Written by: Kevin Cann
Carbohydrate loading is a dietary means that has been used to improve performance in endurance athletes. The theory behind carbohydrate loading is to maximize the stored amount of carbohydrates in our body, as glycogen, to yield more energy. This is done in two steps. The first step is to adjust carbohydrate intake for a week to between 50-55% of total daily calories. Fat and protein are increased to make up for any differences in caloric intake. Training remains the same. This allows the athlete to dump the stored glycogen he or she already has and make room for the second step. The second step takes place about 3-4 days from the event. This step calls for increasing carbohydrate intake to about 70% of daily calories. Foods that contain higher amounts of fat are decreased and training is decreased as well (Mayo Clinic staff, 2011). Is this truly the safest and most effective way for endurance athletes to fuel their bodies leading up to a race?
In a study done by Rauch in 1995, he tested the pre-exercise muscle glycogen content as well as performance in endurance trained cyclists after a three day carbohydrate loading protocol. The study concluded that the carbohydrate loading group increased pre-exercise muscle glycogen content as well as power output and total distance covered in one hour (Rauch, 1995). This study proves that carbohydrate loading has positive effects on performance. More importantly it shows that having maximized glycogen stores can increase performance.
In another study done by Lambert in 2001 they tested a high fat diet and a habitual diet before a carbohydrate loading protocol. This study showed that the high fat diet group increased performance greater than the group on the habitual diet before a carbohydrate loading phase. The study also concluded that the high fat group increased performance while having a higher reliance on fats as energy (Lambert, 2001). Any exercise lasting longer than 240 seconds requires glycogen as well as fatty acids for energy (NASM, 2010). These studies combined state that maximizing glycogen stores while increasing our reliance on fatty acids can increase overall performance in endurance athletes. Increasing carbohydrates in the diet can come with a lot of negative consequences as well.
When endurance athletes add carbohydrates to their diets they typically will add grains in the form of breads and pastas. This can be hazardous to the health of the athlete for a number of reasons. Some grains such as; wheat, rye, and barley, (and usually oats due to cross contamination) contain a commonly problematic protein composite called gluten. Gluten is partially made up of storage proteins called prolamins. While some other grains technically don’t contain gluten, they have their own simlar prolamins as well, which can be problematic for many people. Most prolamins are formed from repetitive amino acid sequences that contain high amounts of glutamine and proline. Examples of prolamins are gliadin found in wheat and avenin found in oats. Gluten and these prolamins can cross the intestinal barrier and also cause an inflammation response. The tests for gluten sensitivity actually look at antigliadin antibodies in the blood. The prolamins and gluten entering the blood stream can also lead to auto-immune disease in susceptible people. The protein zonulin is in control of regulating our intestinal permeability. Eating foods high in prolamins and gluten will increase the amount of zonulin in our intestines. This creates extra spaces for undigested proteins to pass through. Our bodies will treat these undigested proteins as dangerous and launch an immune response. The antibodies that are created can then attack other systems in our bodies. This can lead to disease as well as inflammation in areas such as the athlete’s joints. Training for endurance sports already causes inflammation and the diet needs to counteract that.
Another problem with eating grains is the increased amounts of phytic acid. Phytates are substances that bond to the metals; iron, zinc, calcium, and magnesium in our bodies. This does not allow for the minerals to be absorbed and used properly. One study conducted by Davidsson in 1994 showed that decreased amounts of phytic acid in baby formula increased the bioavailability of iron and zinc (Davidsson, 1994). Iron is especially important in endurance athletes because it supplies the protein hemoglobin in red blood cells which are responsible for carrying oxygen to the working tissues. According to the USDA, endurance athletes are more prone to iron deficiency. Diet should not further that deficiency, but supply the body with correct nutrients to avoid a deficiency.
Zinc is responsible for cellular respiration, DNA reproduction, maintaining cell membranes, and clearing out free radicals. Micheletti stated in the Sports Medicine Journal that increased amounts of carbohydrates as well as decreased amounts of fats and proteins lead to deficiencies in the mineral. The deficiencies in athletes can lead to decreased bodyweight, fatigue, and increase the risk of osteoporosis (Micheletti, 2001).
Calcium, magnesium, phosphorous, and iron are also important in bone formation. Athletes are at an increased risk for stress fractures (Clarkson, 1995). This is especially true for endurance athletes that log a lot of miles per week in training. Maximizing absorption of all these minerals is important to keeping the athlete healthy.
