Nutritional Anthropology

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Chapter 4
The Science I— Population Studies and Biochemical Clues

In the last chapter, we thoroughly reviewed how we have arrived at our present food supply. We often focus on the changes that have occurred in living memory and, indeed, the pace of change has accelerated in just the last 50 years

However, our lengthy exploration demonstrates how, over a very long period of time—more than 11,000 years—our food supply has been steadily, subtly, and imperceptibly changing. We can see that the way we eat today is radically different in nature from the way humans fed themselves for eons on the savannas of east Africa

How much does this matter? In chapter 3, we outlined some of the consequences of these differences but without going into detail. We will now go into justifying these assertions based on scientific evidence. As each piece of the jigsaw slots into place, we will see how this evidence completes the gaps in the “Owner’s Manual.”

 We begin by looking at scientific studies on human populations around the globe and investigate how their diets affect their health and life span. Such studies are known as population studies, although scientists often use the term epidemiological studies. Then, we will look at the way our biochemistry is supposed to work and what this tells us about the foods we should be eating. In the next chapter, we examine the way nature has designed our digestive system to work. Finally, we will look at what our modern diet is doing to us. Along the way, we will discover insights to thought-provoking conundrums such as how the Eskimo, with a massive calcium intake, suffers from osteoporosis or how the long-lived and healthy Okinawans nevertheless suffer unusually from senile dementia

POPULATION STUDY CLUES
 Humans fanned out from Africa some 60,000 years ago until, by 15,000 years ago, they had ventured to all the major parts of the planet. In this way, this tropical creature, Homo sapiens, now lives in places that are not tropical. Moreover, these groups were obliged to live on what was locally available, so humans all over the planet were now consuming new foods in new ways.

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 Today, the planet is like a huge laboratory with experiments going on in different parts. It is an ideal opportunity to study statistically how different lifestyles affect health and longevity. If a scientific research institution were to propose such an experiment today, the authorities would reject it as being cruel and unusual. However, nature and history have combined to perform the experiment for us, so we can learn from this wonderful resource. Let’s look at some examples of interesting populations to see how their diet has changed from the Savanna Model and the effect it has had on their health

Life Expectancy and “Health Expectancy”
 A good starting point is to examine countrywide statistics for death rates and the reasons for death. National governments collect these figures and international bodies like the World Health Organization collate them. Life expectancy is the factor that is most often paraded as an indication of how well a country is doing. The figures most bandied about are for life expectancy at birth. This means, on average, for every baby born, the number of years it might be expected to live

In Pleistocene times, or even with the San, 30% of babies would die within the first year. This drags down the averages for life expectancy at birth, particularly in the underdeveloped world. For this reason, researchers often look at life expectancy at a later age, often at age 15. This gives the average number of years a 15-year-old is expected to live. This produces some surprising and useful results: we find that once an individual from a poor country has made it safely to 15 years old, he or she can expect to live as long, or even longer, than their counterparts in industrialized societies

For example, 15-year-old boys can expect to live to the age of 76.5 in Japan, 75.6 in Greece, 75.3 in Hong Kong, but only 72.9 in the United States [1]. Women live longer than men in all countries and the proportions are similar: 15-year-old girls can expect to live to the age of 82.4 in Japan, 80.9 in Hong Kong, 80.5 in Greece, but only 79.6 in the U.S. The Japanese overall have the longest life expectancy in the world, closely followed by people living in Hong Kong. Even

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if we take life expectancy at birth, Chinese boys born in the Shanghai province have a life expectancy of 75.7 years, while American boys at birth have a life expectancy of 71.8 [2]. Shanghai baby girls can expect to live for 79.2 years, but American baby girls can only expect 78.6 years of life

The information gets even more interesting as we drill down to find out what diseases are prevalent in a country and what diseases their populations die of. Deliberately, we go back in time to sample the conditions when people’s lifestyles were much more traditional. For example, in 1960, for every 100,000 men, 466 Americans died of heart disease, whereas only 48 Greeks died of it.

