The Body’s Main Fuel
The Body’s Main Fuel
Carbohydrates, both simple and complex, are the body’s main source of energy. They are readily digested and converted into the blood sugar glucose, which fuels the brain and muscles. Without carbohydrates, the body must rely on fats and protein for energy. Fats bum inefficiently in the absence of carbohydrates and leave the kidneys with the burden of excreting large amounts of toxic metabolic chemicals called ketone bodies. These can build up in the blood and cause nausea, fatigue, and apathy, a common effect among those who adhere to the faddish lowcarbohydrate diets.
When protein is used for energy, the body is deprived of this crucial nutrient for building and replacing tissues, and the kidneys have to get rid of the unused nitrogen that’s left over. That’s why on high-protein diets you must drink lots of water to help flush out your kidneys.
Athletes and exercise enthusiasts need a diet rich in carbohydrates to fuel their hardworking muscles. If you exercise vigorously, a high-protein, low-carbohydrate diet can actually be dangerous because it’s hard to take in enough water to meet the needs of your kidneys. Tests of athletic performance have clearly demonstrated an advantage to a high-carbohydrate diet before prolonged exercise. Athletes eating mostly protein and fat scored only half as well as those on a high-carbohydrate diet. Many runners have discovered that pasta is the best supper to eat the night before a race.
Since the turn of the century Americans have cut way back on their consumption of carbohydrates, particularly the “low-prestige” items like flour and cereal grains and potatoes. The falloff has been greatest for the more nourishing complex carbohydrates. It was accompanied by an increase in refined sugars, usually found in foods that are high in calories and low in nutrients.
The net result is that whereas Americans once ate mostly complex carbohydrates laden with important nutrients, now their carbohydrates are mainly the relatively “empty” calories of highly refined and sweetened foods like cakes, cookies, soft drinks, and sugar-coated cereals. (In some of these cereals, sugar is the leading ingredient.) If not for our habituation to the sweet taste, our bodies have no need for sugar, as long as they’re provided with starch for fuel.
In 1977 the Senate Select Committee on Nutrition and Human Needs recommended a sizable increase in our consumption of carbohydrates – particularly the complex starches and naturally occurring sugars in fruits and vegetables. These should claim a 60 percent share of our daily calorie intake, the committee recommended. Other experts go even higher – to 70 or 80 percent carbohydrates. Currently carbohydrates represent 45 percent of the calories in the typical American diet, and more than a third of those calories come from low-nutrient refined and processed sugars. Most Americans eat their weight in sugar every year.
The committee suggested that we replace some of the animal fats in our current diet, which have been linked to a high risk of heart disease and certain cancers, with more innocuous and nutritious carbohydrates. Since the average American already eats twice as much protein as is really needed, and since most of that protein comes laden with saturated animal fats and cholesterol, many nutritionists believe we would be better off if we replaced some of those protein foods with complex carbohydrates.
In most countries where heart disease is rare, the people derive between 65 and 85 percent of their calories from carbohydrates, mainly whole grains and tubers. Contrary to popular belief, diets high in complex carbohydrates have been shown to reduce the insulin requirements of diabetics and may help stave off the artery-clogging diseases to which they are especially prone.
Complex carbohydrates and fruits can also replace processed sweets, such as baked goods, candy, and soft drinks, which contribute to tooth decay and obesity and add little of nutritive value to the diet. Alcohol, which the body processes as a carbohydrate (yielding 7 calories to the gram, as opposed to 4 per gram of regular carbohydrates), is another source of nutritionally empty calories.
The complex carbohydrates are the only major nutrients not associated with any long-term health risks.