These are not the only issues associated with carbohydrate loading. Every person is different. A common side effect for ingesting an increased amount of carbohydrates is gastrointestinal distress. This can severely hinder performance in athletes. According to the NIDDK the body does not breakdown some carbohydrates because of the lack of certain enzymes. As this undigested food passes through the intestines gasses such as hydrogen, carbon dioxide, and methane are produced. This can cause gas and bloating in the athlete, which also can affect performance (NIDDK, 2011).
There is a better and healthier way to go about maximizing glycogen stores, increasing the body’s reliance on fat as energy, and increasing absorption of key minerals while also decreasing bouts of bloating, gas, and gastrointestinal discomfort. To maximize glycogen stores, glycemic loading is effective. Ingesting high glycemic carbohydrates 30 minutes post exercise can help the athlete replenish lost glycogen. Cordain recommends taking in .75g of carbohydrates per pound of bodyweight. Instead of consuming breads and pastas that are high in antinutrients and undigestable proteins the athlete should consume high glycemic fruits or sweet potatoes. For endurance athletes that took part in more demanding exercise this should be repeated about 90 minutes to two hours following the workout due to the continued burning of muscle glycogen during recovery. The athlete also needs to rehydrate and consume protein in a 4:1 carbohydrate to protein ratio (Cordain, 2002).
To increase nutrient and mineral absorption the rest of the day the athlete should stick to lean meats, fish, eggs, fruits, and vegetables. Preferably the meats will be grass fed to contain higher amounts of omega 3 fatty acids. This coupled with eating wild caught seafood can increase the athlete’s amounts of ingested omega 3 fatty acids and help fight inflammation. Also, adding healthy fats to the diet can increase performance by increasing the body’s ability to rely on those fats for energy. Grass-fed meats as well as wild caught fish are also great for this. To increase fats more in the diet olive oil can be used in salad dressings or sprinkled on vegetables. Foods can also be cooked in coconut oil to reap the health benefits of the medium chain fatty acids. Fruits and vegetables are second to no foods in vitamins and minerals and are also important to keeping the athlete healthy as well as aiding in recovery.
Endurance sports increase the amount of oxygen that is utilized by the body. This also increases the amount of free radicals in the system. These free radicals can cause harm to tissues and hamper cellular repair (Witt, 1992). This makes it even more important for the endurance athlete to be getting proper nutrition. High carbohydrate diets that lean on grains for calories can decrease the absorption of these important nutrients and lead to the athlete breaking down.
In conclusion, an endurance athlete needs to be aware of the negative implications food choices can have on performance. A carbohydrate loading protocol that leans on grains for calories can hinder recovery and performance. Studies have shown that maximizing glycogen stores while increasing the body’s reliance on fat for energy can increase performance. This can be accomplished by eating high glycemic foods post workout and eating a diet that is rich in lean meats, fish, eggs, fruits, and vegetables.
Witt, EH (1992). Exercise, oxidative damage and effects of antioxidant manipulation. www.pubmed.gov. Retrieved on January 14, 2012.
NIDDK (2011). Gas in the Digestive System. www.digestive.niddk.nih.gov. Retrieved on January 14, 2012.
Clarkson, Priscilla (1995). Exercise and mineral status of athletes. Journal of the American College of Sports Medicine. Retrieved on January 14, 2012.
Davidsson, L (1994). Iron bioavailability studied in infants: the influence of phytic acid and ascorbic acid in infant formulas based on soy isolate. www.ukpmc.ac.uk. Retrieved on January 14, 2012.
Lambert, EV (2001). High-fat diet versus habitual diet prior to carbohydrate loading: effects of exercise metabolism and cycling performance. www.ukpmc.ac.uk. Retrieved on January 14, 2012.
Mayo Clinic Staff (2011). Carbohydrate Loading Diet. www.mayoclinic.com. Retrieved on January 14, 2012.
Rauch, LH (1995). The effects of carbohydrate loading on muscle glycogen content and cycling performance. Retrieved on January 14, 2012.
Micheletti, A (2001). Zinc status in athletes: relation to diet and exercise. Sports Medicine Journal. Volume 31 Number 8. Retrieved on January 14, 2012.
Cordain, Loren (2005). The Paleo Diet for Athletes. Rodale Publishing. Retrieved on January 14, 2012.
NASM (2010). NASM Essentials of Sports Performance Training. Lippincott, Williams, and Wilkins. Baltimore, MD.
Kevin is owner of Genetic Potential Nutrition. He is a holistic nutritionist, wellness coach, and strength coach. He works with people fighting illness, to competitive athletes. Check out his site at www.geneticpotentialnutrition.