A Closer Look at "Types" of Carbohydrate

A few weeks ago, after writing about carbohydrates, a follower of mine on Twitter asked a question. He was interested in knowing whether simple carbohydrates should be consumed between close spaced workouts and complex carbohydrates during longer rests?

To answer this question we are going to have to take a closer look at the types of carbohydrates.

As I previously discussed, carbohydrates can be classified as simple or complex or as sugars and starches. But, they can also be classified as “quick” or “slow” in a system, I am sure many of you have heard before, the glycemic index (GI). The textbook, Practical Applications in Sports Nutrition (2 nd ed.), defines the glycemic index as “an index for classifying carbohydrate foods based on how quickly they are digested and absorbed into the bloodstream. The more quickly blood glucose rises after ingestion, the higher the glycemic index” (p. 78). Nancy Clark’s Sports Nutrition Guidebook defines the glycemic index as, “how 50 grams (200 calories) of carbohydrate (not counting fiber) in a food will affect blood sugar levels” (p. 107). To give you an example, if you were to consume a high GI food, such as white bread, it could cause a quick rise of your blood sugar, whereas, if you were to consume a low GI food, such as kidney beans, it would cause a slower increase of your blood sugar.

Many people often associate simple carbohydrates with high GI foods and complex carbohydrates with low GI foods, perhaps this is what my Twitter follower thought? (Perhaps not and I apologize if I am wrong Twitter follower ☺)
However, there are quite a few foods that do not fit this assumption. Complex foods can have a high GI and believe it or not, simple carbohydrates can have a low GI. For example, fructose, a simple carbohydrate has a low GI. And a baked potato, a complex carbohydrate has a high GI.

SO, why does any of this matter or does it not matter at all??

Originally, the glycemic index was designed and intended for people with diabetes, as a means of helping them control their blood sugar levels. The glycemic index examines foods as single food items, not combination foods, such as lasagna. Of course scientists started to become interested in the glycemic index and its potential in aiding athletic performance. There have been quite a few research studies performed. However, results are mixed and the Sports Nutrition A Practice guide for Professionals (4th ed.) states, “additional studies are warranted” (p.18).

There are pros and cons to the glycemic index. The glycemic index can be affected by many factors. And so, I personally believe there are many limitations to the GI and athletes shouldn’t get all worked up about the glycemic index.

The following are factors/limitations that can affect the GI of a food (1):
• Fiber content of a food
• Protein and Fat content of a food (can delay a rapid increase in blood glucose levels)
• Liquid versus solid form
• Timing of the meal
• Consuming a variety of foods at one time (meal) (Remember: the GI only examines a single food item, not combinations)
• Consuming more than one carbohydrate food at a time

ALSO…

“Each of us has a differing daily glycemic response that can vary approximately 43 percent on any given day” (2). AND, remember well-trained athletes’ muscles quickly use carbohydrate in the bloodstream, meaning that athletes produce LESS insulin and therefore, do not have increases in blood sugar levels, like unfit people can have (2).

Based on these limitations of the glycemic index and through my own experience, the best advice I can offer is to consume foods high in carbohydrate (they are a main source of FUEL for an athlete) that digest well, taste good, and that work best for YOU! I always tell my athletes, just as you practice for your sport, you have to practice eating for your sport! Try different types of carbohydrate before, during and after your workouts to know which ones work well for you. What works well for you, may not work well for your friends or teammates! You want to make sure that they digest well and don’t cause gastric distress. Keep in mind, the time to try a new food or drink should be around times of practice, NOT competition, you don’t want to try something new on the day of a race!

However, if you want to know what some of the research says and try it out for yourself, here is what some research recommends (Remember…more research is needed and there are NO set recommendations for athletes regarding GI)

1.) Pre-exercise meal: Low GI carbohydrate foods (theorized to provide sustained energy) (1, 3)

2.) During exercise: Moderate to High GI carbohydrate foods (For high-intensity or long endurance sports, there is a need for carbohydrate, especially if glycogen stores are low or depleted. These foods can quickly supply glucose for energy) Example: Sports Drinks. (1, 3)

3.) Post-exercise meal: Moderate to High GI carbohydrate foods (As mentioned above, these foods can quickly supply glucose for energy, but they can also replenish glycogen stores quickly) (1, 2, 3).



Going back to my Twitter followers’ question… “Should simple carbohydrates be consumed between close spaced workouts and complex carbohydrates during longer rests?”

