Carbohydrates for Sports Performance

Because nutrition in general plays such a large part of performance and an everyday healthy life, I decided to throw in a sports nutrition article. This may turn into a 3 part series if I get around to the other 2 macronutrients. It feels that for the past couple of years carbohydrates have gotten a poor rap either because of Netflix, Fad Diets and/or Instagram Influencers. One thing that is important to understand is that carbohydrates are not evil, but instead are the primary source for energy. I want to talk about carbohydrates and how they affect performance, but before I dive into the specifics it's vital to understand what the crap carbohydrates are and what exactly occurs during the consumption and digestion process of them. 

I will spare the boring organic portion and simply say that there are two classifications of carbohydrates, simple and complex. Simple carbohydrates are composed of no more than 2 sugar molecules linked together and complex carbohydrates are made up of longer (3 or more) chains of sugar molecules. 

Simple carbohydrates include two types, monosaccharides (simple sugars) and disaccharides. One can guess from the name that monosaccharides only include 1 molecule of sugar. The most common monosaccharides are glucose, fructose and galactose. Rarely will anyone consume these alone, as they are commonly combined with other sugar molecules to create disaccharides. Glucose is considered the most important carbohydrate for cell energy and brain function, while fructose is responsible for the sweet taste in fruits and vegetables. As you will read, glucose is the key to almost everything, so I will talk more about glucose later on. Disaccharides (2 monosaccharides combined) may be more familiar to some, with sucrose (table sugar), lactose and maltose being the most common types. 

There are two types of complex carbohydrates, oligosaccharides and polysaccharides. This is also an important time to mention that the complex carbohydrate glycogen is the storage form of carbohydrate in the body. Glycogen is basically a long chain of glucose molecules that the body stores in certain places. Oligosaccharides include high fructose corn syrup, corn syrup and maltodextrin. Polysaccharides are the longest chained sugars of any carbohydrate, and they include starches and fiber. Examples of foods with a large amount of starch are breads, beans, pasta and some cereals - to name a few. Fiber is found in all plant based foods, with there being two types but I won’t get into that for the sake of this article. Fun fact, fiber is indigestible by the body so basically it's noncaloric! YAY! 

Now that we have briefly gone over what carbohydrates are..

Let's go over what exactly happens to carbohydrates when consumed by an individual. Let's take a piece of bread for example. When a piece of bread is put into the mouth, salivary amylase (an enzyme) will start to break down the starch into individual molecules of glucose-simple sugars. There is not a whole lot of breakdown in the mouth, but enough to get the digestion process started. Once in the stomach, stomach acid with the help of hydrochloric acid will destroy the salivary amylase stopping that process (Fink & Mikesky, 2018). The stomach will then use smooth muscle to swirl the stomach acid with the bread to prepare it for the move to the small intestine. 

Once in the small intestine, pancreatic amylase (an enzyme) will break down the starch into the disaccharides maltose, while brush border disaccharidases (an enzyme) will break down the disaccharides into certain monosaccharides (Fink & Mikesky, 2018). There are certain enzymes for certain disaccharides for example, lactase breaks down lactose into the monosaccharides galactose and glucose. 

Now broken down into simple sugars (glucose) in the small intestine, the absorption process is ready to begin. Most of the absorption process occurs within the small intestine and no absorption occurs in the large intestine. Absorption happens via facilitated diffusion or active transport, but I won’t get into that, instead I will say that once the sugar molecules cross the intestinal membrane of the small intestine they will enter the bloodstream. 

After glucose is absorbed from the small intestine it can either do a couple things:

1. Enter the bloodstream

2. Be used as ATP (energy) in skeletal muscle

3. Stored as glycogen (stored carbohydrate) in skeletal muscle

4. Used as ATP within the liver 

5. Stored as glycogen in the liver

6. Be converted into triglycerides and stored in fat tissue

To sum it all up, carbohydrates are a form of energy that are either used for immediate energy, stored for a time when energy will be needed or simply stored in fat tissue (if you eat too much). 