Greeks were five times more likely to die of a stroke than an Egyptian. Britons were 1.5 times as likely to die of cancer as a Yugoslav [3]. In 1978, Norwegian women were five times more likely to suffer a hip fracture than a Spanish woman [4]. In 1954, Japanese women had a very low incidence of breast cancer— just 4 deaths per 10,000—compared to 18.5 deaths in the U.S.; an American man was 20 times more likely to die of prostate cancer than a Japanese man [5]. There is little correlation between health and wealth. Japan and the U.S. are both rich countries, but poor countries can be healthy too. In 1978, Albania was the poorest country in Europe with an annual income of only $380 per person. In spite of that, an Albanian man was half as likely to die of coronary heart disease as a British man.[6]

 There is another often-used measure of well-being known as “health expectancy”—this is the number of years that a person can expect to live “in full health.” Based on this measure, the Japanese have the highest health expectancy of 74.5 years [7].  In comparison, the British come in 14th with 71.7 years and Americans come in 24th with only 70.0 years. In other words, you die earlier and spend more time disabled (on average] if you are an American

Statistics like this give us plenty to ponder. What is so special about the Greeks, the Japanese, and the Hong Kong Chinese that they live longer (and in better shape) than Americans? Why are some people more vulnerable to cancers, heart disease, strokes, and osteoporosis than others? There is now a mas-

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sive body of research to identify how different populations’ lifestyles influence their life and health expectancy. We will look at the knowledge obtained for a few populations to see how the evidence builds up. To get the best contrast, we have chosen some extreme cases

The Eskimos
As our species spread out around the world, even the most inhospitable regions were settled. The Eskimos were originally Siberians who got pushed across the Bering Strait by population pressures. They arrived in Alaska 6,000 years ago and found the land already occupied by the American Indians, who had migrated there several thousand years earlier. The only available territory was the land that the American Indians had shied away from—the unimaginably difficult Arctic regions of Alaska and Canada

The Eskimos live in the most extreme of unfavorable environments. It is either cool, cold, or extremely cold most of the time. However, they have no biological special adaptation for these temperatures—the Eskimos are still tropical creatures. They can only live inside the Arctic Circle by insulating themselves from it. This was possible once some Siberian ancestor had worked out how to kill and skin a large furry animal and tailor it into a weather-tight garment. Like astronauts who are obliged to wear spacesuits to work in the vacuum of outer space, so the Eskimos have to cocoon themselves to live in the Arctic cold

The Eskimos’ main activity is hunting and traveling, but they also spend quite a lot of time eating, sleeping, and loafing about [8]. In the depths of winter, just warming up the air they breathe takes 1,000 calories. They eat much of their meat frozen, and that costs their bodies another 300 calories just to thaw it out

Oxford University professor/explorer Hugh MacDonald Sinclair specialized in studying the Eskimo diet, at a time when there were still many Eskimos living the traditional way. In 1953, he estimated that, in winter, the average Eskimo needs to consume about 4,500 calories per day [9]. In Eskimo society, contrary to the Savanna Model, hunting is not a luxury but a necessity. It is virtually the only source of food—at no time is gathering an option as a mainstay. Men are still the driving force in the hunt, although often the women come along and help. Even so, in complete contrast to the Savanna Model, the women and children are highly dependant on their men to feed them. The women are occupied with the domestic chores of skinning the kill, preparing the food, and making clothes and other artifacts

The Eskimo Diet
How did the Eskimos feed themselves? Today, the Eskimo has the double-edged “benefit” of modern civilization, so we have to go back to quite old studies, archives, and records. Anne Keenleyside is a Canadian researcher with special interest in paleopathology, the analysis of ancient bones. She found that, with

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virtually no vegetation in their environment and winter temperatures dropping to below –40°, the Eskimos had to rely almost entirely on animal sources for their food [10]. Dr. Keenleyside and many other researchers have built up a picture of the traditional Eskimo feeding pattern. Eskimos hunted fish, seal, whale, walrus, musk ox, caribou, polar bears, wolves, birds, rabbits, ducks, and geese. They ate every part of the animal—brains, blood, intestines and even the feces. On occasion, the women would gather eggs, crabs, mollusks, and shellfish

