Chapter 1: The Nutrients
Overview
Nutrition is an important factor in influencing one’s performance since it is able to provide energy, assist tissue growth and repair, and regulate metabolism or cellular respiration (Coleman, 1996). Athletes are required to take the right fuel in order to have enough energy for training and competition as well as for staying healthy. Athletes need to know what foods are important for energy and for replenishing their bodies, when to eat certain foods, how to eat for a specific event, and what specific foods will improve their performance in their sport (Litt, 2004).
Nutrients
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There are many types of nutrients, each of which has a specific function in nourishing the body. The key nutrients are carbohydrates, proteins, fats, vitamins, minerals and water (Litt, 2004).
Macronutrients
Macronutrients include carbohydrates, proteins, and fats, which supply the body with the calories used for energy. Regardless of age and gender, the body burns a certain number of calories daily in order to stay alive. The resting metabolic rate (RMR) is the amount of calories that one’s body would burn if he or she stayed in bed all day. The calories burned would be used for automatic body functions such as fueling the heart to pump blood. Calories are also burned through exercises. The longer and more intense the exercise, the more calories that are required by the body. When an athlete does not consume enough calories, their metabolism will slow and they will have less energy to perform and to grow properly (Litt, 2004).
Macronutrients
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As seen in the following table, one gram of fat supply more than double the amount of calories that one gram of carbohydrates or one gram of protein would provide.
Amount of Calories in Macronutrient
1 gram of carbohydrates
|
4 calories
|
1 gram of protein
|
4 calories
|
1 gram of fat
|
9 calories
|
(Litt, 2004)
Carbohydrates
There are two types of carbohydrates: simple and complex carbohydrates (Litt, 2004).
Simple carbohydrates consists of only one or two glucose units named as monosaccharides and disaccharides (Litt, 2004). These are found in sweet foods such as fruits, honey, and cereals. These could also be found in unhealthy foods like table sugar, candy, chocolate, soda, jam, and white bread which should be avoided (FITDAY, 2013, http://www.fitday.com/fitness-articles/nutrition/carbs/simple-vs-complex-carbohydrates.html#b; Litt, 2004). Simple carbohydrates are easily digested and absorbed and are, therefore, a good source for immediate fuel; however, simple carbohydrates are not effective in helping one to sustain energy (Litt, 2004).
Simple Carbohydrates
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Complex carbohydrates are polysaccharides and are commonly referred to as starch. These are found in foods such as spinach, broccoli, zucchini, oatmeal and whole wheat breads (FITDAY, 2013, http://www.fitday.com/fitness-articles/nutrition/carbs/simple-vs-complex-carbohydrates.html#b; Litt, 2004). Complex carbohydrates are digested and absorbed at a slower rate than simple carbohydrates and are, therefore, a source of long-term energy. They also provide the body with calories and fiber (Litt, 2004).
Complex Carbohydrates
A minimum of 50 percent of the calories that one consumes should be in the form of carbohydrates. Carbohydrate is the primary fuel for the body as it is a source of energy that the muscles prefer to use. All carbohydrates are broken down into glucose to go through cellular respiration, a process that produces energy for the body in the form of ATP (Litt, 2004).
The process of cellular respiration is a catabolic reaction, for which the energy required by the body is formed by breaking down glucose. Glucose is the primary fuel of the process. The energy formed is ATP, adenosine triphosphate, a form which the cells are able to use (Fraser, 2012; Freudenrich, 2014, http://health.howstuffworks.com/wellness/diet-fitness/exercise/sports-physiology5.htm; LIVESTRONG.COM, 2014, http://www.livestrong.com/article/187459-how-does-exercise-affect-the-rate-of-cellular-respiration).
The overall equation of the reaction is C6H12O6 + 6O2 → 6CO2 + 6H2O + 36ATP. One molecule of glucose and six molecules of oxygen gas produce six molecules of carbon dioxide, six molecules of water, and 36 ATP (Fraser, 2012; Freudenrich, 2014, http://health.howstuffworks.com/wellness/diet-fitness/exercise/sports-physiology5.htm; LIVESTRONG.COM, 2014, http://www.livestrong.com/article/187459-how-does-exercise-affect-the-rate-of-cellular-respiration).
