Neal Barnard, M.D., is a physician, clinical researcher, and adjunct associate professor of medicine at the George Washington University School of Medicine. His books include Breaking the Food Seduction, Turn Off the Fat Genes, and Foods That Fight Pain.
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The Basics Have Changed
In the past few years, much of what we thought we knew about diabetes has been turned on its head. What is now coming into focus is an understanding of its fundamental causes, and that gives us power we never had before.
To make sure we are at the same starting point, let me walk you through the basics: symptoms, diabetes types, and typical treatments as they are currently used. Then I will show you what's new.
HOW DO WE KNOW IT'S DIABETES?
First, let's make sense of the symptoms. Diabetes may arrive with no symptoms at all, but often it starts with fatigue. For no apparent reason, your spark is just no longer there. It may also seem that you are losing water more rapidly than you should be, which is to say that you make trips to the bathroom more often than usual. And you are thirsty: You find yourself drinking a surprising amount of water.
Here is what is going on: The fundamental problem is that sugar is not able to pass from your bloodstream into the cells of your body. From that single problem come a great many others, like one domino knocking over another and another and another.
The sugar we are speaking of is glucose--one of the smallest and simplest sugar molecules. In this case, sugar is not just another word for junk food or empty calories. The fact is that the cells of your body use this kind of sugar--glucose--as an energy source. Like gasoline for your car or jet fuel for an airplane, glucose is your body's fuel. It powers your movements, your thoughts, and more or less everything you do.
And that is exactly the problem. If glucose is unable to enter your cells, they are deprived of their basic fuel, so you lose your energy. That is why you are fatigued. If your muscles do not have the glucose they need for power, you tire easily.
Meanwhile, the glucose that cannot get into your muscle cells builds up in your bloodstream. It becomes more and more concentrated in the blood, and eventually it starts to pass through the kidneys and ends up in your urine.*
Now, as glucose passes through your kidneys, it carries water along with it- -lots of water, hence all those trips to the bathroom. What follows, naturally, is thirst--you are losing all those fluids. So fatigue, frequent urination, and thirst are all symptoms of one problem: glucose having trouble getting into your cells.
You may also find that you are losing weight. And no, this is not an especially welcome event--not in this situation. You lose weight because your cells are in essence starving. Nutrients cannot enter your cells, so your body is malnourished. Yes, even if you are eating plenty of food, nutrients and fuel are unable to get where they are needed.
Every day, people arrive at doctors' offices complaining of fatigue, frequent urination, thirst, and sometimes unexplained weight loss. The doctor takes a blood sample, finds an unusually high level of glucose in the blood, and diagnoses diabetes. The doctor then advises the patient that it is essential to get blood sugar under control. An overly large amount of glucose flooding through the bloodstream day after day can harm the arteries. Left unchecked, it can damage the heart and the delicate blood vessels of the eyes, kidneys, and extremities.
But as we have shown in our research studies, the road to high blood sugar is a two-way street. When you change your diet and make other healthful improvements, a rising glucose level can fall. Sometimes the change can be so dramatic that no doctor looking at you afterward would ever guess that you had once been diagnosed with diabetes.
* The passage of glucose from the bloodstream into the urine led to the technical name doctors use for diabetes: diabetes mellitus. Diabetes comes from a Greek word meaning "to pass through," and mellitus is the Latin word for "honey" or "sweet."
How Doctors Diagnose Diabetes
Doctors diagnose diabetes if:
. You have symptoms of diabetes (frequent urination, unusual thirst, unexplained weight loss) and your blood glucose level is 200 milligrams per deciliter (mg/dl)--(or 11.1 millimoles per liter (mmol/l)*--or higher, regardless of the time of day or whether you are fasting, or . Your blood glucose level is 126 mg/dl (7.0 mmol/l) or higher after an 8-hour fast.
