The Macronutrient Wars
The U.S. Department of Agriculture (USDA) has in the past advised Americans to cut down on fat and eat plenty of complex carbohydrates to prevent obesity, heart disease, and diabetes. On the other hand, more and more doctors and nutritionists are saying that carbohydrates, not fat, cause all of the evils which threaten our health (and some even claim that many Americans actually need to increase their protein consumption). And if that weren't confusing enough, there is yet another school of thought insisting that the ideal diet consists of a perfect balance of the macronutrients (fats, carbs, and proteins), sometimes citing a "forty-thirty-thirty" ratio.
Instead of deciding who is right and who is wrong, let us take a more in-depth look at the macronutrients in question.
Facts about fat
The power of protein
Carbohydrate confusion
Conclusion
There is a reason why the body's preferred store of energy is in the form of triglyceride, a special type of fat; the same calorie store of carbohydrate would take up nearly twice as much space. Triglycerides provide a person with energy between meals, which again is especially crucial for athletes. Fats in the form of phospholipids are essential to the structure of all body cells. A certain amount of body fat is also essential for well-being; women have a higher threshhold of "essential fat" than do men.
Fat is more calorically dense than other macronutrients, which is the main reason that experts in the past recommended cutting fat out of the diet. "Less fat, less calories" may seem to me logical, but this is not always the case. Many fat-free or low-fat products make up the calorie deficit by replacing the fat with simple processed sugars. Reduced-fat peanut butter, for instance, might contain only ten less calories per serving than the full fat version. When we're taking about 190 versus 200 calories in two tablespoons, those ten calories do not really make a significant difference. And not only are healthy fats from the peanut oil being removed, but satiety is lost as well; in other words, you will feel hungry again sooner than if you had allowed yourself the regular peanut butter. And to top it all off, you've just increased your daily intake of empty calories via the added sugar. (Another culprit, as we will soon find out.)
It is also true that dietary fat is more easily converted to body fat and triglycerides than other macronutrients, but that is only if you one is overeating in the first place. And drastically cutting fat out of the diet is asking for major problems. Essential fatty acids (abbreviated as EFAs), cannot be manufactured by the body, and therefore they must be obtained from food sources. Without ample supply of EFAs, the body's basal metabolic rate might actually go down, defeating the purpose of fat restriction for weight control or health. The kind of fat eaten is more important than simply the amount.
Cholesterol has gotten a bad name because high blood levels of the so-called "bad" cholesterol can contribute to the risk of heart disease and a host of other ailments. The labels of "good" and "bad" cholesterol actually refer not to cholesterol itself, but the way in which it is packaged. The low density lipoproteins (LDL) carry more actual cholesterol and triglycerides than do the high density lipoproteins (HDL). This is because LDL is a transport of cholesterol to body cells, and HDL is the package which carries it back from the cells. Contrary to popular belief, dietary cholesterol has little to do with the level of cholesterol in your blood; one's liver, based on genetics, will manufacture the pretty much same amount of cholesterol daily regardless of one's dietary intake of cholesterol (intake of saturated fat is another matter, as we will see in a moment). Plus, eating certain kinds of dietary sterols, such as the lecithin found in eggs, may actually help keep "bad" cholesterol levels down.
Trans-fatty acids (found in margarine, vegetable shortening, and any processed food with "partially hydrogenated [whatever] oil" in the list of ingredients) are probably the only type of lipid which can truly be classified as purely "bad." Trans-fatty acids not only lower HDL or "good" cholesterol, but raise levels of LDL or "bad" cholesterol. Talk about a double whammy! More and more recent studies have shown that trans-fats in margarine are far more dangerous to health than the saturated fats in butter, and recent studies suggest that trans-fatty acids may be more readily turned into body fat than other fatty acids.
Saturated fats, found mostly in animal products and tropical oils (with smaller amounts in other types of fats) are necessary for the liver's production of cholesterol, and it's this exact role which has given saturated fats a bad rap. While some cholesterol is necessary for good health, too much (as can be stimulated by excessive consumption of saturated fat) will clog arteries and set up conditions for a cardiac episode. For now, the USDA still recommends keeping intake of saturated fats at or below ten percent of one's total caloric intake. The types of saturated fatty acids found in flesh foods (e.g. beef, pork, chicken, and turkey) may be more detrimental to health than those found in plant sources (e.g. coconut and palm oil).