The Eskimos were particularly fond of the rather sour contents of the caribou paunch. These are the partly digested remains of lichens and mosses. They cut the blubber off the kill for use as lighting oil and other external uses. They ate most animal food raw, sometimes after considerable putrefaction. Other foods, particularly seal meat, were eaten frozen. Some foods were lightly cooked over a seal-oil lamp or boiled or roasted. Because the Eskimo lives above the tree line, a campfire was a rare luxury fed by dried seaweed and other dried plant remains [11]. In times of plenty, the Eskimo could consume prodigious amounts of meat: 9 pounds in a day has been measured as a normal occurrence. They drank prodigious amounts of water too (we will see why later when we discuss acid/alkali balance)

It was only in the short summer that the Eskimo ate any plant food. The treeless plains of the Arctic have a permanently frozen subsoil, known as tundra, and no plants grow more than knee high. The women would forage for berries, roots, stalks, buds, and leaves. They gathered some kinds of algae and seaweed too. It is estimated, however, that plant food represented no more than about 5% of the diet, even during the growing season

The muscle meat of seal and whale shares similar characteristics with our ancestral wild game—there is little “marbling,” or fat permeating the muscle. The small amount of muscle fat and the visible fat (blubber) are particularly rich in a essential fatty acids (EFAs), notably one called eicosapentaenoic acid (EPA). Later in this chapter, we’ll look at essential fatty acids and their significance to human health

Dr. George Mann, in a report for the U.S. National Defense Committee in 1962, stated that by eating all the animal parts, the Eskimo obtained enough of the “classic” micronutrients to survive including vitamin C [12]. This might come as a surprise, since we think of vitamin C as only coming from plants. However, the skin and guts of animals like seal and caribou are also rich in this vitamin. On the other hand, the Eskimo diet was very deficient in “background” micronutrients

Calcium consumption was huge—over 2,000 mg per day [13]. Protein intake was very high and the fat and oil intake was high [14]. However, the types of fat are of key importance: the Eskimo diet was very low in saturated fat, high in omega-3 oils, and quite high in cholesterol; there were virtually no unhealthy trans fatty acids. The Eskimos’ intake of fiber, carbohydrates, and sugars was

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almost nonexistent, although they got some glycogen (a kind of animal carbohydrate) from the meat. Canadian researcher Kang-Jey Ho estimates that 50% of energy came from fat, 35% from protein, and 15% from glycogen [15]. Most notably, there was virtually no plant food, no soluble fiber, nor the myriad of micronutrients that only plant foods can provide

Eskimo Health
The Eskimos first attracted attention because of an anomaly: in spite of their high-fat, high-meat diet, they had no cardiovascular disease, thromboses, or strokes; they had low blood pressure and good cholesterol levels [16]. In fact, it was too much of a good thing. Their blood was slow to clot when needed (known as a prolonged “bleeding time”) and they suffered from difficult-to-stop nosebleeds

These discoveries led researchers to find the vital role of the various fatty acids in manipulating body biochemistry. The Eskimos did not suffer from vitamin C deficiency (scurvy) or from vitamin D deficiency (rickets); nor did they suffer from diabetes, appendicitis, arthritis, cancer, or dental caries (cavities)

On the other hand, the Eskimo aged fast: they became wizened and shriveled so that a 50-year-old looked more like an 80-year-old. It is estimated that the average life span was indeed only about 50 years. We can learn something too from their high calcium intake of up to 2,000 mg per day. In spite of this megadose of calcium, the Eskimos suffered from bone demineralization and osteoporosis [17]. Doesn’t this go against all we are told today? This should make us question a major nutritional doctrine—that we have only to swallow calcium by the bucketful to avoid osteoporosis. In fact, good bone health is a very complex matter, easily upset by a myriad of lifestyle factors, of which calcium intake is almost irrelevant. We will see later the chief factor at the root of Eskimo osteoporosis and the lessons it gives us for the Savanna Model

Today, the Eskimos suffer the same fate as other hunter-gatherers who adopt the Western lifestyle: high rates of obesity, heart disease, diabetes, and high mortality. Life expectancy has dropped even lower. Later, we will refer back to these observations to learn how the Eskimo had remarkably good health in some areas and weakness in others

