Despite a recent glut of alternative nutrition plans in the past 10 years that force carbohydrates out of diets, they are still the preferred energy source for all activities. There are three macronutrients: carbohydrates, protein and fat. The research has been published and the scientists have concluded: Without carbohydrates, performance will decrease.
Early researchers discovered when the body runs out of carbohydrate (CHO) stores and relies on mostly fat for energy, physical performance declines dramatically. Long distance athletes call this “hitting the wall” or “bonking.”
Carbohydrates are stored as glycogen in skeletal muscle and the liver. Because these stores are continuously used throughout the day, they need to be continuously replaced by food. The type of food, or CHO sources, eaten affects how efficiently the body processes it. There are two types of carbohydrates: simple and complex. Here, you'll learn a little about each and how they affect the body of an athlete.
Mmm... Cake... Candy... Coca-Cola...Balance bars? Yep, and the others like them. Simple carbohydrates are primarily composed of sugars, and are usually associated with sweet-tasting foods. They exist as glucose and fructose, but are found more on nutrition labels as high-fructose corn syrup, sucrose, brown sugar, confectioners’ sugar, invert sugar, raw sugar, dextrose and turbinado.
Most glucose is absorbed quickly through the small intestine, but some is absorbed in the stomach, which causes rapid fluctuations in blood-sugar level. This rapid rise in blood sugar can be measured, and it is referred to as the glycemic index. These fluctuations can increase appetite and cause more sugar cravings (which is why it's hard to cut yourself off after just a handful of Skittles).
Fructose is absorbed more slowly, and does not cause the rapid rise in blood-sugar level, thus it has a low glycemic index value. However, it has a greater tendency than glucose to convert into fat.
Basically, when liver glycogen stores are full, excess fructose will likely be converted into fat. Glucose, on the other hand, is metabolized in our muscles and used as energy, however it can also be converted into fat, but less likely unless muscle glycogen is full and there is no need for glucose at the time.
But a small amount of fructose does have its place in an athlete’s diet because it is primarily metabolized in the liver, restoring liver glycogen. The brain derives most of its energy from the liver. Any kind of mental fatigue or low blood sugar, called hypoglycemia, can have a negative effect on sport judgment and performance.
Except for fruit (which contains fructose), most of these foods provide empty calories, or calories that supply no vitamins and minerals. Read labels to be aware of inferior nutrition bars that use high-fructose corn syrup, sucrose, or sugar as one of the first three ingredients in their “energy” or “protein bar”, such as PromaxTM, BalanceTM bars, or ZoneTM bars. These rely more on taste than actually improving your health in order to sell them. Do not completely deprive yourself, but try to limit simple carbohydrates in your diet.
Mom was right about the vegetables and potatoes – keep eating them. These are large chains of sugar units (called polysaccharides) arranged to form starches and fiber.
Complex carbohydrates are plant based and they include vegetables, whole fruits, rice, pasta, potatoes, grains (brown rice, oats, wheat, barley, corn), and legumes (chick peas, black-eyed peas, lentils, as well as beans such as lima, kidney, pinto, soy, and black beans).
Processed forms of polysaccharides are maltodextrin and glucose polymers, which are shorter chains of glucose than starch and are commonly used in sport drinks because they are more soluble in water than starch is. You can find maltodextrin in most energy bars, protein bars or meal-replacement shakes. This is a nice alternative when on the run, preparing or recovering from a competition/workout and/or away from any whole food choices.
When starch is eaten, unlike glucose, it is digested slowly, releasing glucose molecules from the intestines into the bloodstream at a slow, steady rate. This slow release provides both a prolonged supply of glucose to the bloodstream and a supply of energy that spares and replenishes muscle glycogen.
Carbohydrates and Muscle Preservation
What is often lost in the carb-bashing literature are the protein and muscle sparing benefits of carbohydrates. Protein can be converted into energy by a process called gluconeogenesis. Unless sufficient dietary protein and carbohydrates are ingested, your body will resort to getting the glycogen building blocks from your own muscle, a source of protein. As a result, athletes lose muscle, become weaker and have to work hard to regain the lost muscle. This muscle loss happens especially to people on a low-carbohydrate diet without an exercise program. But if adequate carbohydrates are available, muscle won't be used as an energy source.
During the 1980’s, the diet-rage was low-fat, high-carbohydrate. During the 1990’s, the rage was low-carbohydrate, high-fat. Today, the latest and greatest “discovery” is the glycemic index (GI). As discussed above, the GI is a measurement of the way the blood sugar responds two hours after an equivalent amount of pure glucose is ingested. Foods that are digested quickly and soon appear in the bloodstream have a high GI and raise blood sugar and insulin concentrations quickly. Foods that are digested slowly have a low GI. By eating foods with a stable GI, blood sugar and insulin concentrations are more stable, which should reduce appetite and help mood.
The type of CHO is not correlated with the GI. For example, a complex CHO such as white potatoes has a high GI, while, as mentioned above, fructose has a low GI. The rate that a food is digested is the only determinant of its GI and metabolic effect. Foods are labeled as being high (GI>85), moderate (GI=60-85), or low (GI<60).
With this in mind, we can use the GI of a food to determine when we should eat it. Foods that have a low-GI should be eaten throughout the day to maintain blood sugar levels and ensure a sustained amount of energy. High-GI foods should be eaten during workouts, sometimes pre-workouts and definitely post-workouts and competitions in order to help spare muscle glycogen (i.e. pre-exercise) and replenish muscle glycogen (i.e. during and post-exercise).
Understand that the overall GI of a meal is affected by several factors. These are the type of sugar, the amount of fiber, protein and fat, portion size, and the preparation method of the food.
Research and Low-Glycemic Index Foods
Currently, there are no sufficient long-term studies with large subject groups, but we do have some short-term research.
The data suggests that low-GI diets:
- Improved blood profiles versus high-GI diets
- Increase insulin sensitivity in diabetics
- Promote a “full” feeling
- Decrease blood pressure and cardiovascular disease risk
- Decrease breast, various digestive and reproductive cancer risks
- May improve weight loss when calories are restricted versus a high-GI diet
The GI is still a controversial issue. Others argue that we usually eat a combination of macronutrients during a meal. Thus, the glycemic effects of a mixed meal may be quite different than when a food is tested alone in a fasted state. However, the GI does show that carbohydrates do behave differently on blood glucose and hormonally.
Hopefully you now have a better understanding of how and why you should incorporate certain carbohydrates into your diet as an athlete.
Read nutritional labels and become familiar with what type of CHO you are eating when you are eating it.
Focus on preparing low-GI foods throughout the day, and make sure to have your high-GI foods available post-workout. It is a horrible feeling of knowing that you have the ability to out-perform your opponent, but you just do not have the energy to do it. You do not want your lack of nutritional preparation to prevent you from succeeding. Eat well. Live well.