Macronutrients for Running

Being health aware is on the rise, and more people are looking to ways to make themselves healthier. It is no surprise that eating a balanced diet will help guide us there, but incorporating one with an active lifestyle is the best way to maintain proper health. A great way to obtain a healthy body is with running due to its many proven health benefits. The American College of Sports Medicine claims that many health benefits are associated with changing from a sedentary lifestyle to even minimal activity, but that they are significantly increased when higher intensities and durations are reached (MedicineNet,n.d). Running can result in lower levels of triglycerides in the blood, higher levels of HDL, and low blood pressure. Running also improves aerobic fitness, which increases the levels of enzymes and hormones that allow efficient work of the heart and muscles (MedicineNet, n.d.). If one expects the body to run efficiently, it must be provided with the right fuel. Maintaining a diet balanced in carbohydrates, fat, and protein will allow an athlete to train to run at maximum performance. However, the caloric intake as well as the type of macronutrient ingested will affect performance as each one is interpreted by the body differently.

Carbohydrates are organic substances that include sugars, starches, and cellulose. The digestion of a particular carbohydrate in the gastrointestinal tract will depend on the complexity of the molecular structure of the carbohydrate (Collins,2007). Monosaccharides (glucose, fructose, galactose) are digested rapidly, while more complex carbohydrates such as cellulose or polysaccharides take longer to digest if digested at all.  The more complex carbohydrates are broken down by digestive enzymes to yield monosaccharides, which can be converted to glucose to be used to produce ATP, or energy. The process starts in the mouth by means of amylase, continues in the stomach, and finishes in the small intestine. The finished monosaccharide, glucose, is then absorbed into the blood stream via diffusion in the small intestine(Collins, 2007).The speed at which the carbohydrate is digested is determined by the chemical makeup of the carbohydrate, which will make it more or less resistant to the enzymes present in the body for the chemical breakdown. The simpler the carbohydrate, the easier it is to digest. However, the presence of an acid or a soluble fiber will slow down the digestive process (Collins,2007). Once in the blood stream, the glucose is then taken to the liver where it is either stored or distributed to cells for energy (Collins,2007). Excess glucose is converted here to glycogen, and is then stored here for later use.

Glycogen can quickly be broken down to supply glucose as needed. Glycogen is either stored in the liver or in the skeletal muscle cells. When liver glycogen is metabolized, it enters the blood stream as glucose and can be used any place the body needs it. Glycogen that is stored in the muscle is much more stable because it does not enter the blood stream. Glycogen stored in the muscle will only provide glucose for that muscle. When blood sugar levels fall, such as between meals, glycogenolysis takes place, and the glycogen is then converted back to glucose to produce ATP for energy. The hormone glucagon controls this response. When glycogen levels are no longer available, glucagon can trigger the transformation of amino acids or glycerol to glucose via the process of gluconeogenesis. Moderate to high intensity workouts get their main fuel source from glycogen stores in the muscle and liver and glucose in the blood. The liver can store up to 450 kilocalories of glycogen, while there are roughly 1,400 kilocalories of glycogen stored throughout the muscles (Bernadot, n.d.). Blood glucose is more limited than muscle and liver glycogen, but can be replenished more rapidly (, n.d.).

Digestion of fat takes longer than the digestion of proteins or carbohydrates. As fat leaves the stomach and enters the duodenum of the small intestine, bile is released into the small intestine, emulsifying any the fats. The emulsified fats are then split into fatty acids and glycerol, and can then be absorbed into the blood stream. During absorption, the fatty acids and glycerol combine with proteins to form chylomicrons, which are now soluble enough to enter the blood stream (RawFoodExplained,N.D.). The fatty acids are sent to the liver to be converted into acetate or ketone bodies as an energy source. Any leftover fat is stored as adipocytes in the adipose tissue. These storage sites are readily available to be converted to glucose for energy. Improving endurance training will increase the number and size of mitochondria inside cells, which will increase the capacity of the athlete to use fat during physical activity (Bernadot, n.d.). Because more fat is stored than carbohydrate, increasing fat utilization will allow a more efficient and longer-lasting use of carbohydrate utilization, increasing endurance.

