Dieticians recommend that the average person’s diet should be made up of about 47% carbohydrates, with the majority of these coming from starchy foods (complex CHOs). However, an athlete should increase the amount of calories coming from carbohydrates in their diet to about 55-65% according to some sport nutrition experts. Having this much in their diet allows them to have large storages of glycogen which allows them to exercise at their optimum level and meet the muscles energy requirements. Energy requirements are dependant upon the sport the athlete is participating in. For example, short-burst, high intensity sports such as sprinting, jumping and pole vaulting only use 100% carbohydrates as their main energy source. For longer events such as, long distance, the body uses carbohydrates and fats are used as fuel sources. (B)
During endurance events such as the marathon it is important to keep glucose levels high as that the athlete does not become fatigued. In order to do this it is recommended that every hour that they are exercising they should be receiving 50 – 60g of carbohydrates. However, instead of using starchy CHOs, sugary ones will also do the trick, as they are faster releasing and can be given in the form a fruit drink. This is why during the London marathon there are regular intervals of drink stations where the runners can grab a drink usually made up of one part fruit juice to one part water. (B)
Fats
Fats are also another source of energy; these however, release energy much slower than carbohydrates. We tend to use fat as a reserve energy store after burning all of our carbohydrates. Fat also helps our body in other ways such as protecting our vital organs, regulating our body temperature and keeping our skin in a good condition. The majority of fat sources in foods come from things such as, butters, creams, vegetable oils, nuts and flesh of animals.
During exercise our main energy source is carbohydrates, however when resting and sleeping we use fats instead, these need a lot of oxygen to provide energy required. (C)
There are two components in a fat one being a glycerol and the other being a fatty acid. The most common lipid, a triglyceride, in nature looks like this,
It is made up of a glycerol which has the formula, C3H8O3 and 3 fatty acids. As previously discussed in carbohydrates, for the 3 fatty acids to attach to the glycerol a condensation reaction needs to occur.
Therefore in the formation of a triglyceride, (as shown above), a reaction must happen between the 3 hydrogen molecules in the glycerol and the OH molecule in each of the 3 fatty acids. As a result of this condensation reaction 3 water molecules are formed and the 3 oxygen molecules in the glycerol bond with the carbon molecule at the end of each of the 3 fatty acid tails.
Fatty acids are the building blocks for fat, they are either saturated, monounsaturated or polyunsaturated. (C)
Saturated Fatty Acids
Saturated Fatty Acid – Within the chain that makes up the fatty acid there is no carbon to carbon double bond. A good example of saturated is animal fat where it is solid at room temperature. The diagram below shows a saturated fatty acid.
H H H H H H H H H OH
- | | | | | | | | | |
- H-C-C-C-C-C-C-C-C-C-C=0
- | | | | | | | | |
H H H H H H H H H
Saturated fatty acids always form straight chains therefore they can be packed together very tightly; this allows humans to store chemical energy very compactly.
Saturated fats have been linked to the reason for high cholesterol and coronary heart disease. (C)
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Saturated fats are turned into cholesterol in the liver, in order to keep healthy we do need some of it, however if we include too much in our diet then too much is produced. As a result of too much cholesterol our arteries can narrow as fatty deposits are left there and this increases our blood cholesterol level; if this increase continues then a blockage may occur in a vessel resulting in a heart attack. (C)
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It is recommended that we should consume no more than 7% of calories in saturated fat in our daily diet. If we include any more this is when the problems with cholesterol can start to occur. (C)
Monounsaturated Fatty Acids
Monounsaturated fatty acids have only one carbon to carbon double bond in their chain with all the others just single carbon bonds. They are most commonly found in natural foods such as, avocados, nuts, olives and olive oil.
Unlike saturated fatty acids, monounsaturated fatty acids are actually good for us as they help lower blood cholesterol; therefore it is better to include these in our diet in place of saturated fats.
Monounsaturated fats tend to be branched unlike saturated fats which form a straight chain. This is a result of monounsaturated fats having a carbon double bond. (C)
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Polyunsaturated Fatty Acids
These fatty acids are also proven to help lower blood cholesterol; polyunsaturated fats tend to help get rid of it when it is newly formed which helps keep the level down and remove the fatty deposits left on artery walls.
