Carbohydrates

Chapter 3

What are carbohydrates (CHO)?

• Molecules– Carbon– Hydrogen– Oxygen

• Formed by plants via photosynthesis

• Stored in plants as starch

Photosynthesis

CHO Classification

• Simple CHOs– Monosaccharides– Disaccharides

• Complex CHOs– Oligosaccharides– Polysaccharides

Photos © Photodisc

Simple Carbohydrates

• Monosaccharides– Glucose– Galactose– Fructose

• Disaccharides– Sucrose– Lactose– Maltose

Complex Carbohydrates

• Oligosaccharides– Short chains– 3 to 10 sugars

• Maltodextrin• Corn syrup

• Polysaccharides– Long chains– > 10 sugars

• Starch• Glycogen

Other Polysaccharides

• Dietary Fiber– Nondigestible– Plant sources– Soluble versus insoluble

• Functional Fiber– Nondigestible– Commercially produced or isolated

form

• Dietary + Functional = Total Fiber

Photo Courtesy of Renee Comet/ National Cancer Institute

Artificial Sweeteners

• Classified as:– Non-nutritive– Nutritive

• Generally sweeter than sucrose

• Must have FDA approval

• Have GRAS status

Artificial Sweeteners (continued)

• Saccharin– Sweet’N Low

• Aspartame– NutraSweet

• Acesulfame-K

• Sucralose– Splenda

• Tagatose

• Sugar alcohols

Functions of CHOs

• Energy source– 4 kcals/gram– Primary energy source for the body, especially

during exercise– Only energy source for high-intensity anaerobic

exercise

• Energy source for the cells of the Central Nervous System (brain)

Functions of CHOs (continued)

• Metabolic primer for fat metabolism:– Provides critical intermediates for energy

production from fat breakdown– In other words, CHO is needed for fat to be

used for energy.– Prevents ketosis

• Prevents protein catabolism in body:– Decreases gluconeogenesis– Spares muscle tissue

Functions of CHOS• Prevents protein catabolism in body:

– Decreases gluconeogenesis– Spares muscle tissue– Referred to as protein-sparing effect of CHO.– As we will learn soon, proteins are needed for

many important functions in the body. If there isn’t enough CHO then the body must divert proteins from these important functions to the function of producing energy. This is not desirable.

CHOs and Health• Phytochemicals

– Found in plants– Antioxidants– Enhance immune function

• Fiber (find a combo of soluble and insoluble in fiber-containing foods)– Soluble

• Lowers cholesterol– Insoluble

• Adds bulk to intestinal contents• Decreases transit time of intestinal contents• Draws water into intestinal contents

CHOs and Health (continued)

• Fiber may be related to:– Reduced risk of heart disease (cholesterol

lowering)– Reduced risk of cancer (phytochemicals,

antioxidants, and decreased intestinal transit time)– Improved weight management (feeling of fullness)

• Simple sugars (refined sugars) may harm health:– Dental caries– Weight gain

Carbohydrate Intake

• Recommendations– 5 to 10 g/kg of body weight– Usually 45% to 65% of total daily calories

• May go as high as 75%– Recommendations will change based on an

athlete’s stage of training and competition schedule

Let’s apply this new information!Molly is a 19-year old collegiate athlete. She and her teammates are training daily

as the cross country season meet opener is one month away. She is 5’8 and weighs 140 pounds. She is consuming approximately 3000 total calories daily and 487 grams of CHO.

1. What percentage of her total calories are derived from CHO?

2. How does this compare to the recommendation?

3. How many grams of CHO per kilogram of body weight is Molly consuming?

4. How does this compare to the recommendation?

5. Overall how would you assess Molly’s CHO intake?

Here’s how to apply the info:1. What percentage of her total calories are derived from CHO?

Total calories = 3000

Calories from CHO = 487 grams of CHO x 4 calories/gram of CHO = 1958 calories

[1958 calories / 3000 calories] x 100 = 65%

2. How does this compare to the recommendation?

The recommendation is that 45% to 65% of total calories are from CHO. Molly is within the recommendation.

3. How many grams of CHO per kilogram of body weight is Molly consuming?

Weight = 140 pounds divided by 2.2 pounds/kilogram = 64 kilograms

487 grams CHO / 64 kilograms body weight = 7.6 grams CHO / kg body weight.

4. How does this compare to the recommendation?

The recommendation is to consume 5 to 10 g CHO per kilogram of body weight. Molly is within the recommendation.

5. Overall how would you assess Molly’s CHO intake?

Her intake falls within the recommendations and thus appears adequate for pre-season training.

Carbohydrate Sources

• Whole grains• Vegetables and fruits

– Pros and cons of various forms

• Dairy and dairy alternative products

• Beans, lentils, nuts, seeds, and soy products

• Sweets Photo © PhotoDisc

Glycemic Index Versus Glycemic Load

Glycemic Index (GI)• Glycemic effect of an

isolated food• Based on elevation of

blood sugar levels two hours after ingestion

Glycemic Load (GL)• Glycemic effect of the

diet • (GI x CHO content per

serving) ÷ 100

How useful are GI and GL in sport?Both are quite controversial in the literature. I’d like for you to be familiar with the terms but we will not spend time discussing what they are and how to apply them.

Carbohydrate Metabolism

Importance of CHO in Exercise

• Serves as an energy source both at rest and during exercise.

• Becomes sole source of energy during very intense exercise.

• However, stores of CHOs in body are limited.

Importance of CHO in Exercise

• Blood glucose levels and the amount of CHO (i.e., glycogen) stored in the muscles can delay fatigue.

What should an athlete eat in the days leading up to competition?

• Well-balanced diet in which 55% to 70% of total calories come from CHOs

• Carbohydrate loading?

Photo © Digital Stock

What should an athlete eat in the hours leading up to competition? (continued)

• 4 to 24 hours prior to competition– Balanced high-CHO

meals/snacks

– Familiar foods

– CHO = ~ 60% to 70% of total calories

Photo © Photodisc

What should an athlete eat in the hours leading up to competition? (continued)

• 0 to 4 hours prior to competition– 1 to 4.5 grams CHO/kg

body weight– Easily digested, low fiber– Complex carbohydrates– Low glycemic index– Experiment in training

Photo © Able Stock

What about CHO consumption during competition?

• Types of CHOs– Glucose, glucose

polymers, fructose, starches

– Sport nutrition products• Gels• Bars• Drinks

Photo © Photodisc

What about CHO consumption during competition? (continued)

• Amount of CHO– 60–70 grams per hour– Individual tolerance

will vary greatly!

• Timing of intake– Begin soon after

onset– Continue at regular

intervals Photo © ComstockImages/AlamyImages

What should an athlete eat after competition?

• CHO consumption after exercise is important for glycogen replenishment.

• CHO should be consumed as soon as possible after exercise.

• Solid or liquid forms are acceptable.

• High glycemic index sources are preferred.

How much should an athlete eat after competition? (continued)

• 1.2 g of CHO/kg– Immediately after– Every hour for 3–4

hours

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