From the glycemic index perspective and research, High GI carbohydrate foods should be consumed between close spaced workouts, again, because they provide glucose quickly and can restore glycogen quicker than low GI foods. Again, you want to consume foods that are easily digested between workouts! FYI… carbohydrates digest quicker than protein and fat! You also want to make sure you are consuming enough carbohydrate between workouts as well. The last thing you want is not having enough energy! I will talk about this topic more when I discuss pre- and post-exercise meals. But, a general guideline to follow for post-exercise carbohydrate intake is the following:

1- 1.5 grams of carbohydrate/ kilogram of body weight immediately after exercise (2, 3)
Additional 1- 1.5 g of carbohydrate/ kg 2 hours later (3)

As for carbohydrate intake during longer rests (such as 24-hours), there is some research that supports a Low GI diet. This information relates back to information from my “carbohydrate rebuttal.” For example, “the low-GI diet might facilitate better replacement of intramuscular fat stores (important for endurance) as well as enhance the use of fat for fuel, instead of the limited (and limiting) glycogen stores” (2).

In summary, carbohydrates are very important for energy and should therefore be consumed in an athletes diet everyday. How you choose what “types” of carbohydrates to consume is up to you. However, they should be easy to digest and work best for you. I can’t emphasize enough how important it is to consume carbohydrates after workout or between workouts, as well as during workouts lasting longer than 90 minutes! All types of carbohydrates are important, especially fruits, vegetables and whole grains, as all of these provide specific vitamins, minerals, fiber, and phytochemicals. If you decide to try and follow the GI index and the proposed recommendations for athletes, go for it, BUT keep in mind the limitations of the GI, the various factors that can affect the GI of foods, and that it is not easy to follow the GI.


If you are interested in more information about the glycemic index or want to check out an index of various food GI go to this website:
Home of the Glycemic Index
http://www.glycemicindex.com/

REFERENCES:

1. Hedrick Fink, H., Burgoon, L. A., & Mikesky, A. E. (2009). Practical applications in sports nutrition (2nd ed.). Sudbury, MA: Jones and Bartlett Publishers.

2. Clark, N. (2008). Nancy clark’s sports nutrition guidebook (4th ed.). Champaign, IL: Human Kinetics.

3. Dunford, M (Ed.). (2006). Sports nutrition a practice manual for professionals (4th ed.). Chicago, IL: American Dietetic Association.

My Carbohydrate Rebuttal

This is my response to a comment from a reader about my carbohydrate blog entry...

Thank you for reading and commenting on my blog, I truly appreciate it!

I agree with you that a high carbohydrate diet is not for everyone. Perhaps, I came off that way, but in my personal opinion a BALANCE of ALL macronutrients; carbohydrate, protein and fat, as well as total calorie intake are extremely important for athletes. Fat and protein should not be omitted from an athletes diet! Nor should carbohydrate!

YES, there has been some recent research studies examining high-fat diets and ENDURANCE athletes. The results of many of these studies have been intriguing and interesting.

Any information that I post on my blog, I want it to be scientific and evidence-based. I often turn to the American Dietetic Association (ADA) for scientific, evidence-based information. And so...

The 2009 Position of the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance states the following:

"Approximately 50% to 60% of energy during 1 to 4 hours of continuous exercise at 70% of maximal oxygen capacity is derived from carbohydrates and the rest from free fatty acid oxidation (3). A greater proportion of energy comes from oxidation of free fatty acids, primarily those from muscle triglycerides as intensity of the exercise decreases (3). Training does not alter the total amount of energy expended but rather the proportion of energy derived from carbohydrates and fat (3). As a result of aerobic training, the energy derived from fat increases and from carbohydrate decreases. A trained individual uses a greater percentage of fat than an untrained person does at the same workload (2). Long-chain fatty acids derived from stored muscle triglycerides are the preferred fuel for aerobic exercise for individuals involved in mild- to moderate-intensity exercise (4)."

So, yes, a "trained" endurance athlete can use energy derived from fat sources, sparing energy from glycogen stores. Again, it is amazing how our bodies can adapt. I did know that endurance athletes use carbohydrate and fat as a fuel source, I don't know if I mentioned it in this entry, but I may have in the protein entry, because a small amount of protein is also used for energy for endurance athletes.

Yet, the ADA, Dietitians of Canada, and the ACSM go on in this position paper to recommend the following:

"The Acceptable Macronutirent Distribution Range for fat is 20% to 35% of energy intake (17). The 2005 Dietary Guidelines (16) and Eating Well with Canada's Food Guide (28) make recommendations that the proportion of energy from fatty acids be 19% saturated, 10% polyunsaturated, and 10% monounsaturated and include sources of essential fatty acids. ATHLETES should follow these general recommendations."

"Consuming < or equal to 20% of energy from fat does NOT benefit performance. Fat, which is a source of energy, fat- soluble vitamins, and essential fatty acids, is important in the diets of athletes. High-fat diets are not recommended for athletes."

"Carbohydrate recommendation for athletes range from 6 to 10g/kg body weight per day. Carbohydrates maintain blood glucose levels during exercise and replace muscle glycogen. The amount required depends upon the athlete's total daily energy expenditure, type of sport, sex, and environmental conditions."