The Japanese
We are all familiar with the so-called staple of the Japanese diet, rice. We say “so-called” because there are two misconceptions about rice. First, the Japanese did not eat that much of it—even as recently as 1998, daily consumption of rice was just 6 ounces. And although rice retains a hallowed place in Japanese hearts, it is regarded as a poor man’s food to be replaced by plant foods whenever possible [18].  Traditionally, the Japanese are Buddhists and, as such, they did not eat animals at all. However, they did eat fish, often raw. By Western standards, it was The Science I 91 a high consumption, around 90 g (3.15 ounces) per person per day (four times as much as the average American). From this, they got a high consumption of fish oil, notably the essential fatty acid eicosapentaenoic acid (EPA). Even so, their overall consumption of fat was very low—no more than 10% of calories— which is much lower than the U.S. Department of Agriculture recommended (but rarely achieved) maximum of 30%

The largest percentage of their fat came from rapeseed (canola) oil. East Asians have cultivated rapeseed for millennia, and the Japanese have used rapeseed oil in frugal amounts for at least 2,000 years. To a lesser extent, they used soybean oil. Consumption of saturated fats, hydrogenated fats, and trans-fatty acids was almost zero

The idea of dairy farming had never reached Japan and dairy products never formed part of their traditional diet. Rice was the staple and other cereals were virtually unknown. The Japanese traditionally did not eat wheat, barley, rye, or oats. And they did not eat potatoes either. So, when we say that Japanese consumption of rice was 6 ounces per day, that is it: no other carbohydrate fillers such as bread, pasta, pizza, or french fries existed in their diet

The Japanese traditionally had to husband their resources and they ate much more sparingly than is our custom in the West. They had a high consumption of salt (from soy sauce) of 14 g per person per day. This is a great deal worse than government recommendations of 8 g per day maximum. The Japanese also smoke a lot: 70% of men and 45% of women smoke some form of tobacco

Japanese Longevity and Health
Japanese men have a life expectancy four years greater than Americans and their health expectancy is 4.5 years longer than Americans. But studies show that this only applies as long as the Japanese stay in Japan. When Japanese migrate to America and adopt the American way of life, including its diet, their life expectancy drops to the American norm and they get the same diseases [19]. This suggests that Japanese health and longevity are not about genes but about the way the Japanese live their lives, notably the foods they eat and do not eat

At home, by a fluke of culture, geography, and luck, the Japanese have hit on a good lifestyle, but even so, it is not perfect. For example, they smoke too much and they consume too much salt. More than in most other countries, the Japanese die of strokes and heart disease. The diet of raw fish means that they absorb the live eggs and larvae of intestinal parasites, so that worm infestations of the gut, virtually unknown in the West, are quite common in Japan

Within the general statistics for Japan are buried even more startling results. The archipelago of Okinawa is remote from the Japanese mainland and its population has an even more enviable record for health and longevity. They have one of the highest proportion of centenarians in the world: their chances of living to 100 are 12 times those of an American

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A study carried out in the remote and tiny Okinawan island of Kohama found that the inhabitants eat even more fish, 144 g (about 5 ounces), and far less salt, about 6 g, per day [20]. They eat seaweed and herbaceous plants and also sweet potato and tofu (soybean curd). They have adopted some Chinese practices from nearby Taiwan, eating some pork and drinking green tea. And they exercise a lot: 95% of the 80-year-olds studied led active lives, working long hours every day in their fish-farming paddies

The Okinawans are a poor people, but even the poorest precinct has better longevity—two years more—than the already stellar performance of Japan as a whole [21]. They have the lowest incidence of cardiovascular disease in all of Japan, even though they smoke the same amount. At age 59, only 8% of the population had high blood pressure, 2.3% had heart disease, and 1.2% had diabetes

These figures are two to three times better than mainland Japan. However, the Okinawans had double the incidence of senile dementia (later, we will find the explanation for this interesting result). In a study of 80-year-olds, 90% were fully functional human beings without any disability; only three had impaired hearing and only four had fading eyesight [22].

