Carbohydrates- A Runner’s Best Friend.

Why are Carbohydrates so Important?

Carbohydrates are the most important fuel for exercising muscles and for an optimally functioning brain- which is critical for navigating difficult trails and overcoming challenging situations that may arise during a running event. 

Role of Carbohydrates in Exercise

• Preferred energy source for the body- especially, during high intensity/ anaerobic exercise (fatty acids and proteins cannot get used in anaerobic metabolism)  

• Primary fuel for working muscles (as muscle glycogen) 

• Primary and preferred fuel for the brain- you need to be able to use your brain optimally during mentally challenging endurance events

• Necessary for the function of certain tissues that cannot use other substrate for energy (blood cells, kidneys, etc)

• Spares proteins/ lean muscle mass from getting broken down and used for energy

• Carbohydrate containing foods provide essential nutrients, such as B vitamins and vitamin C

• Carbohydrates, as simple sugars, are rapidly digested and utilized for energy

The body’s stores carbohydrates as ‘glycogen’, which is present in the liver, and to a larger extent in the muscle. These glycogen stores are limited and can quickly get depleted. When carbohydrate availability (glycogen stores and blood glucose) become depleted, it is often referred to as ‘bonking’ or ‘hitting the wall’. If you have experienced this before, you became well aware of the extent this negatively impacted your exercise intensity/ capacity. You were likely forced to slow way down, and the work was likely perceived as far more challenging! This is due to the forced shift in substrate use- to fat and protein (fatty acids and amino acids). Since carbohydrates are the only substrate that can be used under anaerobic conditions, once it becomes depleted, the body is forced to shift to other substrates (fats and proteins) that can be used under aerobic conditions, which is why you are forced to slow down. Your body is in need of more oxygen to metabolize the alternative fuels once carbohydrate stores have become depleted.

Maximizing glycogen stores by proper fueling- before, during, and after exercise are all very important to keep your exercise performance high!

Daily Total Carbohydrate Needs for Distance Runners

Endurance athletes have a higher carbohydrate need compared to athletes of other sports.

It is not a good idea to use percentages of energy intake to assess carbohydrate needs since it does not consider if the athletes is meeting their energy needs. For instance, if an athlete aims for 65% of their total intake as carbohydrates, but falls short on their total energy intake, the total carbohydrates consumed (as 65%) would also fall short.  

It is important to get the majority of carbohydrates from nutritious foods that provide additional nutrient needs, such as vitamins, minerals, and fibers. Starchy vegetables, whole grains, fruits, legumes, and low fat dairy are all good choices of carbohydrates to include throughout the day. Carbohydrates that should be consumed sparingly and reserved for fuel during exercise include sugar sweetened beverages, candy, desserts, and generally- foods with added sugar. While the ‘eat sparingly’ foods are fine in moderation, they should not make up the majority of your carbohydrate needs. For athletes struggling to meet their carbohydrate needs despite including complex carbohydrates as part of healthy and balanced meals and snacks, incorporating simple sugars into their fueling strategies (i.e. before, during, after) may be helpful in meeting their target.

General Food Categories Offering a High Amount of Carbs

• Grains, all types

• Fruit and fruit juice

• Starchy Vegetables

• Milk and Milk Products

• Beans and Lentils

• Simple sugars: honey, agave, maple syrup, table sugar, molasses

• Desserts, candy and sugar containing beverages

• Sports gels and drinks

Before Exercise

Importance: Top of glycogen stores, and blood glucose availability for the start of the run. An overnight fast depletes liver glycogen stores- liver glycogen is important for supplying blood glucose. 

Amount and Timing: See table below for a general rule of thumb

Type: This comes down to individual tolerance; runners should consider: 

• Consistency (solid, liquid, etc)- liquids digest quicker than solids 

• Fiber content- you may tolerate high fiber foods if you’re used to eating them

• Simple sugar vs. starch content- this will impact fluctuations in blood sugar and satiety during your run 

• presence of other macronutrients- minimize fats, aim for ~10-20 g protein in pre-run meal 

• Volume- individual tolerance (primarily the result of factors listed above)

During Exercise

Importance: To help maintain blood glucose and spare muscle and liver glycogen; encourages/ augments fluid intake 

Type: Choose simple sugars vs. polysaccharides (starches) to high rates of oxidation (energy available faster). Carbohydrate containing sports drinks, sports gels and chews are ideal for maximizing readily absorbed and easily digestible carbohydrates for quick energy. Mixed sugars offer an advantage for maximizing absorption and oxidation rates; examples: glucose + fructose or glucose + sucrose, compared to solely glucose (including dextrose, maltodextrin- which are chains of glucose units) 

Amount and Timing: This depends on duration, intensity, and individual tolerance. See table below for a guide.

Tips:

• Start fueling early on, within the first 30 minutes 

• Spread out carbohydrate intake throughout your run for best tolerance 

• Aim to fuel every ~15-20 minutes; amount and frequency depends on total needs and tolerance

Different environments/ climates can impact your nutrition needs during exercise. Learn about about it here!

Post Exercise

Importance: Replenishes glycogen and energy stores to prepare for next run/ exercise session, assists in hydration 

Amount and Timing: If the next run or workout is in <8 hours, timing is very important! For the first 4 hours post run, consume 1-1.2g/kg/hr, then just stay in check with your daily carbohydrate recommendations (as displayed above) 

Type: Include some protein in your post exercise meal or snack. Complex carbohydrates are ideal, however, if unavailable, sports foods are better than not consuming any. Carbohydrate and protein needs during the post workout phase can be accomplished by a post run meal. If unable to consume a meal within a reasonable time, plan a quick and healthy snack- high in carbohydrates and moderate in protein. 

For post run snack and meal ideas, check out my recipe collection page. Here you will also find tips for making healthier choices when eating out!