Carbohydrates are the breads, cereals, rice, and pastas that form the foundation of the food pyramid, and experts recommend six to eleven servings daily. Typical serving sizes include one slice of bread, one ounce of breakfast cereal, or one-half cup of pasta. Carbohydrates contain the sugars and starches necessary to keep the body running and the fiber necessary to ensure smooth functioning. One gram of carbohydrate yields four calories.The body converts sugars and starches to glucose for energy or glycogen for energy storage. Fiber keeps the intestines running well and helps prevent constipation, heart disease, cancer of the colon, and diabetes. (Do not look down on the lowly bran muffin.) About 60–65 percent of the calories in your diet should be carbohydrates. Contrary to popular opinion, potatoes alone will not make you fat. Only the butter, sour cream, and cheese that make them taste so good do that.One question that always arises regarding carbohydrates is whether an athlete should "load carbos"–eat large amounts of carbohydrates–before a competition when demand on the muscles will be greatest. The idea behind carbohydrate loading is to force the body to store extra glycogen in the muscles so that the glycogen can supply energy in endurance events. People have developed elaborate schemes to turn carbohydrates into muscular glycogen. Most of these schemes include exercising to exhaustion (or fasting) to deplete glycogen stores and then tankingup on spaghetti and other carbohydrates. But fasting or exhaustion exercise can be very hard on the body. It may cause more damage than any possible benefit obtained from loading up afterwards.The food eaten immediately before an event does not generally improve performance–superior performance comes from the dietary and training habits of the past several months.
The meals right before a strenuous competition should not contain high-protein or high-fat foods. They takelonger to digest, they increase the stress on the kidneys, and they may fail to supply the needed nutrients because of demands made on the blood supply by stress and tension on the day of competition. The best meal is one rich in carbohydrates, whether the exercise is to be intense or prolonged. Athletes should allow three hours for proper digestion and absorption of this carbohydrate-loaded meal.
Here are some guidelines:
- Eat solid food three to four hours before the event, or drink a liquid meal two to three hours before. The liquid meal should be low in fat and protein and have some vitamins and minerals.
- Avoid anything that causes gas. You don′t need jet propulsion.
- Don′t eat sweets or sugared drinks within one hour of the event. The insulin they stimulate will eat up the glycogen.
- Be sure to drink enough to stay hydrated.
Foods that build tissue and muscle and repair cells, proteins are the only food compounds that contain nitrogen. When these proteins break down during digestion, they provide the amino acidsneeded to manufacture a seemingly infinite number of special-purpose proteins, including enzymes, hormones, and even structural components of body cells. A protein′s measurement in energy is the same as that for carbohydrates (four calories). The ever-resourceful body can use proteins for energy by converting them to fatty acids or glucose.
Proteins come to us in meat, fish, eggs, beans, nuts, and dairy products. Vegetables have proteinstoo, but are called "incomplete" proteins because they do not contain every amino acid. That is how vegetarian diets can lack important nutrients.
Only 10–15 percent of all calories an average person eats daily should come from protein, which amounts to two or three servings a day. A servingequals two to three ounces of meat, poultry, or fish; an egg; or one-half cup of cooked beans. Because the body cannot store it as protein, it is converted into a stored energy source: fat.
Although athletes may need a little more protein than non-athletes, the protein consumed in the typical American diet exceeds the protein needed. Supplying the body with more than it needs is hard on the kidneys besides being hard on the waistline. Balance is important: if a diet is not balanced and even if calorie intake is too low, the body will use protein for energy rather than for building muscle. This is why carbohydrates are so important.
Sources of vitamins and minerals as well as proteins and carbohydrates, vegetables bring variety to any diet for good health. Along with them, fruit contributes vitamins, minerals, and sugar. Oranges, grapefruit, tomatoes, and strawberries are rich sources of vitamin C, and pumpkin, carrots, apricots, and cantaloupes are good sources of vitamin A. Broccoli is a good source for both. Though vegetables can provide many proteins the body needs, they are considered an incomplete source of protein because they cannot provide all of the amino acids, the building blocks of protein. Of the necessary amino acids, the body can manufacture all but nine, and these, called the essential amino acids, must come from diet. Vegetarians combine incomplete proteins, pairing beans with corn tortillas or beans with rice, for example, to achieve a complete protein. Or they combine an incomplete protein, such as pasta, with a complete one, say a milk product such as cheese.
