Chapter Five - Energy: Less is More
Energy is a topic that concerns us all, every day in every way. Whether you are trying to get the kids off to school or running a marathon, energy is the buzzword that all of us can relate to.
Most of us think of energy in terms of how we feel: "Am I tired?" "Do I have enough energy to finish mowing the lawn, or to make dinner?" Our overall well-being and ability to perform tasks is our individual measure of energy. But what is energy, and how is it created inside our body and in our cells?
These questions are so fundamentally important that we are devoting an entire chapter to discussing them. There are a great many myths surrounding energy production in the body and which foods supply energy. We hope to dispel some of the common themes that surround the dogma regarding carbohydrates and energy.
The most popular refrain for eating large amounts of carbohydrates is that people must consume them in their diet to get energy. Not only is this statement inaccurate, it also is misleading. The body has very specific mechanisms for generating energy. Using carbohydrates is only one such mechanism, and not necessarily the best one.
Furthermore, you do not need to eat carbohydrates to have them available for energy. Your body can make carbohydrates as needed, if the protein supply is adequate. Reducing your daily intake of carbohydrates to 72 grams or less-6 bread units—will result in more energy at your disposal, as long as you eat plenty of fat and protein. Don't just take our word for it: Try it for yourself! Only by direct experience will you appreciate the effects of low-carbohydrate nutrition on your own energy levels.
This chapter is one of the more technical chapters in this book. It may require reading more than once. Our purpose is to dispel some of the many inaccurate statements and old wives' tales that surround the physiology of energy production in people.
Carbohydrates are not required to obtain energy. Fat supplies more energy than a comparable amount of carbohydrate, and low-carbohydrate diets tend to make your system of producing energy more efficient. Furthermore, many organs prefer fat for energy.
Here is a little tidbit that should shake you up.
We have all been led to believe that low-fat diets are heart-healthy. But did you know that your heart primarily uses fat for energy? That's right. Carbohydrates contribute very little to the energy necessary to keep your heart beating, and the preferred fat is saturated fat. Thus, if you eat a high-carbohydrate diet, you are depriving your heart of exactly what it prefers to keep it beating.
If you are not interested in the specific biochemistry of energy production, then you could skip this chapter without losing the main point of the book. We will, however, use some of the principles from this chapter in chapter 10, so we recommend you at least glance through this material. But if you skip this chapter, you will need to accept our point that you do not need carbohydrates to get energy, even the much-touted fast energy.
ENERGY CYCLES
Energy production is a fundamental process required for life. It entails much more than simply having enough energy to walk up the stairs; without proper energy production, your cells cannot divide, all of the biochemical reactions that allow you to function will dissipate, and your body, as an organism, eventually will cease to function.
Energy can exist in many forms, such as heat, light, electrical, and chemical energy, but one of the basic laws of physics stipulates that energy cannot be created or destroyed. It can only he changed from one form to another, ands is how it works for life on Earth.
The overall energy cycle of life is derived from the sun. The sun supplies the initial energy from nuclear fusion reactions that make animal and plant life possible.
Sunlight, one form of energy, gets converted by plants, trees, and shrubs into carbohydrates and oxygen. This process is called photosynthesis. Besides sunlight, photosynthesis also requires carbon dioxide and water. Melvin Calvin and scientists who worked with him during the 1950s at the University of California at Berkeley deter¬mined the many chemical steps that were involved in photosynthesis. Calvin was awarded the Nobel Prize in chemistry in 1961 for his achievements in this area, and now photosynthesis is often called the Calvin cycle.
After making carbohydrates, animals consume the plants, and they use the breakdown of carbohydrates for energy. Carbohydrates also can be stored in animals as fat, which can be used by the other animals who eat them for energy. One by-product from the breakdown of carbohydrates is carbon dioxide, which the animals release into the environment, to be used by plants for photosynthesis. This, then, is the basic energy cycle.
In between the simple steps we just discussed there are many important steps that take place. In the course of this chapter, we want you to become familiar with how animals produce energy, as well as how animal energy production is different from primitive cell organisms. In turn, this information will help to dispel the myths surrounding carbohydrates and energy.