Alright, let’s cut to the chase. Carbohydrates are the ultimate energy source, especially for moderate to high intensity exercise. Actually, carbohydrates are the only macronutrient (protein, fat, carbs) that can be used for high anaerobic exercise due to the fact that they metabolize so quickly. They can also be broken down and used for aerobic activity. Carbohydrates also fuel the energy for nerves in the nervous system (Fink & Mikesky, 2018). Because of the important role carbohydrates play in performance it is detrimental to decrease the amount that is consumed by an athlete. If an athlete consumes a low level of carbohydrates the body, inreturn will break down protein in the muscle to keep up with the needed energy demands. 

As mentioned above, carbohydrates are more efficient in producing energy than any other macronutrient. However, during low intensity exercise fat is the main energy source with the help of carbohydrates, but there is a “crossover” point as exercise intensity increases the shift to carbohydrates becomes greater. Just like athletes should condition based on the demands of their sport they should fuel their body the same way. I talk a little bit on this in If you're an Athlete, Think Twice Before Doing any Distance Running. This is our body’s way of utilizing the small amount of oxygen available, but still delivering as much energy as possible. For example, in soccer there are bouts of repeated sprints and the only macronutrient that can supply energy for such activity are carbohydrates. This is because carbohydrates are the only macronutrient that can metabolize fast enough due to the metabolic pathway of glycolysis, but the downfall? There is a build-up of lactic acid.

The great part about carbohydrates is they can be stored in skeletal muscle, unlike fat. Why is that great? Once energy is required, there is no delay process because carbohydrates are already there, ready! Think about it like this, you know how there are those annoying people at the airport that stand around the gate waiting for their number to be called so they can board first? Well, once their number gets called they end up getting on the plane before those waiting patiently in a chair. This happens because they are already present, ready to take on anyone in their way. To make it clear I am not saying everyone should swarm the gate because those people are annoying, but hey they do get on the plane quicker. It was the only analogy I could think of. 

Carbohydrates can also be broken down and used for energy without or with minimal oxygen available. In order for fats and proteins to be used for energy, an athlete's muscle will need to have enough oxygen available, which is not always going to happen due to the high intensity demands of sports.

So how much carbohydrates should an athlete consume? This depends on many factors, but the general recommended amount is 3-12 grams of carbohydrates per kilogram of body weight a day. Those athletes who are on the endurance end of sports are recommended to be within the 8-12 g/kg body weight (Fink & Mikesky, 2018). 

An athlete needs to stay on top of their carbohydrate intake to make sure that they don’t run out of energy and in return hinder their performance. By staying within the recommended carbohydrate intake given, the body will be able to store enough glycogen in the liver and muscle. By having stored glycogen there will be immediate available energy within the muscle when needed. At the same time, having an increased level of glycogen will decrease the time for that athlete to become fatigued. This is why many athletes will “carb load” before a game or event. Carbohydrate loading “top offs” athletes glycogen levels so they can maintain proper intensity throughout the game or race all while delaying the onset of fatigue.

Interestingly enough, research has shown that muscle glycogen stores are higher in type II than type I muscle fibers and resistance training can also increase muscle glycogen stores (Wildenman et al., 2010). Want to help increase muscle glycogen levels? Train fast! Music to my ears.

What kinds of carbohydrates should an athlete consume? Carbohydrates that are rich in fiber and nutrient dense. Complex carbohydrates such as whole wheat breads, brown rice, oatmeal, quinoa and whole wheat pasta are great sources. An athlete should limit refined and white carbohydrates. 

It has been recommended that some athletes should consume carbohydrates before exercise, during exercise and after exercise (Wildman et al., 2010). Doing so can help aid sports performance and recovery. This is just the tip of the iceberg when it comes to carbohydrates and their ability to enhance performance. Carbohydrates are not evil, but instead are essential for an athlete to perform at a high level. It’s important for athletes, parents and coaches to understand that cutting an athletes carbohydrates can have a detrimental effect on performance. 

References

Fink, H., & Mikesky, A. (2018). Practical applications in sports nutrition (5th ed).  Burlington, MA: Jones & Bartlett Learning.

Wildman, R., Kerksick, C., & Campbell, B. (2010). Carbohydrates, Physical Training, and Sport Performance. Strength and Conditioning Journal,32, 21-29.