Cellular respiration or cellular metabolism can be aerobic or anaerobic. Aerobic respiration occurs in the presence of oxygen, while anaerobic respiration occurs in the absence of oxygen. The type of respiration the body uses depend on the intensity and duration of the exercise. In short and intense exercises, the anaerobic respiration is used because the body uses oxygen faster than it can be supplied to the cells of the body. Aerobic respiration does not occur as fast as anaerobic respiration, but it can supply ATP for hours, so it is used in long-duration exercises. Cellular respiration is separated into four steps: glycolysis, pyruvate oxidation, Krebs cycle, and the electron transport chain (Fraser, 2012; Freudenrich, 2014, http://health.howstuffworks.com/wellness/diet-fitness/exercise/sports-physiology5.htm; LIVESTRONG.COM, 2014, http://www.livestrong.com/article/187459-how-does-exercise-affect-the-rate-of-cellular-respiration).
The Stages of Cellular Respiration
Glycolysis is an anaerobic process and occurs in the cytoplasm of a cell. It breaks each glucose molecule into two 3-carbon pyruvate molecules. In this step, two ATP and two electron carriers NADH are formed for each glucose molecule. The overall reaction is glucose + 2NAD+ + 2ADP + 2Pi → 2pyruvate + 2H+ + 2NADH + 2ATP (Fraser, 2012; Gregory, n.d., http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20101/bio%20101%20lectures/cellular%20respiration/cellular.htm).
Glycolysis
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In pyruvate oxidation, pyruvate is transported to the mitochondrial matrix and converted into a 2-carbon molecule. One carbon is released as carbon dioxide for each pyruvate molecule. The product, acetyl group, binds with the coenzyme-A to form acetyl-CoA. The CoA carrier is required for the acetyl group to cross the inner mitochondrial membrane since the inner membrane does not have pores that are large enough to allow diffusion like the outer mitochondrial membrane does. The overall reaction is 2pyruvate + 2NAD+ + 2CoA → 2acetyl-CoA + 2NADH + 2H+ + 2CO2 (Fraser, 2012; Gregory, n.d., http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20101/bio%20101%20lectures/cellular%20respiration/cellular.htm).
Pyruvate Oxidation
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Krebs cycle is an anaerobic process and occurs in the mitochondrial matrix. For every acetyl-CoA molecule, three electron carriers NADH, one electron carrier FADH2, two carbon dioxide molecules, and one ATP from substrate level phosphorylation are formed. Once this step is completed, coenzyme-A is released and participates again in pyruvate oxidation. The overall reaction is acetyl-CoA + 3NAD+ + FAD + ADP + Pi → 2CO2 + 3NADH + 3H+ + FADH2 + ATP + CoA (Fraser, 2012; Gregory, n.d., http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20101/bio%20101%20lectures/cellular%20respiration/cellular.htm).
Krebs Cycle
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The three anaerobic stages do not produce nearly as much ATP as the body requires. Oxidative phosphorylation will produce the majority of the ATP the body needs. This aerobic stage is called the electron transport chain and occurs across the inner mitochondrial membrane. There are four protein complexes embedded in the membrane. The electron carrier NADH donates its electrons at the first protein complex and the electron carrier FADH2 donates its electrons at the second protein complex. These electrons are facilitated by the electron shuttle ubiquinone and cytochrome C to arrive at the extremely electronegative electron acceptor, oxygen, which diffused into the mitochondria when it reached the muscle cells through the bloodstream. When the electrons were donated, hydrogen ions were also lost from those electron carriers. These hydrogen ions are actively transported from the matrix into the intermembrane space by the protein complexes. The inner membrane restricts the passage of hydrogen ions, so a proton gradient is set up across the membrane. The hydrogen ions can only cross the ATP synthase to return the matrix. The passage of hydrogen ions through the ATP synthase powers the ATP synthase to begin the oxidative phosphorylation of ATP from ADP. The hydrogen ions inside the matrix then form water with the oxygen as well as the electrons from the electron carriers. This aerobic process produces many more ATP than the other three stages, as seen in the following table (Fraser, 2012; Gregory, n.d., http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20101/bio%20101%20lectures/cellular%20respiration/cellular.htm).
The Electron Transport Chain
Important Products Produced in the Four Stages of Cellular Respiration
Stages
|
ATP
|
NADH
|
FADH2
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CO2
|
Location
|
Glycolysis
|
2
|
2
|
0
|
0
|
Cytosol
|
Pyruvate Oxidation
|
0
|
2
|
0
|
2
|
Mitochondrial membrane
|
Krebs Cycle
|
2
|
6
|
2
|
4
|
Mitochondrial matrix
|
Electron Transport Chain
|
32-34
|
0
|
0
|
0
|
Inner mitochondrial membrane
|
(Fraser, 2012)
Glucose serves as an important fuel for athletes. It is converted to glycogen and stored in the liver and muscles when it is not used. Training and diet affects the amount of glycogen that the body is able to store. Excess carbohydrates that are not converted into glycogen are stored as fats (Litt, 2004).