Unsaturated fats come in two forms: polyunsaturated fatty acids (PUFAs) and monounsaturated fatty acids (MUFAs). Polyunsaturated fats are great sources of two essential fatty acids, linoleic and linolenic acid. These are the fatty acids from which the body can manufacture all other fatty acids it needs to function properly. PUFAs also are great sources of other omega 3 and omega 6 fatty acids. PUFAs can help lower levels of "bad" cholesterol, although one's need for vitamin E increases proportionately as PUFA consumption increases, and there are some concerns that excessive amounts of PUFAs may also lower HDL, or "good" cholesterol. PUFAs are found in nuts, corn, flaxseed (an especially rich source of omega 3s), soy beans, pumpkin seeds, green leafy vegetables (although the total fat content of these vegetables is extremely small), some fish oils, and wheat germ and whole grains.
Monounsaturated fats are considered the "best fats" by most, and many nutritionists attribute the general good health of peoples living in the Mediterranean region to their high dietary intake of monounsaturated fats, most notably olive oil. MUFAs not only help lower the "bad" cholesterol, evidence shows that they maintain and may even help increase blood levels of the "good" cholesterol. Great sources of monounsaturated fats include olive oil, peanuts, sesame oil, canola, and almonds.
Again, excess body fat is more often the culprit in contributing to health problems than excess dietary fat. But, surprisingly, fat alone does not make a person fat.
No one doubts that protein is essential for health; the word itself is from the Greek for "of first importance." The trouble lies in the fact that no one can seem to agree on how much is needed on a daily basis. Some critics argue that just because there is not an epidemic of marasmus or kwashiorkor in the West does not mean that protein intake is always optimal. The World Health Organization has determined that most human beings need only about 5% of their daily calories to come from protein, as long as total caloric needs are met. While protein needs are determined in large part by activity level and by the types of activities undertaken, even serious athletes probably don't need much more than 8-10% of daily calories from protein.
Proteins and amino acids play a dizzying number of roles in the body. Proteins are essential structural components of every cell in your body (not just muscle). They are used in enzymes which are the cornerstones of body metabolism. They help maintain homeostasis in the body by serving as buffers in acid-base balance and water balance. Proteins help form neurotransmitters which help your brain keep your body going. Athletes and other active people need more protein by sheer fact that their activity level demands that muscle tissues be rebuilt after being broken down during exercise. Athletes also generally use up more protein as fuel during exercise than do sedentary folk.
Amino acids can be stripped of their nitrogen and converted into glucose (a process known as gluconeogenesis, literally "making new glucose") to provide energy if needed. This is generally only done if (1) there is not enough carbohydrate to provide energy or (2) more protein has been consumed than is needed by the body at that time. The fact that nitrogen groups must be removed from amino acids before they can be used for energy leads to increased urea production, and therefore, increased urination and calcium excretion. This has some scientists worried that too much protein can cause dehydration, kidney problems, and osteoporosis. (While there are numerous factors involved in bone metabolism, excess dietary protein is a more prevalent cause of bone loss than is insufficient dietary calcium.)
Another criticism is that high-protein diets may tend to also be high in fat, particularly saturated fat. Some people wisely increase their protein intake by eating nuts, seeds, low fat tofu, other soy products, egg whites, cottage cheese, and leaner cuts of meats and fish, rather than bacon, hard cheese, and fatty meats. Perhaps more important than increasing protein intake, however, is decreasing intake of refined carbohydrates.
Every major civilization of yesterday and today has used a major source of starch as a dietary staple, and the USDA's original food pyramid made grains the large base of the pyramid. Thus it is easy to understand why most layfolk have been confused by the low-carbohydrate craze. Advocates of "low-carb" diets almost always cite that the real culprit is not carbohydrate per se, but rather, the body's hormonal reaction to eating a high-carbohydrate meal. To understand this, one must understand how your body maintains blood sugar levels.