THE ENERGY OF LIFE
The energy used to support life is in the form of chemical energy that, as we have said, begins with the sun. This chemical energy arises from two basic processes. In one process energy, a molecule that supplies energy—food, for example—is oxidized to release energy. In another process, energy is obtained by rearrangement of molecules without oxidation.
Oxidation is a process that removes electrons (negatively charged subatomic particles) or adds oxygen to a molecule. The electrons that are removed from a food molecule are used by some cells to make energy. This process requires oxygen. In other types of cells, a process called fermentation takes place. Fermentation is a series of chemical steps that also yield energy, but this happens in the absence of oxygen, so no overall oxidation takes place.
In both of these processes, a molecule is generated called adenosine triphosphate, or ATP. This is the molecule that has the stored energy in the form of chemical bonds. Figure 5.1 shows the chemical structure of ATP. There are three phosphate groups (triphosphate) bound to an adenosine group. The important parts of this molecule are the phosphate groups because this is where the chemical energy is stored.
When cells need energy for their many different functions, the ATP molecule serves as the supplier by releasing the chemical energy stored within its chemical bonds. However, in order to release this energy for cells to use, the bonds must be broken. Two new molecules result from the bond breakage of ATP. These two new molecules are called adenosine diphosphate (ADP) and phosphate (P). By breaking one of the phosphate bonds, energy is released. This general process is summarized in Figure 5.2. In contrast, the stored energy in food is required to make ATP. This is another energy cycle of life.
The steps involved in making, storing, and using energy require an initial energy source. In the case of animals, this energy source is food. The food molecules get oxidized in the body's cells in order to release electrons from them. These electrons are used to make the ATP molecule, and in turn ATP is used by cells for energy. This is another of the many cycles that take place in life.
It is important to know:
• how different organisms obtain energy
• which food molecules are best for different organisms
• what the requirements are for different tissues and organs for the more complicated organisms
So many people believe, without scientific proof, that carbohydrates are what we need for energy, and that eating more carbohydrates will give us more energy. Yet, most of us have had experiences that suggest this isn't true. That sugary afternoon snack comes to mind—afterward you don't feel so great because energy levels usually decrease after the initial "rush." This is a direct result of low blood sugar from the overproduction of insulin.
So let's take a look at how different organisms create energy, and find out just how important carbohydrates are to humans.
CELLS: PAST AND PRESENT
The Earth is approximately four and a half billion years old. In all that time, only two different cell types have evolved: prokaryotes and eukaryotes. Bacteria were the first cells to live on this planet, and they are the prokaryotes. Higher life-forms marked the beginning of eukaryotic cell development, and eukaryotic cells make up the cells in all animals.
The main difference between these two cell types is that eukaryotes have cellular organelles, and prokaryotes don't. (You may recall the term organelle from biology class. Some representative organelles are the nucleus, ribosome, golgi apparatus, and mitochondria.) Organelles are specialized compartments within eukaryotic cells; they have specific functions and are surrounded by semipermeable membranes to isolate them from other parts of the cell.
Prokaryotes are much simpler than eukaryotes. In prokaryotic cells, there are no specialized organelles. All of the biochemical functions required to sustain life take place inside the cell in a kind of "cell soup," and there is no separation of different components.
The differences between these two types of cells are important because they give us clues about energy production in humans and how that differs from bacterial cell energy production. There also are some important differences in how these types of cells produce energy to sustain life.
ENERGY PRODUCTION IN PROKARYOTIC CELLS
We hope readers are still with us! This background information is essential for understanding the production of energy in human cells and because
it relates to many aspects of cancer that will be pre¬sented in chapter 10. [See for instance "
Can a high-fat diet beat cancer" to get an idea]
Since bacteria, or prokaryotes, appeared on Earth before oxygen was available, they had to produce energy in the absence of oxygen. This is the process of fermentation. Any process that takes place in the absence of oxygen is called an anaerobic process.
