NUTRITION - Carbohydrates for a soccer player
Carbohydrates have an important role within the human body. Glycogen, which is how carbohydrates are stored in the muscle and liver, provide the energy needed for contracting muscles (Jeukendrup & Gleeson, 2018). Glycogen in the liver is the main source for maintaining blood glucose levels, while glycogen in the muscle provides immediate energy to the muscles during high intensity exercise or exertion (Kanungo et al., 2018). Therefore, while exercising, both muscle glucose and liver glucose uptake increases. If there is not enough fuel, through exogenous carbohydrates, the glucose supply cannot keep up the demand, resulting in glycogen depletion, which can lead to hypoglycemia (Jeukendrup & Gleeson, 2018). Hypoglycemia can result in symptoms of increased heart rate, disorientation, fatigue, and reduced mental awareness to name a few. Many of these symptoms can subside with consuming carbohydrates (Jeukendrup & Gleeson, 2018; Middleton & Balan, 2012). What’s more, side effects of hypoglycemia become less prevalent when carbohydrates are taken closer to exercise, because the small window of time does not allow for insulin levels to increase (Jeukendrup & Gleeson, 2018).
Our subject, Arlene, is a soccer player, who will naturally engage in many eccentric muscle contractions. Eccentric contractions, especially at a higher intensity can slow down the rate of muscle glycogen resynthesis (Glycogen replenishment after depletion from exercise) (Jeukendrup & Gleeson, 2018). Jeukendrup & Gleeson (2018) also state that several studies done on soccer players showed that glycogen restoration took much longer, even for those on a high carbohydrate diet already. They continue by suggesting that by adding in higher amounts of carbohydrates into the diet can aid in the compromised glycogen resynthesis (Jeukendrup & Gleeson, 2018).
Arlene is also experiencing stomach cramps while ingesting juice, because she does not like the taste of many sports drinks. Many juices contain fructose, which can cause stomach cramps and other gastrointestinal disturbances. However, when consuming a combination of fructose and glucose, this can help mitigate these disturbances (Jeukendrup & Gleeson, 2018; Pepin et al. 2019). Pippin et al. (2019) also states that glucose can inhibit gastric emptying, in comparison to fructose and carbohydrate polymers. This fact has to do with how different carbohydrates have separate transport mechanisms (Jeukendrup & Gleeson, 2018). For example, glucose is transported by a glucose transporter called SGLT1, while fructose is transported by GLUT5. Ingesting high quantities of a single carbohydrate can cause the transporters to become saturated, which will not aid in an increased oxidation rate. A study cited by Jeukendrup & Gleeson (2018) saw higher oxidation rates when glucose and fructose were mixed together, and resulted in less gastrointestinal stress, than glucose alone (Jeukendrup & Gleeson, 2018).
Arlene's goal is to lose weight, while also gaining back her speed and endurance. Therefore, we need to look at timing, consumption, type of carbohydrates, and total energy expenditure. Arlene is engaging in 2-3 hour practices and weekend games. Assuming that practice is held after school, Arlene is engaging in moderate to high intensity exercise 4-6 times a week. The recommended amount of carbohydrates for someone of this level needs over 10 grams/kg/body weight/day of carbohydrates (Jeukendrup & Gleeson, 2018). Since Arlene is trying to lose weight, choosing nutrient rich carbohydrates/meals that contain protein can result in a lower caloric amount and also promote additional glycogen recovery (Jeukendrup & Gleeson, 2018). What’s more, a study from Van Loon et al. (2000) mixed a protein hydrolysate and amino acid mixture that combined .8 grams/kg/body weight/hour of carbohydrates and .4 grams/kg/body weight/hour of protein. This mixture resulted in a higher glycogen resynthesis (Van Loon et al., 2000, as cited by Jeukendrup & Gleeson, 2018).
About 3-5 hours before practice or a game, Arlene should consume approximately 140-330 grams of carbohydrates, depending on her total weight. This will help improve her performance by increasing muscle glycogen levels (Jeukendrup & Gleeson, 2018). This is especially important when Arlene has morning practices and games, because the liver becomes depleted of glycogen after fasting overnight, while sleeping. As Arlene gets closer to a practice or a game, ingestion of some carbohydrate is also important. However, this also has to do with personal preference. As stated above, side effects of hypoglycemia become less prevalent when carbohydrates are taken closer to exercise, because the small window of time does not allow for insulin levels to increase. However, some athletes may experience gastrointestinal stress. Since this is already an issue for Arlene, she should monitor her intake of carbohydrates before her practices. Additionally, It is also important for Arlene to consume some carbohydrates during practice as well. When exercise sessions last longer than 45 minutes, adding in carbohydrates can help improve endurance performance. Ingesting carbohydrates during exercise can help maintain blood glucose levels and high levels of carbohydrate oxidation (Jeukendrup & Gleeson, 2018). A great option here is a sports drink, but as previously stated, Arlene does not enjoy the taste of sports drinks and juice gives her stomach cramps. Suggesting an electrolyte mix, containing different types of carbohydrates could be a solution for Arlene. Lastly, after practices and games, Arlene needs to refuel, and replenish her depleted stores of liver and muscle glycogen. 6-10 grams of carbohydrates are recommended for an athlete engaging in 1-3 hours of moderate to high intensity exercise (Jeukendrup & Gleeson, 2018).
In conclusion, Arlene should increase her carbohydrate intake to improve her speed and endurance performance. Including nutrient rich carbohydrates that include protein can also aid in glycogen resynthesis. Developing a schedule for when she consumes these carbohydrates will greatly help her energy levels, increasing her total energy expenditure, by improving her overall performance and eliminating fatigue. These factors will also help Arlene with her goal of losing weight.
References
Jeukendrup, A. E., & Gleeson, M. (2018). Sport nutrition (3rd ed.)
Kanungo, S., Wells, K., Tribett, T., & El-Gharbawy, A. (2018). Glycogen metabolism and glycogen storage disorders. Annals of Translational Medicine, 6(24), 474. https://doi.org/10.21037/atm.2018.10.59
Pepin, A., Stanhope, K. L., & Imbeault, P. (2019). Are fruit juices healthier than sugar-sweetened beverages? A Review. Nutrients, 11(5), 1006. https://doi.org/10.3390/nu11051006
Middleton, S. J., & Balan, K. (2012). Idiopathic accelerated gastric emptying presenting in adults with post-prandial diarrhea and reactive hypoglycemia: a case series. Journal of Medical Case Reports, 6, 132. https://doi.org/10.1186/1752-1947-6-132
