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In Defense of Carbsby
Linda Johnston, MD, DHt
As libertarians, we are accustomed to holding minority or unpopular opinions. We even pride ourselves on being well and truly out of the mainstream. With that practice under my belt, I have no hesitation in publicly declaring another minority view by standing up in defense of carbohydrates. Al-qaida and bin Laden excepted, carbohydrates currently seem to be public enemy number one, even outpacing the long-standing villain cholesterol. Just as the government always needs to have an enemy, so too do individuals have to have an external enemy to blame for their woes and in this case, their obesity. You can hear it declared far and wide; people are overweight because of carbs! It is certainly not because of overeating, lack of exercise, lifestyle or bad food choices. Outlaw carbs and obesity will vanish! Personally, I am sick and tired of all this mindless carb-bashing and the enormous amount of misunderstanding, misinformation and just plain wishful thinking behind it. For many years I have been a witness to moderate carbohydrate bashing, which usually abates after a time only to resurface a few years later. You remember that several years ago, low-fat was all the rage. The media inundated us with the dangers and evils of every molecule of fat we ingested. Now the wind has changed and the low-carb, high-fat craze has descended on us again. All we hear now is how dangerous the carbs are but it is perfectly okay to eat as much fat as we want. I get a perverse pleasure in witnessing the machinations and gyrations of those previously low-fat proponents trying to explain away their current advocacy of high fat. This recent round of carb-bashing, however, has been more virulent and longer lasting than in previous years. Carbs are taking a beating, and I think it is totally undeserved. How many carb-bashers are just pudgy overeaters who guzzle 4000 calories a day, never walk when they can sit and then blame the carbs. People really seem to think that if only those 4000 calories didn’t come from a single carb, then they wouldn’t get fat! Haven't they ever heard about the First Law of Thermodynamics, which tells us that energy can’t be created or destroyed? This is just one of the many strange notions that pervade people’s ideas about food and carbs. Let’s take a look at what carbohydrates do and dispel some of these false statements about a perfectly good, safe, enjoyable and essential food. I have long observed that most nutritional advice, articles and diet books are authored by people who have little or no background in biochemistry. They may be self-proclaimed nutritionists, social workers, medical professionals, recovered fatties or fellow travelers, yet an essential aspect of nutrition knowledge, the biology and chemistry of the body and metabolism, is usually woefully deficient or, I am sad to say, totally missing. This level of ignorance is quite understandable if you consider some of the fallacious dietary proclamations bandied about under the guise of fact. No one who understood basic biochemistry could possibly make most of those assertions with a straight face. If you can bear with me for a few paragraphs while I give you some basic biochemistry background, I am sure you will also see how unjust this animosity is to a part of our diet that, far from being bad for us is actually a vital and favored nutrient. Foods are divided into three kinds of energy sources: fat, carbohydrate and protein. Protein and carbohydrates each have 4 calories per gram whereas fat has 9. Good health depends on a balance of each so that all functions are performed. Each has certain jobs to do; proteins build structures, carbohydrates provide energy and fats store energy. Although each one can do some of the others’ jobs, the best health is achieved when each performs its own job and is not required by circumstances to do anything else. Proteins build the structures of your body, such as bones, muscles, enzymes and other tissues, including white blood cells of your immune system. You don’t store protein for later use. It has to be used when it is eaten or it is eliminated. Your body is made of protein, and although it can be used for fuel if necessary, being a storehouse is not its primary job. There are times when protein is used for fuel and that is discussed below. Carbohydrates are your fuel and are metabolized to give you energy. All tissues, from bones to muscles to nerves, use carbohydrate as their first choice for making energy. Some carbohydrate is stored in the muscles to be on hand for immediate use. The majority, still only a total of about 1500 calories, less than a day’s worth, is stored by the body in the liver. It is use of this supply of fuel that allows you to go some number of hours without eating. Only that small amount of carbohydrate is stored because it is a very bulky molecule and inefficient to store. Fat is a much more efficient way to put energy into storage and that is its main job. Not only does fat have over twice the number of calories per gram, the molecule itself is smaller and more densely packed than carbohydrate, which is always surrounded by bulky water molecules. Fat allows the body to store more calories in a much smaller space. It is the loss of that water stored with carbohydrate that accounts for the rapid weight loss in the first week of a diet when those carbohydrates and not stored fat are being used for fuel. Once stored, it is difficult to take fat out of storage and use it. The body does not want to use up this supply, preferring that you eat more calories in the form of carbohydrates for your energy needs. This is one reason why dieting is so hard; the body does not want to use up its fat stores. All cells in the body require fuel and can use all three of the different foods groups to supply it. There is only one exception and it is a very important one. The nervous system, including the brain, can only use carbohydrates for fuel. The brain has a very high metabolic rate. It is only about 2% of the body’s weight yet in the resting state it uses up to 20% of the total body energy expenditures. That translates into about 140 gram of carbohydrate