Bacteria mainly use glucose as their energy source. Glucose is a six-carbon molecule. The biochemical steps related to breaking down glucose to obtain energy are called glycolysis. The word glycolysis comes from the Greek roots glycos, meaning "sweet," and lysis, meaning "loosening," so glycolysis literally means "the loosening or splitting of something sweet."
The accepted view throughout the biochemical and biological scientific literature is that glycolysis is a primitive process, thought to have begun very early in biological history, before cells evolved to have specialized organelles. However, glycolysis remains a very im¬portant aspect of energy production in advanced life-forms, and oc¬curs in almost every living cell. Most of the decisive work in discovering the glycolytic pathways was done in the 1930s by the German biochemists G. Embden, 0. Meyerhof, and 0. Warburg.
Remember how energy production involves making ATP to be used throughout the cell? The basic steps in turning glucose into ATP involve the splitting, or breakdown, of the glucose molecule into two new molecules, each containing three carbons. One of the products of this breakdown is called glyceraldehyde-3-phosphate. Glyceraldehyde-3-phosphate is the only product from the glucose breakdown that can be oxidized; hence, its metabolism is the key to understanding how ATP is generated from glucose.
Here's how it works: After glyceraldehyde-3-phosphate is formed, a series of metabolic steps involving numerous enzymes convert it into phosphoenol pyruvate (PIT). The phosphate group is removed from PEP at this point to yield another very important molecule, called pyruvate. This is the exact step where ATP is gen¬erated from the original glycolysis of glucose. At this stage, two ATP molecules are generated for every one glucose molecule that was broken down because there are two PEP molecules for every glucose molecule. The ATP molecules can now be used for differ¬ent energy purposes inside the cells.
There are many more biochemical steps in glycolysis that are known to occur, but they are beyond the scope of this book. Still, it's important to at least have a feel for what takes place inside the cell.
Back to pyruvate. This three-carbon molecule has various fates, depending upon what type of cell it's from and what energy needs the cell has.
In one anaerobic reaction, pyruvate gets converted to the mole¬cule lactate. Lactate is an end product of the anaerobic oxidation of glucose. You may already have heard of lactic acid—it's a by-product that builds up in muscle tissue during strenuous exercise.
This occurs because when depleted of oxygen, the cells in muscle tissue begin to make energy anaerobically, just like the cells of bacteria, and they produce lactic acid as the by-product.
The breakdown of glucose to lactate is only one type of fermentation, but it happens to be the simplest chemical fermentation that is known, which is consistent with its designation as a very primitive process.
Another type of fermentation is one that produces ethyl alcohol, otherwise known as the alcohol that you drink. In this process, the six-carbon glucose molecule is broken down to a two-carbon mole¬cule, ethyl alcohol, and a one-carbon molecule, carbon dioxide (CO2). Two ethyl alcohol and two carbon dioxide molecules are formed from every one-glucose molecule. Yeast are the organisms that are used to make the fermentation products that many of us enjoy from time to time.
Yeast are among the simplest eukaryotic organisms, and are ac¬tually very interesting.
One of the reasons yeast use fermentation is for survival. In an overripe piece of fruit, for example, yeast will ferment the sugar deep within the fruit where there is little oxygen, which will generate alcohol. The alcohol kills any bacteria that are present, but the yeast survive. Once the yeast are exposed to oxygen after the fruit decomposes, the yeast can switch and use the alcohol for energy. They're very clever little organisms!
ENERGY PRODUCTION IN EUKARYOTIC CELLS
As time progressed on Earth, plants eventually emerged and began to produce oxygen as a by-product of their metabolism. Other or¬ganisms then adapted to the presence of oxygen, and a major change was made in the way that energy was produced.
Oxygen became the fuel that drives the generation of ATP. Respiration is the name given to the process of obtaining energy in the presence of oxygen.
Everyone knows that we need oxygen to live. This is because
oxy¬gen is used by the body's cells to produce energy by aerobic oxidation.
Eukaryotes produce energy in the cellular organelles called the mito¬chondria. The mitochondria are perhaps the most important organelles in our bodies because they generate almost all of the energy we need to survive. Without them, our cells could not support life.