The remarkable health and longevity of the Okinawans has generated a number of diet programs. However, as we shall see, it is still not ideal. How do we interpret the eating patterns of a poor, agro-fishing Japanese community? Do the types of fish make a difference? Is the green tea significant? Is their “sweet potato” like our sweet potato and does it matter? As we will see later, these matters have a prime importance

The Cretans
 Similar observations have been made with the peoples of the Mediterranean northern rim. The people of the Greek island of Crete had one of the highest life expectancies in the world, in spite of a hard lifestyle. Indeed, although half a world away, there are many similarities with the Okinawan way of life. The Cretans ate frugally; they ate fish but virtually no meat (just the occasional goat’s meat, as beef was nonexistent); they ate plenty of plant food (notably an unusual salad-green called purslane); and they consumed very little dairy, pastries, or sugars

Unlike the Okinawans, they ate bread—a rough-ground, whole-wheat variety— and they had a moderate fat consumption through the sparing use of olive oil in the kitchen. They also had an extraordinary custom: for the Cretan, traditional breakfast often consisted of a jigger of olive oil downed in one gulp, and that was it until lunchtime. Wine was also commonly drunk but in moderation

These people were poor and complained that they felt hungry most of the time. They were obliged to be physically active on their land until an advanced age. Yet, the Cretans had the longest life span in Europe and their incidence of heart disease, colon cancer, high blood pressure, osteoporosis, and diabetes are all much lower than the peoples of northern Europe and North America

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 American researcher Ancel Keys, who first investigated the fabled Cretan longevity and health in the 1950s, wrote a book about his findings which became popular as the so-called Mediterranean diet [23] But this Mediterranean diet has nothing in common with the kind of meal you will find in an Italian, Spanish, or French restaurant. It contains no spaghetti, paella, pizza, or blanquette de veau; even less does it contain their rich cheeses and cream sauces

With the advance of prosperity and the crumbling of old traditions, the Cretans are now adopting Western eating habits, and their deterioration in health is being documented

Testing the Cretan Diet
In the meantime, the baton has passed to researchers who investigated the Mediterranean diet with well-controlled clinical trials. These trials are studies where large groups of people are divided into two test groups. One group is the “experimental” group: they are given the new diet to eat over several years. The second group is the “control” group: they continue to eat their normal diet. At the beginning of the study, both groups are tested for various health indicators, such as blood pressure, cholesterol levels, weight, and so on. They are then retested at intervals as time goes by. Often these studies go on for five or ten years, during which there will also be some deaths

Thousands of clinical trials have tested various hypotheses about food and how it affects health and life span. The results of such studies give us very clear indications as to what is right for human beings to eat and what is not. Quite understandably, we have not the space here to go into the detail of all these studies. We will therefore cite one powerful example and then give a summary of the overall picture that the collection of studies paints for us.

Under chief researcher Serge Renaud, the Lyon Diet Heart Study involved a group of 606 heart attack patients living in Lyon, France. It was equally divided into a control group and an experimental group [24]. The control group followed the conventional advice of the hospital dietitians based on the American Heart Association (AHA) diet. The experimental group was told to adopt a Cretan type diet: more green vegetables and root vegetables, more fish, less meat, and replace beef, pork, and lamb with poultry, no day without fruit, and replace butter and cream with a special margarine made from canola (rapeseed) oil. Olive oil and/or canola oil replaced all other fats. Moderate wine consumption was allowed.

After 27 months, the experiment was stopped early: members of the control group on the AHA diet were dying at a much faster rate than those on the Cretan diet. There were 16 deaths on the AHA diet compared to just three on the Cretan diet. The AHA group was also suffering a much higher rate of second heart attacks: they had 17 non-fatal heart attacks compared to just five on the Cretan diet.

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It is not as though the AHA diet was bad—it was certainly better than how the patients were eating before the start of the study—but the Cretan diet proved to be exceptionally superior even to the conventional dietary treatment recommended by the American Heart Association. The committee charged with looking after the welfare of the groups swiftly decided to stop the trial early so that the AHA group of patients could benefit from the study’s insights and adopt the Cretan diet if they so desired.

Summary—Population Study Clues
Researchers have carried out thousands of similar clinical studies on a huge range of different dietary factors. It is an exciting story in itself, but it is not the

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purpose of this book to relate them in detail. However, the results of such studies do fill in some important gaps in the “Owner’s Manual.” To save the reader so much detail then, we distill these results into generalized summaries. They highlight the foods linked to disease and the foods linked to health. This is a broad-brush approach, but the circumstantial evidence is pointing strongly to lifestyle patterns close to our ancestral, naturally adapted ones. In order to live in the modern world, we need to understand what to make of this evidence, which is the purpose of the latter part of the book.