Polyunsaturated fatty acids are very similar to monounsaturated fatty acids however; when they are polyunsaturated they have more than one carbon to carbon double bond. They also tend to be branched and liquid at room temperature and only tend to solidify when reaching temperatures similar to that of a refrigerator. (C)
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Polyunsaturated fats can be found in numerous food oils, mostly vegetable, such as safflower, sunflower, soybean, corn and cottonseed. These fatty acids can one of two types, either Omega-3 or Omega-6. Omega-3 fatty acids are most commonly found in cold water fish such as, salmon, mackerel, tuna, sardines and lake trout. Omega-3 is particularly good for us as it helps prevents heart disease as it lowers the amount of triglycerides and reduces blood clotting. (C)
Polyunsaturated fats are very important to our bodies as they supply us with essential fatty acids, (EFAs), which our bodies cannot synthesise so there is a need to get them from the foods we eat. EFAs are necessary for a range of functions within our bodies, especially in children as they help with growth and development and it keeps their skin healthy. The brain and the nervous system also rely a lot of EFAs as they also produce hormone-like substances that help regulate our body’s blood pressure; additionally they help prevent blood clotting and help the immune system. (C)
It is very important that an athlete includes fat in their diet; this is because after about 20 minutes of intense aerobic training, our carbohydrate reserve starts to deplete, when this happens we start using our fat store which acts as an almost endless supply of fuel, (energy). Aerobic training increases the body’s ability to use fat as fuel rather than use up all of our glycogen stores. The amount of fat an athlete stores or requires in their body depends upon the sport that they compete in and their natural body physique. Trained athletes can use fat as energy much more quickly than an untrained one; however when they start to use fat as fuel depends upon the duration of the event and the condition that the athlete is in. It is believed that fat can contribute up to 75% of the energy in demand during a pro-longed aerobic workout. Both athletes and all individuals should consume no more than 30% of calories from fat a day, with less than 10% of this coming from saturated fats. This tends to mean that a woman’s recommended daily allowance, RDA, of fat should be about 76g and a man’s should be about 100g. (D)
Proteins
Protein is an essential nutrient within our diet; it is needed for a number of functions the main one being growth and repair of muscles and tissues. It is also used for other purposes including:
- Structural integrity of cells and growth of the body.
- Formation of enzymes, digestive juices, haemoglobin and hormones.
- Protection of the body against infection.
- Help transport oxygen, nutrients and drugs.
- Production of milk proteins during lactation.
- To replace daily loss of proteins.
- Some proteins are enzymes and are used as catalysts.
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A source of energy, however the body prefers to use carbohydrates and fats. (E)
Sources of protein can be found in either plants or animals:
Proteins are very complex substances and are made of thousands of small units called amino acids. Amino acids are needed by almost every part of the body such as bones, muscles and organs. Within the human body there are about 21 amino acids of which some can be synthesised, however as a few cannot we have to supplement them in our food instead. Proteins contain the elements, Carbon, Hydrogen, Oxygen and Nitrogen, they can also include sulphur and sometimes phosphorous. The number of proteins we have is infinite and within the human body we have over 10,000. We need these proteins as they make us different to other species as proteins are the basis for determining our characteristics, DNA. (E)
There are over 100 amino acids of which 20 are commonly found in protein. Every amino acid contains a basic group, NH2, and a carboxyl group, COOH; if an amino acid contains one of each then it is neutral. Some amino acids have more of one group than the other;
- More basic groups = Basic amino acid
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More Carboxyl groups = Acidic amino acids
This diagram shows a neutral amino acid as it has one of each of the groups. The diagram below shows acidic amino acids, you can clearly see this as they both have 2 carboxyl groups and only one basic group.
It is easy to see in the next diagram that it is a basic amino acid as it has sufficiently more basic groups than carboxyl ones.
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Proteins can be joined together to form different structures. If two proteins are joined together by a condensation reaction, between the amino group of one acid and the carboxyl group of another, then a dipeptide is formed. If there is further extension of a protein chain then it is called a polypeptide. The bonds formed between these amino acids are known as peptide bond which is between CH – NH. A peptide bond can be broken by hydrolysis.
The three different structures involved with proteins are known as, primary, secondary and tertiary. (E)
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Primary Structure- These are straight chains and the most common way to indicate a primary structure is to write out an amino acid sequence. (E)
E.g. gly-gly-ser-ala
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Secondary Structure – This is when the peptide forms distinctive structures by local folding, including alpha helices and beta- pleated sheets. (E)
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Tertiary Structure – This is when the secondary structure folds again into a 3 dimensional structure. It is held in this position by hydrogen bonding. (E)
As a result of protein malnutrition the body can suffer, there are two main diseases associated with protein deficiency.
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Marasmus – This can result in an 80% weight loss below their recommended weight for their height. There are many symptoms and signs for Marasmus, dry skin, skin folds, drastic weight loss and severly hungry. As a result of this disease there can be life threatening infections, dehydration and a circulatory disorders, of which all need to be treated individually as well as the actual malnutrition. (E)
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Kwashiorkor – This is also a result of protein malnutrition. Early symptoms of this disease are fatigue, irratibility and lethargy. If protein depreivation is extended over a long period of time then other symptoms can occur including, growth failure, myuscle mass decreases, edema (swelling) and a low immune system. (E) 18th October 2006
For everyone nutritionists recommend that we consume only 10 – 12% of calories through protein. An athlete however, should relate the amount of protein intake to their weight and what event they compete in, therefore they should eat about 1 – 1.5 grams of protein per Kg of their body weight per day. It is not to be believed that excess protein in the diet will increase muscle bulk, it is strength and exercise which will do this. Therefore it is not necessary to consume protein supplements from health stores.