The proper function of the mitochondria is critical to human health, and carbohydrates and fat play key roles in mitochondrial metabolism. Now we will reveal just how cells produce energy and why carbohydrates are not required as a specific dietary factor in en¬ergy production. We will also take a look at different organs and what their energy needs are. We hope you're beginning to see that there's much more to the story of energy in your body than simply the idea that you need plenty of carbohydrates for fuel.
RESPIRATION AND MITOCHONDRIA
The process of respiration, that is, using oxygen to generate energy, appeared on the Earth after oxygen became available.
Oxygen has the chemical ability to remove electrons from other molecules.
After the atmosphere on Earth became concentrated with
oxygen, cells evolved to use this as a source of oxidation instead of using the fermentation pathway. Eukaryotic cells, present in organisms more complex than bacteria, emerged from these changes. Along with the formation of eukaryotic cells came the evolutionary breakthrough known as the mitochondria.
Mitochondria are the power plants of the cell.
Because they pro¬duce most of the energy in the body, the amount of energy available is based on how well the mitochondria are working. Whenever you think of energy, think of all those mitochondria churning out ATP to make the entire body function correctly. The amount of mitochon¬dria in each cell varies, but up to 50 percent of the total cell volume can be mitochondria. When you get tired, don't just assume you need more carbohydrates; instead, think in terms of how you can maxi¬mize your mitochondrial energy production through respiration.
INSIDE THE MITOCHONDRIA
If you could shrink to a small enough size to get inside the mito¬chondria, what would you discover? The first thing you'd learn is that the
mitochondria are primarily designed to use fat for energy! This is a very important point that we need to examine further.
Mitochondria were specifically designed to use fat for energy.
Exhibit 5.1
'The five major steps in producing ATP within the mitochondria
Step 1 Fuel source transported into mitochondria
Step 2 Fuel converted into acetyl-CoA
Step 3 Oxidation of acetyl-CoA to remove electrons
Step 4 Electrons transported through electron transport chain (or respiratory chain)
Step 5 Oxidative phosphorylation to produce ATP
ATP from the Mitochondria
The complete steps in making ATP within mitochondria are nu¬merous and very complicated, but a look at the five major parts of ATP production will be all that is needed for you to know how en¬ergy is created in our cells. These five steps are summarized in Exhibit 5.1. Each step is discussed in more detail below. Don't get bogged down with the scientific names. Just go with it for a while and you will see how it all fits together. Remember that these chem¬ical steps are taking place thousands of times per second all over your body.
Step 1: Transportation of a Fuel Source into the Mitochondria Since the process of making ATP actually takes place inside the mi-tochondria, the necessary fuel must first be transported there.
The fuel is either derived from glucose or from fatty acids. Fatty acids are the chemical name for fat. They have a charged acidic group on the end of them, which is why they are called fatty acids.
Fatty acids can be saturated or unsaturated.
Fatty acids are transported into the mitochondria completely intact. L-carnitine is the compound necessary to transport medium-and large-sized fatty acids inside the mitochondria from the cell soup (called cytosol). Think of L-carnitine as a subway train that brings people into the city from the suburbs; likewise,
L-carnitine brings fats into the mitochondria.
L-carnitine is chiefly found in animal products. (Its name is derived from the Greek word carnis, meaning "meat" or "flesh.") L-carnitine is one of many very important substances that are only found in appreciable quantities in animal foods,
which is another reason to eat foods derived from animals. We will discuss more of these substances throughout the book, particularly in the chapter on vitamins and minerals.
Once inside our cells, glucose gets broken down by the process of glycolysis, just as in bacteria. This breakdown takes place outside the mitochondria. Two possibilities may now occur. The product from glycolysis (pyruvate) can either move into the mitochondria to be oxidized, or it can be broken down to lactate outside the mitochondria by a fermentative process similar to the one described for bacteria.
To summarize this step:
Fat is transported into the mitochondria as a complete, intact molecule. Glucose gets broken down outside the mitochondria, and the product of this glycolysis (pyruvate) either gets transported into the mitochondria, or it is used anaerobically to produce energy and the by-product lactate.