HELPFUL FOODS 

BIOCHEMICAL CLUES
We turn now to the study of the tens of thousands of chemicals that swirl around our bodies. It is also the study of how they are orchestrated into this incredibly complex system that, day after day, makes our bodies function. It is the science known as biochemistry. A knowledge of how human biochemistry operates will provide us with valuable clues as to what dietary factors fuel the system as nature designed it.

With advancing research, we are realizing just how incredibly complex are the workings of the body. It is a classic case of the more we know, the more we realize how little we know. Biochemists call our body’s biochemistry a “chaotic” system in the mathematical sense. That is, it obeys all physical laws, yet the outcome of any particular action is mathematically impossible to predict. The weather is another chaotic system—even if we knew everything about barometric pressure, temperature, and so forth, there is no way of accurately predicting the weather. We now understand that, when we try to intervene in our body’s operations, we can never predict the outcome with certainty either.

There is a myriad of chemical processes going on in the body all the time. It is mind-bogglingly complex, like a three-dimensional chess game. We have to just understand that it is an unmanageable network. A very important lesson is this: an action today will sometimes have the opposite outcome to the same action yesterday; it all depends on what other processes are happening in the body at the same time.

To take one example: a teaspoon of evening primrose oil taken yesterday might calm inflamed joints; today, it might make them worse. What causes this disquietingly unpredictable result? It all depends on what else you have eaten in the last few hours. A glycemic food (one that causes blood sugar to spike abnormally) increases the body’s production of an enzyme called delta-5-desaturase.

This in turn flips a switch: evening primrose oil now makes chemicals that inflame joints rather than calm them. This is just one of a huge variety of inputs for which we cannot second-guess the outcome.

Indeed, this is one of our central messages: we cannot micromanage our body’s operations. However, this is what people are trying to do all the time, and we end up driving a truck through the delicate minuet being danced by our body’s biochemistry. We meddle in things we only partly understand with consequences that can be the opposite of those intended. I call it the Sorcerer’s Apprentice syndrome. In the 1940 Disney film Fantasia, Mickey Mouse knows the magic spell to animate the broom to fetch water from the well to fill up the kitchen sink. However, he doesn’t know the magic spell to make the broom stop fetching water. Result? The broom goes out of control filling up first the sink and then the house with a nightmarish, unstoppable flood of water. The lesson to learn is this: our own body is the best manager of itself—we just have to get out of the way and give it the tools to do the job.

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We have known for a long time that some saturated fats are harmful to the smooth functioning of our bodies. Already, the message has gotten through that old friends like cream, butter, and fatty meat are not to be trusted. Health professionals have been proclaiming for decades that we should avoid them. Recent discoveries are dispelling other myths: cholesterol consumption of itself is not threatening to health; cholesterol only becomes a problem when it attaches itself to the artery walls. Why does it do that? One immediate reason is that immune system cells on one side of the wall are trying to pull the cholesterol molecule through from the other side, and it gets stuck. The question is: what provokes immune cells into doing something harmful like that?

In other words, our biochemistry needs to work to a very specific pattern. It has firmly defined characteristics that provide strong clues to our naturally adapted diet. We will now examine four of them to see how they illuminate our understanding of the “Owner’s Manual”: blood sugar control, essential fatty acid hormones, the salt/potassium ratio, and the acid/alkali balance.

Blood Sugar Control and Carbohydrates
 People generally understand that carbohydrates are starchy foods like bread, pasta, potatoes, cookies, and cereals. Technically, however, the term carbohydrate is much broader: it also includes a whole spectrum of vegetation (such as lettuce, broccoli, and apples) to starches and sugars (such as sugar itself, honey, confectionary, and maple syrup). In fact, carbohydrate molecules are nothing more than glucose molecules strung together in a multitude of different ways.

Most creatures, even carnivores like dogs, are equipped to digest sugars and starches. Our bodies can unzip the starch molecule back into glucose molecules very quickly by using special helpers known as enzymes. Enzymes have the power of speeding up chemical reactions by thousands of times. Other carbohydrates, such as the material that makes plant walls, can take much longer to digest—these are known as “very complex carbohydrates.”

