we decide to remove completely the flour and double the eggs instead. The cake tastes horrible. Eggs are not necessarily bad. Flour is not necessarily good, but the balance is off. The same holds true for carbohydrates. The entire package of unrefined carbohydrates, with fiber, fat, protein and carbohydrate is not necessarily bad. But removing everything except the carbohydrate destroys the delicate balance and makes it harmful to human health.
FIBER AND TYPE 2 DIABETES
BOTH OBESITY AND type 2 diabetes are diseases caused by excessive insulin. Insulin resistance develops over time as a result of persistently high insulin levels. If fiber can protect against elevated insulin, then it should protect against type 2 diabetes, right? That’s exactly what the studies show.22
The Nurses’ Health Studies I and II monitored the dietary records of thousands of women over many decades, and confirmed the protective effect of cereal-fiber intake.23, 24 Women who ate a high-glycemic index diet but also ate large amounts of cereal fiber are protected against type 2 diabetes. In essence, this diet is simultaneously high in “poison” and in “antidote.” The two cancel each other out with no net effect. Women who ate a low-glycemic index diet (low “poison”) but also a low-fiber diet (low “antidote”) were also protected. Again the two cancel each other out.
But the deadly combination of a high-glycemic index diet (high “poison”) with low fiber (low “antidote”) increased the risk of type 2 diabetes by a horrifying 75 percent. This combination mirrors the exact effect of processing carbohydrates: processing increases their glycemic index but decreases their fiber content.
The massive 1997 Health Professionals Follow-up Study followed 42,759 men over six years, with essentially the same results.25 The diet high in glycemic load (“poison”) and low in fiber (“antidote”) increases the risk of type 2 diabetes by 217 percent.
The Black Women’s Health Study demonstrated that a high-glycemic index diet was associated with a 23 percent increased risk of type 2 diabetes. A high fiber intake, by contrast, was associated with an 18 percent lower risk of diabetes.
Carbohydrates in their natural, whole, unprocessed form, perhaps with the exception of honey, always contain fiber—which is precisely why junk food and fast food are so harmful. The processing and the addition of chemicals change the food into a form that our bodies have not evolved to handle. That is exactly why these foods are toxic.
One other traditional food may help protect against the modern evils of elevated insulin: vinegar.
THE WONDERS OF VINEGAR
THE WORD VINEGAR originates from the Latin words vinum acer, meaning sour wine. Wine, left undisturbed, eventually turns into vinegar (acetic acid). Ancient peoples quickly discovered vinegar’s versatility. Vinegar is still in widespread use as a cleaning substance. Traditional healers exploited the antimicrobial properties of vinegar in a time before antibiotics by using it to clean wounds. Unfiltered vinegar contains “mother,” which consists of the protein, enzymes and bacteria used to make it.
Vinegar has long been used to preserve food by pickling. As a beverage, the tangy, sour taste of vinegar never gained much popularity, although Cleopatra was famously rumored to drink vinegar in which pearls had been dissolved. However, vinegar still retains fans as a condiment for French fries, a component in dressings (balsamic vinegar) and in making sushi rice (rice vinegar).
Diluted vinegar is a traditional tonic for weight loss. Mention of this folk remedy is found as far back as 1825. British poet Lord Byron popularized vinegar as a weight-loss tonic and would reportedly go for days eating biscuits and potatoes soaked in vinegar.26 Other ways to use vinegar are to ingest several teaspoons of it prior to meals, or to drink it diluted in water at bedtime. Apple cider vinegar seems to have gained a particular following, as it contains both vinegar (acetic acid) as well as the pectins from the apple cider (a type of soluble fiber).
There are no long-term data on the use of vinegar for weight loss. However, smaller short-term human studies suggest that vinegar may help reduce insulin resistance.27 Two teaspoons of vinegar taken with a high-carbohydrate meal lowers blood sugar and insulin by as much as 34 percent, and taking it just before the meal was more effective than taking it five hours before meals.28 The addition of vinegar for sushi rice lowered the glycemic index of white rice by almost 40 percent.29 Addition of pickled vegetables and fermented soybeans (nattō) also significantly lowered the glycemic index of the rice. In a similar manner, rice with the substitution of pickled cucumber for fresh showed a decrease in its glycemic index by 35 percent.30