The protein recommendations are similar to the ones I mention in my protein blog entry.

In my personal opinion and based on the position of the ADA, Dietitians of Canada, and the ACSM, I feel that more research needs to be conducted before recommending a high-fat diet. I think that fat is essential and important for an athletes' diet, as well as carbohydrate and protein. I don't think that any athlete should follow a non-fat or low-fat diet.

If you want to extract information out of running books, Runner's World, "The Runner's Body" (2009) by Ross Tucker, PhD, and Jonathan Dugas, PhD, also discuss fuel sources, both carbohydrate and fat. These authors also discuss how the well trained long-distance runner can adapt to use more fat as a source of fuel, sparing glycogen stores. They state, "the scientific research on high-fat diets and fat-loading is still equivocal." They go on to explain how some research has "found that fat-loading actually improved performance during endurance exercise (p. 144)." They also explain how there is evidence of individual variation, meaning a high-fat diet may help some athletes, but may impair other athletes' performances. They conclude, "given our lack of understanding of the interindividual responses to high levels of fat intake, the prudent approach, for now is to focus on a high carbohydrate diet and make sure that you are not compromising performance by depleting your glycogen stores before exercise... for the average runner engaging in marathons and shorter races, adapting to a high-fat diet is unlikely to yield significant benefits (p.144-145)."

Finally, as to the reasons I explained in my carbohydrate blog entry, carbohydrates are important to athletes as a source of energy, as are fats and protein! No athlete should follow a fat-free or low-fat diet!

Clearing up Carbohydrate Confusion

In recent years there has been a lot of hype in the media about low carbohydrate diets, such as the Atkins diet, as well as negative messages about carbohydrates. It is no wonder that many people are very confused about carbohydrates. Before we begin, what do you think about carbohydrates? What do you know about carbohydrates? Do you know what foods contain carbohydrates?

Similar to the protein entry, I would like to clear up any carbohydrate confusion, dispel myths, and have you thinking positively about carbohydrates by the time we are done.

If you read my entry about protein, you should at least know that carbohydrates are very important for athletes! This is because carbohydrates are the MAIN source of FUEL for your muscles! Especially if you take part in any anaerobic, high intensity sport or exercise (ex. sprinting), as well as endurance exercise (>60 minutes), these types of activity rely primarily on carbohydrates for energy. Whereas, low intensity exercise, such as walking, uses fat for energy.

Carbohydrate 101… again, like protein, we need to learn some basic information about carbohydrates to understand how and why carbohydrates are important for athletes.

What are carbohydrates??

Sure you are probably thinking of examples of food sources such as, bread, cereal, pasta and sugar, but let’s get specific because not all carbohydrates are the same. In the chemistry world, carbohydrates contain a “carbon backbone with attached oxygen and hydrogen molecules” (1). You are probably thinking, “I don’t care, borrrrring!” But this gives you a bit of a clue as to why carbohydrates are named carbo- (carbon) hydrates (H20)! Anyway, carbohydrates can be broken down into 2 groups or families, which are simple and complex. I’m sure you have heard carbohydrates called one of these two groups. But, do you know what they mean? Like its’ name, simple carbohydrates are simple in their structure. Meaning they only have 1 or 2 sugar molecules. In the nutrition world, they are called monosaccharides and disaccharides (mono= 1, di= 2, saccharide= sugar) (1, 2). Examples of monosaccharides include, glucose, fructose, and galactose and examples of disaccharides are, sucrose (table sugar), lactose (milk sugar), and maltose (1, 2). Disaccharides have 2 monosaccharides attached, for example sucrose is a combination of both glucose and fructose. Like the analogy I gave to amino acids, think of monosaccharides as single pieces of Lego. If you connect two or more of these simple carbohydrates together you get a complex carbohydrate. Examples of complex carbohydrates are starches (grains, legumes, potatoes) and fiber. Whether you consume a simple or complex carbohydrate, it eventually gets broken down into exclusively glucose. Even if it’s a mono or disaccharide, it breaks down into glucose (2). Glucose is extremely important because it travels through the blood as blood glucose and provides energy to cells (1, 2). Have you ever participated in a fast or skipped a meal? Were you able to think clearly? Probably not too well and that’s because the brain relies exclusively on glucose for energy!

How does the body use carbohydrate for fuel?