Two athletes of the same age, but different weight and height cannot follow general food guide recommendations to consuming carbohydrates. A gymnast would be required to take different amounts of carbohydrates than a weightlifter. A weightlifter would need to consume much more carbohydrates in a day in order to fuel their muscles while a gymnast will require less in order to maintain figure. Both athletes cannot eat the same foods and both expect success. Chapter four will discuss more about the differences in the nutrient requirements for different types of athletes (Castle, 2014, http://www.livestrong.com/article/111192-gymnasts-diet/; Stark, 2014, http://www.livestrong.com/article/142593-nutrition-meal-plan-weight-lifters/).
Carbohydrates are the primary source of energy for the body. In other words, the body prefers to use glucose over proteins and fats for energy. In fact, carbohydrates provide more than 60 percent of the amount of energy required by the body (FITDAY, 2013, http://www.fitday.com/fitness-articles/nutrition/carbs/simple-vs-complex-carbohydrates.html#b; Litt, 2004). The energy is mostly used for normal body functions such as heartbeat, digestion, breathing and body movements. Fats and protein can be converted to glucose if the body is depleted of glycogen stores (FITDAY, 2013, http://www.fitday.com/fitness-articles/nutrition/carbs/simple-vs-complex-carbohydrates.html#b). In chapter three, the consequences of a low carbohydrate diet will be covered in more detail.
Protein
Protein is especially important for athletes because it helps the body to build and repair muscle tissues after an injury or exercise. Seafood, milk, cheese, yogurt, eggs, beans, and soy are all good sources of proteins (WebMD, 2013, http://www.webmd.com/fitness-exercise/guide/good-protein-sources). Protein can be found in all cells of the body, such as hair and skin. Protein is also responsible for growth, regulating body functions, and fighting infections. Protein is made of smaller molecules called amino acids. There are 20 types of amino acids that the body combine in various sequences to produce proteins that the body require. The body can make 11 of those 20 amino acids, and the other nine are called essential amino acids that must be obtained from food. Much like carbohydrates, the protein can also act as a source of fuel. However, it is only used when the body is depleted of carbohydrates and fats, as protein’s primary function is in building and repairing the body and not in providing the body with energy. A lack of protein may cause growth problems, loss of muscle mass, decreased immunity, weakened heart and respiratory system, and even death. It is important to consume an adequate amount of protein every day (Harvard School of Public Health, 2014, http://www.hsph.harvard.edu/nutritionsource/what-should-you-eat/protein/; Litt, 2004).
Sources of Protein
A gymnast and a weightlifter should not follow a general food guide that tells them the amount of protein they need to consume. A weightlifter would need to consume much more protein each day to help with muscle growth and repair. A gymnast will require less protein because they have smaller muscle masses that only need to be maintained and repaired from workouts. Both athletes will not succeed if they followed a general guide as their different body sizes require different amounts of nutrients (Castle, 2014, http://www.livestrong.com/article/111192-gymnasts-diet/; Stark, 2014, http://www.livestrong.com/article/142593-nutrition-meal-plan-weight-lifters/). Chapter four will discuss more about the differences in the nutrient requirements for different types of athletes.
Fats
Avocado, nuts, soy, tofu, and meat and dairy products are all good sources of fats. Potato chips, ice-cream, candies, cookies, and cakes are sources of unhealthy fats and should be avoided. Dietary fats are necessary for absorbing fat-soluble vitamins, protecting organs, and providing insulation (FITDAY, 2013, http://www.fitday.com/fitness-articles/nutrition/carbs/simple-vs-complex-carbohydrates.html#b). They are also important in making people feel full. Those who consume low-fat diets do not obtain enough calories to support growth and always feel hungry (Litt, 2004).
Sources of Fat
It is a common misconception for people to think that all fats are unhealthy and that consuming large amounts of fat lead to all kinds of diseases such as heart attacks and obesity; however, it is really the type of fat that is making an effect than the amount of fat intake.