Step 2: Fuel Is Converted into Acetyl-CoA
After the fatty acids are inside the mitochondria, they are oxidized by a process called beta-oxidation. Remember:
Oxidation means that electrons are removed from a molecule. In the beta-oxidation process, fats are broken down into two carbon molecules. This process releases electrons to be used in step two.
Acetyl-CoA is the direct product from beta-oxidation of fats inside the mitochondria . When pyruvate enters the mitochondria from glycolysis, it must be converted into acetyl-CoA by an enzyme reaction. Acetyl-CoA is the starting point for the next cycle in the production of ATP inside the mitochondria.
Step 3: Oxidation of Acetyl-CoA and the TCA Cycle
The cycle that oxidizes the acetyl-CoA is called the TCA (tricar-boxylic acid) cycle. Electrons are removed from acetyl-CoA, and carbon dioxide (CO2) is generated as a by-product. Carbon dioxide is the oxidized product of acetyl-CoA. Carbon dioxide is the byproduct of mitochondrial respiration, and is eliminated from our bodies through our breathing or through our skin.
Step 4: Electrons Are Transported Through the Respiratory Chain
'Ile electrons obtained from the oxidation of acetyl-CoA, which ultimately came from fats or sugar, are shuttled through many molecules as part of the electron transport chain inside the mitochondria. Some of the molecules are proteins, while others are small, non-protein cofactor molecules.
One of these cofactor molecules is an¬other important substance that is mainly found in animal foods. It is called coenzyme Q-10. Without coenzyme Q-10, mitochondrial res¬piration would be unable to function, and energy production would he minimal.
Step four also is the step where oxygen comes into play. Oxygen accepts the electrons at this stage and is then chemically reduced to water.
Step 5: Oxidative Phosphorylation
As electrons travel down the electron transport chain, they cause electrical fluctuations between the inner and outer membrane in the mitochondria. These chemical gradients, as they are sometimes called, are the driving force that produces ATP in the process called oxidative phosphorylation. ATP is made from ADP and a phosphate molecule (the reverse of its breakdown for energy), just like in bac¬teria. The ATP is transported outside the mitochodria for the cell to use as energy for any of its thousands of biochemical reactions.
These five steps are summarized in Figure 5.3. [see attached image]
WHAT DOES IT ALL MEAN, ANYWAY?
During their evolution, cells developed an organelle that specifically uses fat for energy. This suggests that using fat metabolism for energy production is part of a higher form of life. If there were no mitochondria, then fat metabolism for energy would be limited and not very efficient. Bacteria are able to use some fat for energy, but they prefer glucose and other easily oxidized carbon sources.
[...][sorry, the scanned part of this chapter was unusable. It basically explains the amounts of energy produced from each energy source][...]
ENERGY CONSIDERATIONS IN DIFFERENT ORGANS
The Brain
Your brain uses between 150 and 200 grams of energy daily, mainly from glucose. Since we promote no more than 72 grams of utilizable carbohydrates per day, your body will need to make up the difference.
Fortunately, the body has many ways to do this. The first is a process called gluconeogenesis. This means "the new formation of glucose."
The body can make glucose from amino acids obtained from proteins, or it can start with pyruvate.
The signals to begin gluconeogenesis are sent out when glucose levels in the diet drop to low enough levels and the supply of glycogen in the liver is used up. Gluconeogenesis functions to bridge the gap until energy can be obtained from stored fat. With today's high-carbohydrate food intake, fat usage for energy is diminished. After reducing carbohy¬drates, it can take some time for the body to switch over to primar¬ily using fat for energy.
By reducing carbohydrate intake, the synthesis of glucose from protein is increased. The making of glucose is an anabolic process and requires energy to build up the glucose molecule from smaller pieces. We have already shown that, with adequate fat consump¬tion, large amounts of ATP will be generated in the mitochondria. This ATP can be used for gluconeogenesis.
This new pool of glucose can now be used for energy by the brain and other tissues.