per day for the brain alone. Few people realize that carbs are brain food! Another important aspect of metabolism is that carbohydrates can turn into fats for storage, proteins can turn into fats for storage, proteins can turn into carbohydrates but fats cannot be turned into carbohydrate or proteins. Once carbohydrates or proteins have been changed into fats, they cannot change back again. Those calories have to be burned off as fats, which is very hard to do. In addition to the job of providing fuel and being the exclusive fuel source for nerves and the brain, carbohydrates have another critical job. Carbohydrates are a necessary part of the machinery that metabolizes fats. Without adequate supplies of carbohydrates, you can’t burn fats as fuel. Our nutritional and metabolic system has developed over millions of years for our advantage and survival. Diets are a relatively recent phenomena, a mere blink of the eye in the context of the evolutionary time line. Diets, or more accurately speaking, the lack of food, have always been called starvation and considered a very bad thing. It is so bad that the body has developed uncompromising internal mechanisms to keep the body functioning even in the face of a deficiency in its food supply. These include making it very difficult to use more calories than one takes in. We may wish it were easier to shed pounds, but biologically it has been to our distinct advantage that it is not easier. For one thing, as long as people have lived on the planet, even to this very day, for most of the world’s population starvation is the rule and not the exception. Inadequate food is a much more pressing issue for the body to cope with than the plea by those in affluent societies for easy and rapid weight loss. With these basic building blocks of energy metabolism, we can better understand what happens when someone decides to diet and what happens when they choose the popular low-carbohydrate, high-fat diet. Let’s look at what happens to the body when there is a lack of food, whether intentional as with dieting or because the crops failed or the hunters couldn’t snag that bison. A little while after a meal, the stored carbohydrate in the liver is used to meet the body’s ongoing need for fuel in general and the brain’s need for carbohydrate in particular. Although there is nearly a day’s worth of carbohydrate stored there, after a small portion of that is used up, an alarm is raised. Since carbohydrate is essential for the brain, nervous system and to operate much of the machinery of metabolism, the body takes action to guard against those precious carbohydrate stores from falling too low. What does it do? It does a very simple thing: it will make you so hungry that you eat more carbohydrate. For the body, that is preferable to using up the stored supplies. The longer since your last meal, the more your body insists that you ingest some carbohydrate right away. It is pretty simple; the longer you go without eating, the hungrier you get. We have all been unwilling participants in that experiment. Furthermore, the hungrier you are, the more urgent the need is for immediate food and therefore the more likely you are to eat foods that will give your body carbohydrates quickly, such as refined sugars, candy, cookies and other sweet foods. Vilifying and suppressing these kinds of sugar cravings is like telling a drowning man to stop yelling so loud and put his request in writing. If you still don’t or can’t eat, other changes take place. The first line of action is for the body to continue to drive you to eat something hence the stories people in war time countries out of desperation eating grass, paint, paper, dirt, leaves and other indigestible things. As time goes on, you get more and more hungry, and then other signs and symptoms occur. Most people get irritable, headaches, dizziness, extreme weakness, shaky and trembling feelings, sleepiness and even fainting. If food is still not supplied or supplied in an amount too small, then the fuel stored as either fat or protein is used. Fat is used by activating the preferred fat-burning metabolic pathways, but this can be limited if there is not enough carbohydrate to run that mechanism. Protein can also be used for fuel, but recall that protein is not actually stored awaiting use for fuel as fat is. The protein supplies in the body are in the form of muscle and other tissues and to use this fuel your body has to break down those tissues. This is like using the wood your house is made of to stoke the furnace. Burning protein to obtain carbohydrates also occurs to provide the necessary carbohydrates for the brain and to run the fat burning machinery. All in all, you can’t lose fat without having carbohydrate to do it, whether those carbohydrates come from your diet or your muscles. Because your brain can only use carbohydrate for fuel and its functions are so critical, other protein-based biologic functions are sacrificed to provide the brain fuel. To use protein as fuel, first it is chemically changed into a carbohydrate molecule by removing a nitrogen atom. In other words, when you don’t eat enough carbohydrate, your body makes carbohydrate for you. It takes about 100 grams of protein to produce 57 grams of carbohydrate. Your body turns the $15 per pound beef steak you ate into a 79c per pound potato and only at about 57% efficiency. If effect, those advocating low-carbohydrate, high-protein diets are asking you to pay $26 a pound for potatoes. It doesn’t make that much sense to me, but millions of people are doing it. What is the real cost of that pound of beefsteak? It takes about 14–21 pounds of protein from other food sources for a cow to produce one pound of meat protein for you to eat. When you eat that meat only to have it used as a carbohydrate, you are really wasting 25–37 pounds of protein for each pound of carbohydrate. Very few societies have ever been so wealthy as ours to accommodate that kind of flagrant waste of food resources. As the body removes the nitrogen from the protein to create the carbohydrates, it now has to contend with getting rid of that waste product. The kidneys take that nitrogen out of the blood stream and excrete it in the urine. Although designed to process normal