Fats include many categories. One you′ve heard about is cholesterol, one of the sterols. The major storage form of fats is triglycerides, which consists of glycerol and three fatty acids. One gram of fat yields nine calories. This is the body′s favorite way of storing energy because it is so efficient. To lose one pound of fat, more than twice as many calories as are in one pound of glycogen or protein must be burned.
Fats appear mostly in foods we love: ice cream and chocolate, plus meats, eggs, whole milk, cheese, fried foods, butter, margarine, salad dressings, oils, and mayonnaise, to name a few. Brussels sprouts have no fat.
Diets with high fat intake are associated with being overweight or obese and having heart diseaseand diabetes. Fat intake should not exceed 20–25 percent of total calories. A gram of fat supplies more than twice the calories of a gram of carbohydrate or protein. Not fair, is it?
The Food and Nutrition Board of the National Research Council states that a proper mix of foodsshould provide adequate amounts of vitamins and minerals. Nonetheless, it is probably a wise safety measure to take a multiple vitamin supplement every day.
Now, some people think that if a little is good, a lot will be better, so they take megavitamin doses. These regimens are probably not helpful; in some cases it simply creates very expensive urine, in others it is dangerous.
The key water-soluble vitamins are B complex and C vitamins. Too much niacin from a B-complex vitamin can cause fatigue, tingling, skin flushing, and liver damage. Megadoses of the other water-soluble vitamins do not appear to be toxic because the body simply rids itself of the overload by dumping the excess vitamins into the urine.
Fat-soluble vitamins are a different story. These are vitamins A, D, E, and K, and they remain in your body, especially in your liver, until your body uses them. If more than is needed is consumed, they accumulate and toxic symptoms result. In fact, too much vitamin A can be deadly.
Minerals fall into two categories: major and trace. The human body requires relatively large amounts (more than 100 mg a day) of major minerals,including calcium, iron, magnesium, potassium, and sodium. Of the trace minerals, including chlorine, chromium, copper, fluorine, iodine, manganese, molybdenum, phosphorus, selenium, sulfur, and zinc, little is needed. Generally speaking and excepting calcium, iron, zinc, and potassium, supplements of the minerals aren′t necessary.
Calcium strengthens the bones of which your knees are made and all other bones and teeth as well. It also aids in the clotting of blood, the signaling of nerves, and the contracting of the heart and other muscles. It also protects against osteoporosis. Some studies have found that calcium (1,200–1,500mg/day) helped reduce the risk of colon cancer in patients who had had colon polyps removed. Such polyps are generally recognized as early precursors of cancer.
The general recommendation is for 800 mg for men and women 25 years of age or older, but a National Institutes of Health Consensus Panel used 800 mg as a baseline and recommended higher doses, especially for older adults and women who are pregnant or breast feeding.
Table 3.2 Daily Calcium Requirements by Age Group:
|Group||Calcium Needed (mg/day)|
|Children 1-10 years||800-1,200|
|Young adults 11-24 years||1,200-1,500|
|Young adults 11-24 years||1,200-1,500|
|Adult Women to age 50 years||1000|
|Woman 50 years and older||1,500|
|Woman who are pregnant or lactating||1,200-1,500|
|Adult mem 25-64 years||1,000|
|Mem 65 years and older||1,500|
If you eat enough dairy products (i.e., drink at least three to four glasses of milk a day), you should get enough calcium. There are 300 mg of calcium in a cup of low-fat milk. If you hate milk, consider low-fat yogurt (415 mg/cup), Mozzarella cheese (550 mg/ounce), or calcium-fortified orange juice (300 mg/cup). Otherwise, take a calcium supplement. Some nutritionists recommend taking calcium supplements at night because of better absorption.