During exercise, the athlete will move through both aerobic and anaerobic pathways of energy. Once exercise begins, ATP is produced anaerobically, but with an increase in oxygen, as the athlete will start to breathe heavier, aerobic metabolism begins. During moderate exercise, carbohydrate will undergo aerobic metabolism. During this time, oxygen is present and the carbohydrate will undergo both the Embden-Meyerhoff pathway and the Krebbs cycle to result in maximum energy from glucose molecule (Connelly, n.d.). When there is plenty of oxygen available, aerobic metabolism will produce 42 ATP, along with the by-products carbon dioxide and water. Anaerobic metabolism produces only 4 ATP, but provides energy more rapidly as it uses local glycogen stores in the muscle. Anaerobic glycolysis supplies energy for most short-term intense exercise ranging from 30 seconds up to 2 minutes. A by-product of anaerobic metabolism is lactic acid, which leads to fatigue and muscle cramps. Lactic acid can be taken up by the liver to be converted back to glucose to be circulated in the blood for usage by the muscles(Connelly, n.d.). Lactic acid can also be used by cardiac muscles or by less active skeletal muscles.

During less intense workouts, such as mild jogging or brisk walking, fat is the primary source of fuel because the supply of ATP is enough to maintain the intensity. Fatty acids are readily available in the form of fatty acids in the blood or as storage in adipose tissue. Fat is not a useful fuel for short-term high intensity exercises, but can be used as the sole fuel for low or moderate intensity workouts. Fat provides a store of easily utilized calories for fuel. Also, when comparing the number of ATP produced per carbon atom, fat is more efficient. A 6-carbon glucose molecule produces 36-38 ATP, resulting in 6 ATP/Carbon, while an 18-carbon fatty acid produces 147 ATP resulting in a ratio of 8.2 ATP/Carbon. However, when amount of ATP per unit of oxygen consumed is considered, carbohydrate is more efficient. Six oxygen molecules of oxygen are required to convert 6-carbon glucose to produce 36 ATP, resulting in 6 ATP/Oxygen, whereas to produce 147 ATP from 18-carbon fatty acids, 26 oxygen molecules are needed, resulting in 5.7 ATP/Oxygen (Connelly, n.d.).  Therefore, for a runner, it is important to maintain an abundance of carbohydrates in the diet to maintain glycogen stores in the body. This will allow an efficient mixture of fat and carbohydrate to be used as fuel for the body.

Proteins are also an important nutrient for maintaining a healthy and efficient body. Once ingested, protein digestion will start in the stomach by the presence of hydrochloric acid and the enzyme pepsin (CarbSmart,2007). The rate at which protein is digested depends on the concentration of the enzyme, the amount, temperature, and acidity of the food, and the presence of inhibitors such as antacids. The protein is broken down in the stomach to smaller parts known as amino acids. Digestion will continue in the small intestine by the presence of tripsin and chymotripsin, and once complete, the amino acids will be absorbed into the blood stream via diffusion and will then be carried to the liver for processing before being distributed into general circulation (CarbSmart,2012).

Protein only provides roughly 6% of energy needs, but can increase up to 10 or 15% during high intensity endurance exercise (Connelly, n.d.). Certain amino acids can be converted to glucose and further metabolized to produce ATP, while others can be stored as fat to later be catabolized to yeild ATP. The liver is the primary source for protein synthesis. It consistently monitors protein needs and will synthesize amino acids and proteins to satisfy any requirements (Benardot, n.d.). As protein is not an efficient use of fuel for energy, it essential that athletes consume enough carbohydrates to spare the utilization of protein for energy, so that the protein can be used for other more important functions. Studies have shown that the maximal rate of protein utilization for nonenergy uses is 1.5 g of protein per kilogram of body weight. When this amount is exceeded, the body will do several things to the excess protein available. Either stored as fat or used as energy, the nitrogen present in the amino acids must be removed from the body. It is important for athletes to remain nitrogen-balanced, as a positive or negative fluctuation will affect performance. A negative nitrogen balance indicates that the body is expelling more nitrogen than being consumed, which indicates muscle loss. A positive nitrogen balance indicates an increase in muscle tissue (Benardot, n.d.). Protein can be oxidized during short-term, intense workouts, but the amount is insignificant. During endurance exercise, however, protein will contribute 3-5% of total energy needs. If glycogen or blood sugar levels are low, exercise intensity is high or the duration is long, protein can contribute over 5% of total energy needs (Benardot, n.d.). If the athlete wanted to increase pure muscle mass, an increase in protein will have to be consumed. Any additional calories needed to support a larger muscle mass should include a proportionate increase in protein. An increase in protein intake would have to be coupled with the proper exercises that increase muscle mass, such as strength-building. Otherwise, the extra calories will then store themselves as fat instead of muscle. It is possible to use protein as a main energy source, but breaking down protein for energy leaves undesirable nitrogen waste, which makes the process very inefficient.