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The body converts all carbohydrates, sometimes quickly and sometimes slowly (according to their type), into sugar (glucose) in the bloodstream. The body needs to maintain blood glucose levels within very narrow limits, which it does by a seesaw mechanism using hormones released by the pancreas. The pancreas is an organ that has many functions: it secretes a wide variety of hormones and digestive enzymes under instruction from other parts of the body.

If blood sugar is low, the brain instructs the pancreas to release the hormone glucagon into the blood. Glucagon is an “unlocking hormone” that instructs the fat cells to release fat, convert it into glucose, and push it into the bloodstream.

In contrast, if the glucose level is too high, the brain instructs the pancreas to release the hormone insulin into the blood. Insulin is a ‘locking up’ hormone that instructs the fat cells to take the excess blood glucose and store it as fat. In other words, excess glucose equals excess body fat.

In a normal glucose reaction, the body carefully masters the rising level of glucose in the blood and brings it under control. There is no abnormal peak of glucose and the level never drops below the normal fasting level. In a bad reaction, we eat a food that gives us a “sugar rush.” The arrival of glucose is too rapid, and the pancreas cannot maintain this orderly processing. Instead, glucose levels spike sharply to overdose levels about 20 to 30 minutes after eating the food. This condition is known as hyperglycemia, and when this happens, nerve endings are killed off and blood vessels are damaged.

The state of hyperglycemia lasts about 30 minutes, during which we do not feel anything special, and then the pancreas catches up. But it overshoots the mark—the pancreas overcompensates and clears too much glucose from the bloodstream. By 2 to 3 hours after eating the food, there is now a deficiency of glucose in the blood. This deficiency, known as hypoglycemia, provokes feelings of drowsiness, dizziness, irritability, exhaustion, cold sweats, depression, headaches, and a desperate craving for something sugary. Many readers will be familiar with this phenomenon: the mid-morning or mid-afternoon “slump,” which happens a couple of hours after a copious bad-carbohydrate meal.

In this way, abnormally high blood sugar levels mean abnormally high insulin levels. Most Americans are putting their bodies under this kind of stress on a daily basis. This is a biochemical disaster: insulin is a powerful hormone and having it floating around in abnormal quantities (hyperinsulinemia) upsets all other kinds of hormonal reactions.

For example, insulin instructs the liver to make cholesterol. The more abnormal the insulin level, the more abnormal the cholesterol production. The reason most people have high cholesterol levels is not because they are eating it, but because their body is making abnormal quantities of it. In a similar way, abnormal insulin levels provoke abnormal levels of other hormones, which cause abnormal blood clotting (leading to strokes and thrombosis), abnormal clogging and inflammation of arteries, abnormal suppression of the immune

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system (allowing cancers to grow), and even increased sensitivity to arthritis, allergies, and asthma. The problem with hyperinsulinemia is that you do not even feel it. It goes about its work silently and you notice nothing until it is too late—you have the stroke, the heart attack, the cancer, and the sludged arteries. The end result of this abuse of the blood sugar mechanism is often diabetes.

Diabetes is a condition in which one of two things happens: either the pancreas cannot keep up with the demand for insulin and so the insulin production machinery goes into failure or the fat cells stop listening to insulin’s instructions and fail to absorb sugar out of the bloodstream. Either way, there is then an excess concentration of sugar in the blood. Diabetes sufferers, even if medicated, are vulnerable to heart disease, kidney failure, blindness, and gangrene in the feet and hands.

Think of abnormal insulin levels like the iceberg that sank the Titanic. You see very little on the surface, but underneath lurks danger. You just see apparently disconnected peaks—heart disease, thrombosis, artery disease, cancer, allergies, depression, arthritis, obesity—but a looming mass of ice (representing abnormal insulin levels) interconnects them under the surface.

Glycemic Index and Glycemic Load
 Until the 1980s, medical knowledge about how diet affects and controls diabetes was surprisingly imperfect. Then, Canadian researcher David Jenkins developed a breakthrough concept—the glycemic index [25]. He fed various foods to volunteers and measured their blood sugar over a period of time, usually two hours. He then did the same with glucose. Blood sugar is, in fact, glucose and so glucose is thought to be the most “glycemic,” that is, it creates the most powerful sugar rush. Jenkins compared the spikes in blood glucose caused by the test

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foods against the spike for glucose, and the ratio of the two, on a scale of 0 to 100, gives the glycemic index.