After eating a carbohydrate rich food, your body breaks it down into the simplest molecule, glucose (monosaccharide). Glucose is then used for immediate energy (blood glucose) and the extra glucose gets stored away as GLYCOGEN. Remember… a molecule of glucose is like a single Lego piece and so, if you connect multiple pieces of glucose you make glycogen. Therefore, glycogen can be classified as a complex carbohydrate, since its’ structure is similar to that of starches and fiber. Glycogen is stored in your muscles and liver and is easily available to be used for energy during exercise (1, 2). You may be wondering, how large are these glycogen stores in the muscle and liver? They are not very large stores and can be easily depleted after an intense workout. This is why it is important to consume foods high in carbohydrate everyday in order to ensure sufficient energy for daily practices and competition (3). The amount of stored glycogen varies person to person, but muscles contain the largest amount of glycogen (about 300-400g or 1200-1600 kcal), then the liver (about 75-100g or 300-400 kcal) and finally blood glucose (25g or 100 kcal) (3). Did you know that a well-trained muscle can store much more glycogen than an untrained muscle (2, 3)?! It’s true! Elite endurance athletes’ glycogen stores will be much greater than occasional exercisers’ glycogen stores. Pretty cool how our bodies can adapt, isn’t it?!

Hitting the Wall…

Remember in my entry about the importance of nutrition, when I mentioned distance runners “hitting the wall?’ Well, it relates to muscle glycogen stores and endurance athletes. It occurs when athletes’ muscle glycogen stores become depleted (depending on intensity of activity, usually after 60-90 minutes), the athlete begins to feel tired, fatigued, and the brain tells the athlete to stop (2). Remember the term “bonking?” This relates to liver glycogen stores. Liver glycogen stores are responsible for maintaining blood glucose levels, which, remember, the brain uses glucose exclusively for energy (2, 3). Picture this, an athlete is racing in the morning and they choose to skip breakfast or eating anything before their race (their liver glycogen stores are low, especially after a night of sleeping). How do you think this athlete will feel? Chances are they will feel light-headed, weak, and unable to think clearly. There are ways to overcome these situations, such as eating adequate carbohydrate before exercise, during exercise, and replacing what’s been lost after exercise.

Demands of Daily Training…

If an athlete trains hard everyday and consumes a low carbohydrate diet daily, this athlete will feel constantly fatigued, particularly by the end of the week. There is scientific evidence that if an athlete consumes a diet low in carbohydrate for consecutive days (ex. 3 days or more) this athletes’ muscle glycogen levels will become increasingly depleted each day (2, 3). Again, this is why it is extremely important that athletes consume a diet rich in carbohydrates daily and consume carbohydrate after a workout!

How much carbohydrate should I be consuming??

Recommended DAILY Carbohydrate Intake:

• In general for athletes carbohydrate recommendation ranges from 6- 10 grams/kilogram/day OR 55-65% of your daily calories should come from carbohydrates
• General training needs- 5- 7 grams/kg/day
• Endurance athletes (>60minutes)- 7- 10 grams/kg/day
• Ultra endurance athletes- >11 grams/kg/day

Recommendations taken from Dunford, M (Ed.). (2006). Sports nutrition a practice manual for professionals (4^th ed.). Chicago, IL: American Dietetic Association.

Let’s do an EXAMPLE to help you understand, I will use myself…

I am an endurance athlete (7-10g/kg/day); I weigh 125 lb (125 lb/ 2.2lb/kg = 57 kg)

7-10g/kg/day X 57 kg = 399-570 grams of Carbohydrate per day

How many calories is that??

1 gram of carbohydrate = 4 kcal

399-570 grams X 4 kcal/g = 1596-2280 kcal of carbohydrate

I would consume the lower end of this range, 400g of carbohydrate, since my overall calorie needs are not very high and my mileage is not very high either.

FYI

1 gram of carbohydrate = 4 kcal

1 gram of protein = 4 kcal

1 gram of fat = 9 kcal

1 gram of alcohol = 7 kcal

*I will go over carbohydrate recommendations before, during, and after exercise, as well as carbohydrate loading in another entry*

SOURCES of Carbohydrate-

Fruits, Vegetables, Grains (rice), Pasta, Starches (potatoes), Legumes (beans) Breads, Cereals, Dairy Products.

In SUMMARY…

Whether you participate in intense sports, such as basketball, football, hockey, soccer, or compete in endurance sports, such as cycling, running, or swimming, carbohydrate is a primary source for fueling your body! Consuming a diet low in carbohydrate can impair your athletic performance, and who wants that? As you have learned about glycogen storage, hopefully you understand why it is important to consume a diet high in carbohydrate daily, as well as the importance to consuming carbohydrates before, during and after exercise!

For more information, check out:

“Do high carbohydrate diets improve exercise performance?”

http://www.gssiweb.com/Article_Detail.aspx?articleid=900

REFERENCES

1. Hedrick Fink, H., Burgoon, L. A., & Mikesky, A. E. (2009). Practical applications in sports nutrition (2^nd ed.). Sudbury, MA: Jones and Bartlett Publishers.

2. Clark, N. (2008). Nancy clark’s sports nutrition guidebook (4^th ed.). Champaign, IL: Human Kinetics.

3. Dunford, M (Ed.). (2006). Sports nutrition a practice manual for professionals (4^th ed.). Chicago, IL: American Dietetic Association.