amounts of nitrogen excretion, this extra load from increased protein break down puts a strain on the kidneys. One of the long-term problems of consistent high protein, low carbohydrate diets is kidney problems. What about getting rid of the fat? That is what most people want when they start weight loss diets. Fat will be used as fuel when the body is forced into it by a drastic and long-term reduction in calorie intake, not carbohydrate reduction but calorie reduction. When there is not enough carbohydrate to fuel the fat burning metabolism, fats are metabolized in an alternate metabolic pathway, which incompletely metabolizes the fat. This means that the fat produces some calories for fuel and some calorie-containing by-products called ketones, which are excreted in the urine without having to use those calories. That may seem to be the dieters dream – not having to use up all the stored calories from fat while still getting rid of them. If it were only that easy! Ketones are a group of chemicals that include acetone. You know what acetone is. In fact, you probably have a container of it in your garage. It removes paint or fingernail polish, dissolves grease and is a great all purpose solvent. The price for urinating out those few extra calories is having this powerful organic solvent circulating in your blood stream. Naturally your body doesn’t want ketones hanging around and you should not either. They cause symptoms of thirst, dry mouth, irritability, dehydration, weakness, loss of appetite, confusion and if plentiful enough, even coma and death. The appetite depressing action of ketosis is lauded as an additional weight loss benefit of this condition. During the first 6 weeks of starvation, (I mean low carb dieting), the protein destruction remains upward of 100 grams, (3 1/2 ounces) a day. Without another protein source, at that rate, the average-sized person could only survive for about 30 days, even with large fat stores. To prolong survival, the body makes an adaptation whereby it increases ketone-metabolizing processes in the brain enabling it to use ketones for fuel. This results in a reduction of such rapid body protein use, which now reduces to about 15 grams per day. There is great resistance in the body to make this transition to ketone metabolism, which will only occur after 6 weeks of significant protein breakdown and muscle loss. It is a last resort to keep a starving person alive longer. Enough dietary protein can curtail the brain’s increased ketone metabolism. All these factors, in part, account for the difficulty most people have in sustaining their weight loss program up to and beyond this 6-week mark. With this all in mind, many formerly high-protein, low-carbohydrate diets are now advocating eating enough carbohydrate to prevent protein destruction. Such diets are called the protein-sparing, low carbohydrate diets. These diets are usually still far too low in carbohydrate to completely prevent protein break down. Most allow about 60 grams of carbohydrate a day and we have already seen that the brain alone daily requires about 140 grams. Overall muscle mass determines the amount of calories a person uses as their basal metabolic rate. The more muscle, the more calories burned per hour. The more muscle, the more active a person is, and therefore even more calories are used. Muscle breakdown to make the carbohydrate that person has refused to eat results in less muscle and therefore less calorie use. All this is the result of dieting, despite the fact that increased calorie usage was the whole point. I hope it is more apparent now how essential carbohydrates are. They are the ultimate brain food, they protect your muscles, they give you energy to carry on the activities you want to do every day and they taste great!!! What more could we want? What about weight loss? Of course it is possible to lose weight without endangering our brain, muscles and health. The diets for this are not flashy, chic or popular, never have the cache of fad or celebrity diets and rarely, if ever, make the news or the cover of People Magazine. Common sense is rarely lionized. You already know how to lose weight, but it is a dull, practical method that takes effort and discipline. You eat sensible meals of normal sized portions following a calorie restricted, food group exchange model, like the American Diabetic Association or Weight Watchers diets programs along with a consistent exercise program. That is it and nothing that you didn’t know before. This approach results in a slow and steady weight loss, but also gives you a healthier heart, muscles, blood vessels and a longer life expectancy. Certainly carbohydrates are restricted, but only as a part of an overall calorie restriction and not to such a low amount that health is endangered. Medical research studies verify that people who lose weight this way, keep it off longer and more consistently than with the low carbohydrate diets. Studies also indicate that weight loss with the low carbohydrate diets can be faster in the short term but in the long-term, there is no advantage but there are many health concerns from the prolonged high fat intake.
April 10, 2004
Copyright © 2004 by Linda Johnston, MD, DHt
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Carbohydrates
are not the villain of obesity, bad health or even being mildly
over weight. They are a vital part of our daily diet. As in all
things, too much of anything is not good. I hope I have shown you
that too little of something can also be as grievous. As always,
everything is best in moderation! In my defense of carbohydrates,
I am not giving license to gorge on cookies and pasta. I am, however,
giving you enough understanding of your own metabolic mechanisms
to question the bad press heaped on carbohydrates. So go ahead and
enjoy that piece of whole grain bread, not 5 or 6, but one. Enjoy
a small dessert on a special occasion. Get up and move around so
your body can put those carbohydrates to work fueling your muscles,
as they were designed to do. Most of all, take some of your inordinate
preoccupation with your food, diet, carbohydrate count and use it
to read a good book, create some art work, share time with a loved
one and simply live your life.