Many young Americans are not getting the calcium they need. In a 1999 survey reported by the Centers for Disease Control, only 18 percent of high school–age students reported drinking three or more glasses of milk per day during the seven days preceding the survey. Furthermore, milk consumption fell as age increased in both girls and boys, with lower classmen being significantly more likely to have drunk three or more glasses than were upper classmen.
Menstruating women should eat plenty of iron-containing foods (for example, spinach, flank steak, figs, turkey, baked beans, pork loin) or take an iron supplement, since iron is the absolutely critical part of the hemoglobin in the blood. Hemoglobin carries oxygen; without enough oxygen circulating, you won′t have the energy you need.
Zinc, important in maintaining a healthy immune system, is required in moderate amounts daily. The recommended dietary allowance (RDA) is 15 mg/day for men and 12 mg/day for women 19 years of age and older. Women who are pregnant or breast-feeding require between 15 mg/day and 19 mg/day. According to the National Institutes of Health, six ounces of beef chuck offers 90 percent of the RDA.
Potassium is a salt-like sodium that your body loses when you sweat. Foods rich in potassium include bananas, orange juice, and cereals. Taking a small daily supplement of potassium might be wise.
The human body is 65 percent water, and it just doesn′t work well with less. Fluid lost during exercise must be replaced. In normal activities, most people do not suffer a water deficiency.
In heavy exercise, though, an athlete "burns" sugar and fat for energy. When fuel is burned, heat is generated, just like a wood fire produces warmth. If a body doesn′t get rid of that heat, it can cook to death. That′s what happens when people have heat stroke. Sweating keeps you from getting too hot. The water cools the skin as it evaporates from it. But with every drop, the ability to cool is diminished. Dehydration reduces the body′s ability to dissipate heat and impairs endurance.
Weighing yourself before and after exercising helps indicate how much water the body has yielded to keep cool. Drink two cups for every pound lost.
How Sweat Works
The main way the body gets rid of heat is to sweat. Why does this work? Because it takes a lot of heat to turn water from a liquid to a vapor. (Just think of how long you heat a pot of water before it boils.) Your body cools itself through the vaporization of sweat. Every drop of sweat that evaporates carries heat with it.
Normally, a person in an hour-long aerobic dance class will burn about three hundred calories, and the heat will be carried off by about a pint (two cups) of sweat. People who exercise harder (like competitive athletes) burn more calories and generate more sweat.
To sweat, the body must have water within it. So those who exercise must continually replace water lost during a workout. As little as two percent dehydration will impair the body′s ability to regulate temperature, and at only three percent dehydration, muscles lose endurance ability, according to McArdle, Ketch, and Ketch in Exercise Physiology (Lea & Febiger, 1986).
Complicating water replacement is the movement of blood to the muscles, leaving the digestive system little power. If a lot of water is consumed during exercise, the body may have a difficult time taking advantage of the available pool. A better idea is to load up before a workout, and then to take a few sips every few minutes as needed. It is unlikely that this will mean more trips to the bathroom–this water will be used for sweat, not urine. In addition, making sure the water is cool will further help ensure against overheating.
Special "Exercise" Fluids
But what about sports drinks that replace "lost electrolytes"? Medical reports leave experts divided on the use of these supplemental drinks. They may be useful when someone who is exercising has overextended himself, and his sweat begins to taste salty. A longer or heavier or faster workout may make demands on the body that these drinks can meet, since they provide both sodium and potassium. Supplements with sugar should not be necessary unless the workout extends more than one hour at a stretch.
For athletes engaged in endurance events, experts have recommended adding carbohydrates to fluids to bolster fluid replacement with the carbohydrates, which are meant to sustain the concentration of blood glucose and help ensure carbohydrate oxidation throughout the event. Practical recommendations include monitoring weight loss as an index to water depletion (each pound lost corresponds to about 15 ounces of lost water and replacing it with fluids at about 80 percent the rate of sweating). For endurance events, experts have estimated that both carbohydrate and fluid needs can be met by ingesting 19–38 ounces of fluid per hour containing four percent to eight percent carbohydrate.
This is a section from Dr. Jack E, Jensen’s book The One Stop Knee Shop. Read the next section Diet and Weight Control.