Your doctor will consider this a provisional diagnosis until it is confirmed by similar testing on a separate day. In some cases, doctors perform a glucose tolerance test, in which you drink a syrup containing 75 grams of glucose. If your blood glucose value is 200 mg/dl (11.1 mmol/l) or higher 2 hours later, your doctor will diagnose diabetes.
Normal fasting blood glucose is less than 100 mg/dl (5.6 mmol/l). After a 2- hour glucose tolerance test, the value should be less than 140 mg/dl (7.8 mmol/l). If your values are above the normal limit but not high enough for a diagnosis of diabetes, your doctor will diagnose prediabetes (impaired glucose tolerance), which often precedes an eventual diabetes diagnosis.
* US medical laboratories measure glucose in milligrams per deciliter (mg/dl). In most other countries, glucose is measured in millimoles per liter (mmol/l). As you will see, the same units are used in cholesterol measurements.
A diagnosis of diabetes--or prediabetes--means the insulin in your body is not doing its job adequately. Insulin is a hormone that moves sugar from your bloodstream into the cells of your body, among other functions. It acts like a key, opening a door to the cell, so to speak, and allowing nutrients inside. When insulin arrives at the cell's surface and opens the door, glucose is able to enter the cell, which uses it for power.
If for some reason your body is not making insulin, the result is rising blood glucose levels. Similarly, your blood glucose rises if your cells resist insulin's actions--the key goes in the lock, but the door will not open. Over the long run, high blood glucose levels can damage your nerves, eyes, kidneys, and other parts of your body.
Diabetes comes in three main types, called type 1, type 2, and gestational diabetes. Let's look at each one.
Type 1 diabetes usually manifests in childhood or young adulthood. It used to be called childhood-onset or insulin-dependent diabetes. In type 1 diabetes, something has damaged the pancreas's ability to produce insulin, and you need to get it from an outside source--typically by injection. However, recent research has revealed a great deal about how diet changes can dramatically reduce the risk that diabetes will bring any serious complications your way, as you will see in Chapter 3.
In addition, we know more than ever about the causes of the disease, arming us with more power to prevent it. The damage to the insulin-producing cells is caused by the biological equivalent of "friendly fire." That is, it is caused by the body's immune system--our white blood cells that are supposed to fight bacteria and viruses. These cells ought to protect you, but instead they have attacked the cells of the pancreas, destroying its ability to produce insulin. In Chapter 3, we will look at what triggers this process. It may surprise you to learn that foods--particularly the foods infants are fed within the first months oflife--are leading suspects.
Type 2 diabetes used to be called adult-onset diabetes, or sometimes non- insulin-dependent diabetes. About 9 out of 10 people with diabetes have type 2. Most people with this form of the disease still produce insulin; the problem is that their cells resist it. Insulin tries to bring glucose into the cells, but the cells respond like a door with a malfunctioning lock. In response to these sluggish cells, your body produces more and more insulin, trying to overcome the resistance. If the body's insulin supply cannot overcome the resistance, glucose simply builds up in your blood.
Diabetes drugs work to counteract this problem: Some make your cells more responsive to insulin. Others cause your pancreas to release more insulin into the bloodstream or block your liver from sending extra glucose into the blood.
Until now, most diabetes diets have tried to compensate for the cells' resistance to insulin's action, too. They limit the amount of sugar in your diet. They also limit starch (complex carbohydrate) because starch is actually made from many glucose molecules joined together in a chain. During digestion, starch breaks down to release natural sugars into the blood. The idea is that if you do not get too much carbohydrate at any one time, your cells will not be overwhelmed with too much glucose. For people on medications, typical diet plans aim to keep the amount of glucose or starch fairly constant from meal to meal and from day to day so the amount of medication required to help your body process glucose--your daily dosage- -can stay the same, too. In short, these diets guide you on what, when, and how much to eat.