The results surprised him and surprised those doctors who took notice. This new way of looking at what carbohydrates do to blood sugar control turned conventional medical ideas upside down. A whole range of foods that doctors thought safe, particularly for diabetics, Jenkins found to be decidedly dubious.

Over the years, researchers have tested many more foods and they found that most processed foods have consistently the same index. However, fresh fruits and vegetables, which are naturally variable, can have quite a wide range of index.

Even so, when all is considered, the glycemic index measure brings completely new insights into what type of foods are right for humans: we now understand that nature did not design the human body to handle foods that give a blood sugar rush.

In this book, foods that have an index in the range of 61 and above, we call “bad” carbohydrates: they consistently produce an unhealthy sugar spike.

Foods with an index between 31 and 60, we call “borderline” carbohydrates: they produce sugar surges which, in a healthy person, the body controls, but only at the price of unnecessary stress to the body. Foods with an index from 0 to 30, we call “favorable” carbohydrates: they produce blood sugar levels that are within the body’s normal range for comfortable, unstressed handling.

CAL GLYCEMIC INDEX 

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Glycemic index scores present a few surprises. Starchy foods like bread (even whole-wheat) and breakfast cereal (corn flakes) are “bad” carbohydrates.

Fruits are all over the place: pineapple is “bad,” banana is “borderline,” and raspberries are “favorable.” Unsurprisingly, non-starchy, non-sugary foods like most nuts, salads, and vegetables fit into the “favorable” category.

Another surprise is the special type of sugar called fructose—it has a favorable glycemic index and does not raise blood sugar levels unhealthily. Fructose is common in fruit, so it is not a surprise that human bodies are very well adapted to it. Fructose is not converted to glucose straight away by the digestive system; it has to pass through the liver for conversion. This slows down the rate at which it hits the bloodstream. Finally, it’s a surprise to find another sugar, maltose, that is more glycemic than glucose itself. Maltose is made of two glucose molecules joined together and, as its name suggests, is the chief sugar in malt.

There is another factor that makes a difference: the concentration of sugars and starches in the particular food. Will just one cornflake or one pineapple chunk set off a bad glycemic reaction? One supposes not, but to find out, some researchers have developed the concept of the “glycemic load.” This is an attempt to define how much of a food needs to be consumed before it triggers a glycemic reaction. They take the glycemic index (GI) of a food and combine it with the amount of carbohydrate in a standard U.S. Department of Agriculture (USDA) serving size to get the glycemic load (GL) score. A GL of 20 or more is “high,” a GL of 11 to 19 is “medium,” and a GL of 10 or less is “low.”

Of course, everything depends on the serving size that is actually consumed by a person. That is why even the concept of glycemic load has its limitations— this factor is only valid if one consumes a standard serving size. The USDA sometimes has absurdly low “normal” serving sizes. For example, a serving of spaghetti is 2 ounces (57 g) of dry weight. Most home cooks use double that quantity when serving spaghetti.

Insulin Index
Measuring the glycemic power of foods is a useful guide and it has a direct bearing on the damage that glucose can do to our health. Nevertheless, it is one stage removed from a worse villain: abnormally high insulin levels. Because of insulin’s potential for creating havoc with our biochemistry, researchers such as human nutrition expert Susanna H. Holt have established insulin indexes for many foods [26]. She did it in a way similar to the process for glycemic indexes: volunteers ate different foods and had their insulin levels measured over several hours.

Insulin indexes usually, but not always, rise and fall in the same rhythm with the glycemic index. Once again, there are some real surprises—some foods that might pass muster on a glycemic basis fail on an insulinemic basis. There is one further factor: proteins might not raise blood sugar levels, but they do raise insulin levels, some very sharply—notably, yogurt. Worse, if proteins and car-

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bohydrates are eaten together, then the insulin raising power of the combination is much greater than of the two ingredients separately.

The table gives some typical values for an insulin index [27]. It can be seen that potato and yogurt are exceptionally “insulinemic”—that is, they have a powerful insulin-raising ability. Beef, fish, and eggs have a normal insulin-raising ability.

Information like this helps build a picture of the foods that we should consider eliminating from the Savanna Model candidates.