The beauty of this is that the glucose is made on an as-needed basis. This eliminates the excessive buildup of insulin and blood glucose levels that accompany excess carbohydrate consump¬tion. And, as we pointed out in chapters 3 and 4, excessive levels of insulin over a prolonged period of time can have dire consequences.
Many of our detractors have argued that the problem with this philosophy is that the body will use up too much protein, and muscle will wither away. This assertion is based on what is known about starvation. No one can argue against the fact that in times of starvation, the body will weaken and begin to wither away. But
we're not talking about starvation. We're talking about a situation where there is plenty of protein available. After seeing the results of the low-carbohydrate diet on fat and muscle growth in thousands of people, we can confi¬dently assure our critics that no one has ever withered away. On the contrary, in the long run, people either lose fat or gain muscle—even very thin people.
Let's look at it another way.
Would you rather have big muscles to supply protein for gluconeogenesis, or have big fat deposits from carbohydrates and use the stored fat for energy? Even if you choose the fat-deposit scenario, you'll have to reduce your carbohydrates in order to activate the glucagon and epinephrine hormones to burn the fat. There's just no avoiding low-carbohydrate nutrition if you want to obtain optimal health!
Another important, and often misunderstood,
energy source in our cells are compounds called ketones.
Ketones are generated from the breakdown of fatty acids in the mitochondria of liver cells and the addition of two acetyl-CoA molecules. These ketone "bodies," as they are sometimes called, are transported to various tissues through the bloodstream and converted back into acetyl-CoA to generate ATP again.
The presence of ketones in the blood and urine, a condition known as ketosis, has always been regarded as a negative situation, related to starvation.
While it is true that ketones are generated during starvation conditions, they also are generated in times of plenty—but not plenty of carbohydrates. Since carbohydrate consumption suppresses lilt metabolism, ketones do not form. But in the absence of most car¬bohydrates in the diet, ketones will form from fat to supply energy. This is true even if large amounts of protein and fat are consumed in the diet, which is hardly a starvation condition.
Your brain, as well as other tissues, can use ketone bodies for energy. So here again we see that glucose is not necessary for energy, even for the brain. But
Dr. Lutz has found that the benefits of low-carbohydrate nutrition only require 72 grams or so of carbohydrate per day. This amount is not usually low enough to require the body to make ketones for energy. Nonetheless, except in certain cases of people with metabolic diseases, ketosis is not something to fear. [a diet consisting of 90% of fats and proteins and 10% carbs is probably the amount required to be on ketosis, see for instance "
Study finds eating fatty foods can help stop seizures"].
Remember that what is considered a "normal diet" today is based on a limited amount of data, all of which was acquired after humans already had begun eating too much carbohydrate. If you could take a trip back to the days before modern humans emerged, you might very well find that ketosis was more the normal metabolic state, and t hat today's human metabolic state is mostly abnormal.
The Heart and the Skeletal Tissue
It seems that no one really discusses energy in terms of organs other than the brain, which is always quoted as needing glucose. We never hear anything about the needs of the heart and Other organs.
One of the body's best-kept secrets is that the heart uses fatty acids almost exclusively for energy, and these are saturated fat.1'2 This is a truly important point, and we think you can see why.
How can people say that most healthy foods for the heart are low in fat, when the heart muscle is known to require fat in order to beat?
One reason could be that fatty acids can also be made from acetyl-CoA. Using this mechanism, the acetyl-CoA derived from glycolysis can make fatty acids as needed. However, it is known that fatty acid synthesis does not significantly contribute to the energy needs of the heart muscle cells.
The fact is, your heart needs fat from your diet to keep working.
Low-fat diets that are also high in carbohydrate intake are probably the worst thing you could do for your heart, yet this is the prevail¬ing theory, promoted by numerous, often misinformed, organiza¬tions and people.
The single reason that the low-fat diet is so greatly promoted is this: fear of cholesterol. Yet this is but another widespread myth that's not really consistent with available information. The next chapter on heart disease will reveal just how weak the cholesterol theory is.