The process of partial hydrogenation was discovered in 1901 by the German chemist Wilhelm Normann. The process converts vegetable oil into substances such as margarine and produces trans fats as a by-product. This invention was popular since it was a cheaper as well as a longer-lasting alternative to the traditional cooking fats. It also enhanced the flavour, texture and shelf life of processed foods (WebMD, 2014, http://www.webmd.com/food-recipes/understanding-trans-fats).
Sources of Trans Fats
Partially hydrogenated oils are the primary source of trans fats and are no longer regarded as safe by the U.S. Food and Drug Administration, in November 2013. The imposed rule will eliminate all industrially produced trans fats, saving thousands of lives each year. In one study, it was discovered that women who had the highest trans fats intake had a 50 percent higher risk to coronary heart disease. In another research done by the Dutch researcher, Martijn Katan, and his colleagues, it was found that both trans fats and saturated fats increased one’s bad LDL, low-density lipoprotein, cholesterol. However, trans fats also lowered the good HDL, high-density lipoprotein, cholesterol level. Trans fats are considered the worst type of fat by some doctors as it can lead to major health problems. A high LDL cholesterol level combined with a low HDL cholesterol level increases one’s risk of heart diseases (Mayo Clinic, 2014, http://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/in-depth/trans-fat/art-20046114; CBC News, 2013, http://www.cbc.ca/news/business/u-s-trans-fats-ban-puts-pressure-on-health-canada-1.2472351).
Lipids are non-polar molecules and do not dissolve in water. Each fatty acid chain consists of a hydrocarbon chain attached to a carboxyl group (-COOH) which gives the fatty acid its acidic properties. The fatty acid is saturated if the hydrocarbon chain binds to the maximum number of hydrogen atoms and all the carbons are linked by single bonds. Fats are made of glycerol and fatty acids. Triglycerides are the most common fats which involves three fatty acids linked to one glycerol molecule (Fraser, 2012).
Saturated and Unsaturated Fatty Acids
A Triglyceride Molecule
There are four types of fats in foods: polyunsaturated, monounsaturated, saturated and trans fats. Monounsaturated fats consisting of one double bond and polyunsaturated fats consisting of two or more double bonds are found primarily in vegetable oils. These unsaturated fats tend to lower the bad LDL cholesterol and are good fats. Vegetable oils are polyunsaturated, meaning that there are double bonds present. Omega-3 fatty acids are also a type of polyunsaturated fat. Researches have shown omega-3 to prevent and reduce the symptoms of depression, memory loss, and dementia. Omega-3 has also been shown to lower the risks of heart diseases, stroke and cancer. It may also reduce the symptoms of arthritis and skin inflammation and help support a healthy pregnancy (Smith, n.d., http://www.helpguide.org/life/healthy_diet_fats.htm). The following tables provide examples of healthy and unhealthy fats.
Good Fats
Monounsaturated fat
|
Polyunsaturated fat
|
Olive oil
Canola oil
Sunflower oil
Peanut oil
Sesame oil
Avocados
Olives
Nuts (almonds, peanuts, macadamia nuts, hazelnuts, pecans, cashews)
Peanut butter
|
Soybean oil
Corn oil
Safflower oil
Walnuts
Sunflower, sesame, and pumpkin seeds
Fatty fish (salmon, tuna, mackerel, herring, trout, sardines)
Soymilk
Tofu
|
Bad Fats
Trans fat
|
Saturated fat
|
Commercially-baked pastries, cookies, doughnuts, muffins, cakes, pizza dough
Packaged snack foods (crackers, popcorn, chips)
Stick margarine
Vegetable shortening
Fried foods (french fries, fried chicken, chicken nuggets, breaded fish)
Candy bars
|
High-fat meat (beef, lamb, pork)
Chicken with the skin
Whole-fat dairy products (milk and cream)
Butter
Cheese
Ice cream
Palm and coconut oil
|
Some trans fats are naturally occurring in some animal-based foods, but many are also formed by adding hydrogen to vegetable oil through the partial hydrogenation process which makes the oil into solid fats and more difficult to digest. Naturally occurring unsaturated fatty acids, which are normally found as the cis- isomer about the double bonds, altered by partial hydrogenation, will have the effect of straightening the chains by changing to trans double bonds. Still remaining unsaturated, the fatty acids of the same number of carbons, hydrogens, and oxygens as the original cis fatty acids is shaped in a more linear form as opposed to the bent form. The trans fatty acids are classified as saturated fats, which are solids due to their straight chains and can be packed together more closely. In contrast, the unsaturated fatty acids have bends in their structure and cannot be packed as tightly and stay more fluid (Elmhurst College, 2003, http://www.elmhurst.edu/~chm/vchembook/558hydrogenation.html; Fraser, 2012; Health Canada, 2009, http://www.hc-sc.gc.ca/fn-an/nutrition/gras-trans-fats/index-eng.php; Mayo Clinic, 2014, http://www.mayoclinic.org/diseases-conditions/high-blood-cholesterol/in-depth/trans-fat/art-20046114).