Eating a meal -- any kind of meal -- will cause blood sugar levels to rise. When blood sugar goes beyond a certain point, a gland called the pancreas secretes the hormone insulin. Insulin plays a number of roles in the body; among them, pushing blood glucose into body cells for them to use it as fuel. This causes blood glucose levels to drop. When these levels fall below a certain point over time, the pancreas kicks in again, this time producing a hormone known as glucagon, which raises blood sugar levels again as needed. Even between meals, insulin and glucagon work in concert to constantly provide energy to hungry cells, including those in the brain and muscles. Without this balancing system brain cells, which require a constant supply of glucose, would quickly perish.
But, as with other hormones, insulin and glucagon do more than just play around with blood sugar. When blood glucose levels get exceptionally high, particularly if there is more glucose running around than the body needs at a time, insulin pushes any excess into the liver and muscles for storage as glycogen. However, the human body doesn't like to store too much carbohydrate; remember, the preferred storage method of energy is in the form of triglyceride. The liver can only store about 100 grams (~400 calories worth) of carbohydrate, and muscles can't store too much more than that. Besides that, glycogen stored in individual muscles is not available to the rest of the body; only liver glycogen can be broken down for use by the brain. Excess glucose beyond that which can be stored as glycogen is converted into triglycerides and stored in the body's adipose tissue. Insulin deals another blow to the system because it stimulates the body to store fat while preventing the body from going into fat stores for energy; excess insulin in the blood interferes with glucagon's work. In fact, without insulin, your body wouldn't be able to store fat very efficiently at all. Too much insulin over time additionally can cause insulin resistence, obesity, high blood pressure, and diabetes.
Of course, it must be noted that insulin is not all "bad." Insulin pushes blood amino acids into the muscles, contributing to muscle growth and development. Without insulin, the body would not be able to push food into cells, and would quickly perish. The problem lies in too much insulin being sent into the blood at one time, as can happen when eating large amounts of refined carbohydrates such as table sugar, white breads, refined grain pastas, and certain high-starch vegetables. What low carb gurus may or may not include in their books is that a huge amount of insulin can also flood the system after eating a heavy meal consisting mostly of protein and/or fat. You won't feel the huge difference in blood sugar, but the effects of the insulin are still the same.
Certain types of carbohydrates will raise blood sugar more quickly than others. More and more dietitians and nutritionists are starting to believe that, as is the case with lipids, the kind of carbohydrate you eat may even be as important as how much, and perhaps even more so. But it's not a matter of simple and complex carbohydrates; potato starch actually is a worse culprit than fruit sugar. For more information on this, see this page on the glycemic index and glycemic load.
To their credit, even the strict induction phase of the Atkins and Protein Power diets emphasize the need for non-starchy vegetables such as broccoli, lettuce, and green beans. Thankfully they also encourage eating all sorts of fruits and vegetables for long-term health maintenance. Many even encourage eating of oatmeal, whole grain breads, and whole grain pastas as long as more refined carbs (such as semolina pasta and white bread) are restricted or avoided. Of course, this is just another way of saying that one's diet should consist mainly of whole food sources of your nutrients.
Overeating any of the macronutrients can cause storage of excess as body fat; it's just that it's far easier to overindulge in refined starches and sweets, and your body's hormones are more apt to react in a way that will store the excess as body fat.
Probably the best answer to the question, "What should I be eating?" is this: Whatever diet helps you to perform at your personal best. When you're not in the competitive season, but still actively training, you might consider "experimenting" with different levels of each macronutrient while keeping total caloric intake within a comparable range. (If you do try out a lower carbohydrate diet, make sure you also drink plenty of fluids, eat an abundance of non-starchy vegetables, and watch your calcium intake. See the main nutrition page for more details.) Some athletes swear by the standard high carb a la Nancy Clark diet, some feel more energy on a lower fat vegetarian regimen, others claim that their performance has never been better since they started raising protein levels and using fruits and non-starchy vegetables to supply their carbohydrate. No matter what, the most important thing is to try and get your nutrition from whole foods rather than overly refined and processed garbage.
In the end, it goes back to everyone's own bio-individuality. So, remember: don't just follow the hype. Eat what you need to fuel your body to perform at your own personal best.
Reviewed 16 May 2006
To contact the author, e-mail ekeraminas@hotmail.com
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