Running is a sport that can be very demanding of the body. Because of this, it is important that the right diet is consumed to ensure efficient bodily processes. Because running requires a lot of food for fuel, it is important that a runner diet be predominantly carbohydrates, or about 60% of daily calories. 25% should be from fat, and 15% from protein. As a runner, it is important that enough of each macronutrient is obtained, but it is also important to not over do it, as this can lead to unintentional weight gain. A diet that is in this ratio will ensure a steady blood sugar level that will allow for a fast recovery after training (Davis,2010). Carbohydrate sources should come from healthy foods such as fruits, vegetables and whole grains. Good protein sources include eggs, chicken, turkey and tofu. It is most beneficial to get your fat intake from unsaturated fats, such as fish, seeds and nuts (Davis,2010). It is also essential that you time your carbohydrate intake right. Carbohydrates are needed before and after workouts. They are needed before the workout to provide fuel to sustain enough energy, and after the workout to replenish the glycogen stores in the body and to prevent energy levels from dropping later. Carbohydrates should be consumed within two hours after running, and 100-200g should be consumed, as recommended by Iowa State University Extension. It is also important to choose nutrient-dense foods, such as whole grains, brown rice, and whole wheat bread, as they will provide more minerals, vitamins and antioxidants (Davis, 2010). Fluids should also be consumed before, during, and after any physical activity. At least 17-20 fluid ounces of water should be consumed with each meal, to ensure proper digestion and to prevent dehydration. Electrolytes should also be replenished to facilitate bodily processes. Ensuring that a runner, or any athlete, balances the appropriate diet with the right training is key to success in obtaining both optimal training and performance.

Works Cited

Benardot, Dan. Advanced Sports Nutrition. Champaign, IL: Human Kinetics, 2006. Print.

“Catabolic vs Anabolic.” Burn Fat And Gain Muscle, Body Building, Fitness Training & Nutition. Web. 14 Feb. 2012. <;.

Collins, Anne. “Digestion of Carbs: How Carbohydrate Is Digested.” Weight Loss Diet Program, FREE Diet Advice! Weight Loss Diets, Low Carb Plan. Web. 13 Feb. 2012. <;.

“Energy Pathways for Exercise – Aerobic and Anaerobic Metabolism.” Sports Medicine, Sports Performance, Sports Injury – Information About Sports Injuries and Workouts for Athletes. Web. 14 Feb. 2012. <;.

“Fats – Fat Digestion.” Raw Food Living|Raw Food Diet & Recipes|Organic Raw Foods. Web. 13 Feb. 2012. <;.

Gruber, Dr. Beth. “Protein Digestion | Digestion of Proteins | Protein Absorption.” Get “Carb Smart” at CarbSmart®! Low Carb Foods, Sugar Free, & Diabetic Foods. Web. 13 Feb. 2012. <;.

Gruber, Dr. Beth. “Protein Digestion | Digestion of Proteins | Protein Absorption.” Get “Carb Smart” at CarbSmart®! Low Carb Foods, Sugar Free, & Diabetic Foods. Web. 14 Feb. 2012. <;.

“Lecture 6-Fuel Utilization During Exercise, Aerobic and Anaerobic Metabolism, Control of Muscle Protein Metabolism/Anabolism Pg1.” Web. 13 Feb. 2012. <;.

“Racing Weight – Nutrition for Muscle Recovery.” Untitled Page. Web. 13 Feb. 2012. <;.

“Running Symptoms, Causes, Treatment – Why Run? on MedicineNet.” Web. 13 Feb. 2012. <;.

“Training Diet For Runners | LIVESTRONG.COM.” LIVESTRONG.COM – Lose Weight & Get Fit with Diet, Nutrition & Fitness Tools | LIVESTRONG.COM. Web. 13 Feb. 2012. <;.

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