It is extremely important for athletes to contain protein in their diet; this is because it is not only needed for muscle growth but the repairs of muscle tissue which is broken down during intense exercise. It is known generally, that the greater the power-to-weight ratio then the faster he or she can move. As all force and power comes from our muscles it is important that they are kept at their maximum strength and mass, protein in the diet will help maintain this through growth and repair. Although this is more imperative for power athletes rather than endurance athletes, it is still vital that they can maintain muscles mass so they are not at risk of injury due to loss of power.
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Water
Water is the most important nutrient of them all; it is involved in every bodily function and makes up 70 – 75% of your total body weight. A single water molecule is made up of 2 hydrogen molecules and one oxygen molecule, known as H2O.
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It has many functions within the body such as;
- Maintaining your body’s temperature.
- Metabolize body fats.
- Helps with digestion.
- Lubricates and cushions organs.
- Transports nutrients.
- Flushes toxins from the body.
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We lose water through sweating and urine, the water lost due to this must be replaced by what we consume in our diets. If we do not drink enough water our bodies will become dehydrated and this can cause headaches, tiredness and lack in concentration. This is extremely important for athletes as they need to perform at their best when competing. For example, if a footballer became dehydrated he will not be able to play to his full potential and be aware of what was going on around him so; shots passes and tackles may be sloppy as he cannot concentrate properly.
We can get water from three different sources within our diet,
- Pure water or from other drinks such as squash and juices.
- Solid foods including all fruits and vegetables.
- As by products from chemicals reactions which occur within our body.
It is imperative that we drink the right amount of water everyday so our bodies are correctly hydrated. The British Dietetic Association recommends that,
…’the average adult should consume 2.5 litres of water per day,
at least 1.8 litres should come directly from beverages.’
This does not include when we have been exercising or when it has been a particularly hot day, therefore if in either of these situations we should increase the amount of water consumed in a day considerably.
18th October 2006 (information on water)
18th October 2006 (picture)
Water consumption is extremely important to everyone however, it is particularly vital for athletes to make sure they stay hydrated. Inadequate water intake can harmful to our bodies, as if we lose say 2% of water through sweat then this can lead to our blood level dropping resulting with the heart working harder. Athletes must ensure that they pre and re-hydrate as it improves their cardiovascular health, prevents muscle pain and delay and increases performance.
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During any event it is important that athletes keep themselves hydrated so should drink at intervals possible, it is helpful for them to drink chilled water as it is absorbed faster and lowers the body temperature. This table below shows an example of recommendations of hydration.
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There are other nutrients we need in the body these include;
- Minerals – There are a number of minerals which help with different parts of the body. The table below shows a list of the minerals we need within our diet and what they do for our bodies.
The four most commonly known minerals which are extremely important in our diet can be found in numerous foods.
- Calcium can be found in foods such as, dairy products (cheese, milk, and butter), leafy green vegetables and calcium fortified foods such as orange juice and cereals.
- Iron can be found in, meats (especially red meats e.g. beef), tuna, salmon, eggs, beans, dried fruits, leafy vegetables and whole/enriched foods such as wheat or oats.
- Potassium can be found in food such as, bananas, broccoli, tomatoes, citrus fruits, beans, lentils and dried fruits.
- Zinc can be found mainly in, beef, pork, lamb, lentils, beans, and peanuts.
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- Vitamins – Every single vitamin we consume has a special requirement within the body, like with minerals they are found in a variety of foods. Some of the most common vitamins which you will have probably heard of are, Vitamin D – required to keep bones healthy, Vitamin A – required to protect the surface linings of the eyes and respiratory tracts, Vitamin E – a powerful antioxidant and can help with keeping diseases away and certain cancers, Vitamin C – is used for a number of functions including healing of any cuts, strengthening bones and teeth and building resistance to infections.
Different vitamins can be found from different sources some of the most common ones are;
- Vitamin A – eggs, liver, fortified cereals, orange and green vegetables, apricots, peaches, mangos and many more.
- Vitamin C – red berries, tomatoes, broccoli, spinach, juices such as grapefruit and orange, kiwifruit and red and green peppers.
- Vitamin D – Manufactured by our bodies when sunlight gets on our skin. However can also be found in foods such as, egg yolks, fish oils and fortified foods like milk.
- Vitamin E – Vegetable oils, nuts, leafy green vegetables and whole grains.
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- Fiber – This is a nutrient that our bodies cannot digest however, they are very important in helping us remove food quickly from our bodies by keeping the colon smooth. Fiber can be found in many foods including, fruits, vegetables, dry beans and peas, nuts, seeds, breads and cereals.
Google – definition of Fiber. 18th October 2006