Cis- Isomer becomes Trans Isomer through Partial Hydrogenation
Many food manufacturers in the U.S. have already eliminated the use of trans fats. By 2012, 75 percent of the trans fats has been removed from the American food supply over the course of 10 years. The FDA’s new proposed banning of all artificial trans fats in processed foods claimed that the elimination could prevent 20,000 heart attacks and 7,000 heart-related deaths each year in the U.S. Michael Jacobson, executive director of the Centre for Science in the Public Interest, has been campaigning for decades to reduce the use of trans fat in processed foods. He is glad about the change and says in an interview with CBC that “if the FDA finalizes its tentative decision, most food companies would replace hydrogenated oil, the source of the trans fat, with a healthier oil” (CBC News, 2013, http://www.cbc.ca/news/business/u-s-trans-fats-ban-puts-pressure-on-health-canada-1.247235; Fraser, 2012).
A ban on trans fats has not yet been enacted in Canada. In 2006, there was a recommendation to Health Canada to end the use of trans fats. However, the Canadian government has not acted in response. Bill Jeffery, the national coordinator for the Centre for Science in the Public Interest, said that it's hard to say what the implications of the U.S. proposal will be for Canadians. "It may be that U.S. food manufacturers [who] export to Canada will just export a safer product with less trans fat in it, or maybe they will see Canada as a market to dump their foods and maybe we will end up with more trans fat coming across the border." Although the majority of the Canadian food supply is trans-fat-free due to voluntary reductions, a ban should still be imposed in order to prevent unnecessary risks and deaths each year. Governments should be more proactive and it is easy because there are substitutes (CBC News, 2013, http://www.cbc.ca/news/health/trans-fat-ban-proposal-in-u-s-may-affect-canadians-1.2418147; Fraser, 2012).
A gymnast and a weightlifter should not follow a general food guide that tells them the amount of fats they need to consume. A weightlifter would need to consume more healthy fats in a day to supply the body with enough calories for the intense workouts that they have. A gymnast will require less fats because they need to have controlled diets that would help maintain their figure for safety and aesthetic purposes. Both athletes will not succeed if they followed a general guide because their different bodies require different amounts of nutrients (Castle, 2014, http://www.fitday.com/fitness-articles/nutrition/carbs/simple-vs-complex-carbohydrates.html#b; Litt, 2004; Stark, 2014, http://www.fitday.com/fitness-articles/nutrition/carbs/simple-vs-complex-carbohydrates.html#b). Chapter four will talk more about the difference in the nutrient requirements for different types of athletes.
Micronutrients
Vitamins and Minerals
In addition, these nutrients also work to build strong and healthy bones. For example, dairy are a good source of calcium which help build stronger bones. Calcium cannot be absorbed without vitamin D, therefore, it is also important to consume foods that contain vitamin D. Vitamins can be water and fat soluble. Fat soluble vitamins like A, D, E, K, do not dissolve in water and are stored in the liver of the body. Excessive amounts, for example, obtained from vitamin supplements can be toxic. However, excessive intake of these nutrients is not an issue if these vitamins are obtained from natural foods. Water soluble vitamins such as C and B dissolve in water and cannot be stored in the body. Therefore, excessive amounts would be simply excreted from the body through urine (Litt, 2004).
Vitamins and minerals are micronutrients because they are required in small amounts. They are used by the body to process food into energy; in other words, they allow the body to use calories. Athletes require more of these micronutrients than nonathletes do because they consume more calories that need more of these micronutrients to process (Litt, 2004).
Water
Water is a vital nutrient for everyone. Adequate hydration is especially important for athletes as it can change how they feel and perform (Litt, 2004).
Conclusion
Everyone should consume all six types of nutrients as each serve an important role in the body. The total amount of each nutrient that should be taken could vary immensely from one person to another depending on one’s body mass and the sport that one plays.