Insulin is Made in the Pancreas
Insulin is made in the pancreas, an organ located just behind your stomach that is about the size and shape of a TV remote control. In fact, remote control is what the pancreas is all about. It sends insulin into the bloodstream to travel to the cells of your body to help them take in glucose from the bloodstream. In type 1 diabetes, the pancreas has stopped making insulin. In type 2 and gestational diabetes, the pancreas is usually able to make insulin, but the body's cells resist its action.
New research has changed everything, however. We can now use diet changes to influence insulin sensitivity directly. So, as you will see shortly, the nutrition prescription has been completely rewritten to take advantage of this new understanding.
Gestational diabetes is similar to type 2 except that it occurs during pregnancy. While it typically disappears after childbirth, it is a sign of insulin resistance, and that means that type 2 diabetes may be around the corner. With the same sorts of steps that tackle type 2 diabetes, we can often stop gestational diabetes from ever turning into type 2.
GENES ARE NOT DESTINY
Diabetes runs in families, but don't take that to mean that if one of your parents has diabetes, a similar diagnosis has to be your fate as well. You can change things.
Let's take a look at type 1 diabetes first. Many children are born with genes that make it possible for them to develop type 1 diabetes, but most of them never do. In fact, even among identical twins, when one twin has type 1 diabetes, the other has less than a 40 percent chance of having it.1 What makes the difference, apparently, is the environment, particularly the foods the child is exposed to early in life, viral infections, and perhaps other factors.
Genes play a similar role in type 2 diabetes. Many years before diabetes ever manifests, special tests can detect insulin resistance in young adults who have inherited a tendency toward type 2 diabetes from their parents. If they eat the same kinds of foods their parents did, they are very likely headed for a diagnosis. Abundant evidence shows, however, that changes in diet and lifestyle can cut the odds that diabetes will occur. When it does occur, diet can dramatically alter its course.
The point is this: Some genes are dictators, and others are not. The genes for hair color or eye color, for example, really are dictators. If they call for you to have brown hair or blue eyes, you can't argue. But the genes for diabetes are more like committees. They do not give orders; they make suggestions.
If our genes call for diabetes, we do not necessarily have to listen to them. We have more control than you might imagine.
As you have seen, doctors diagnose diabetes based on your blood glucose level, and tracking your blood glucose is an important way to track the effects of diet and medication dosages. As helpful as glucose testing is, though, it really indicates only how you are doing at the time you take the test. The best way to tell how you are doing over the long run is with a test called hemoglobin A1c, or A1c for short. This is the main way you will track your progress in controlling diabetes.
Hemoglobin is the pigment that gives color to your red blood cells and whose job it is to carry oxygen. What the A1c test actually measures is how much glucose has entered your red blood cells and become stuck to hemoglobin. If you have had a lot of glucose in your blood, a fair amount of it gets into your cells and sticks to your hemoglobin. If you have not had much glucose in your blood, your hemoglobin has much less stuck to it.
Since red blood cells have a fairly short life span (about 4 months), the test indicates how well your blood sugar has been controlled over the preceding 3 months or so. The American Diabetes Association (ADA) recommends that people with diabetes get their A1c values below 7 percent. Research shows, however, that lower values cut the risk of complications, so many experts now call for targets of 6.5 or even 6 percent.
If you have diabetes, chances are you were given printed guidelines on what to eat and what to avoid. Perhaps you have met with a dietitian, and you may have been referred to a diabetes class. Unfortunately, most people do not get the ongoing support they need to make dietary changes, and as a result, this well-meaning effort may not have much effect. If you are like many people, you may have found your diet tough to sustain.
For many years, the ADA has offered diet recommendations designed to provide basic nutrition while also keeping calorie intake and food choices reasonably stable over the course of the day and from one day to the next, as you saw above. The idea was that if you had no carbohydrates for breakfast but then had a big carb-fest later in the day, your blood sugar would change erratically. Similarly, if you had lots of starchy foods on Monday but went low-carb the rest of the week, your blood sugar would be all over the map, and your medications could not keep up with you.