A Closer Look at The Components Of a Balanced Diet

Transcription

1 A Closer Look at The Components Of a Balanced Diet The essential nutrients are carbohydrates, fats, proteins, vitamins, minerals, dietary fibre and water. These nutrients will ensure that the systems and cells of the body function efficiently. They will provide the body with the energy required to perform, enable the body to grow and repair following training, as well as keep illness and disease at bay. Carbohydrates, fats and proteins are termed macronutrients and are the energy providers while vitamins and minerals are micronutrients which perform a range of metabolic functions within cells. Macronutrients: elements from your diet that provide energy including fats, carbohydrates and proteins. They are termed macronutrients because we need more than just a few grams of these daily. Micronutrients: elements from your diet that perform a range of metabolic functions within cells. They re termed micronutrients because we need these in relatively small quantities. 1. Outline the three types of macronutrient and explain the specific exercise-related function of each. Carbohydrates Carbohydrates can be divided into simple and complex forms. Simple carbohydrates Sugars and jams Sweets and confectionery Fruit Soft drinks Complex carbohydrates Potatoes Pasta Bread Nuts and pulses

2 Carbohydrates are stored in the muscles and liver as glycogen. The glycogen storage capacity of the body is about 350g in the muscles, 100g in the liver and approximately 5-10g in the blood as glucose. Once this capacity is exceeded, excess carbohydrates are readily converted to fat and stored as adipose tissue. This is particularly true of simple carbohydrates. Glycogen: the stored form of carbohydrate in the muscles and liver. Glucose: the sugar molecule which is broken down to release energy for exercise. Adipose tissue: fatty tissue stored beneath the skin and around some vital organs. 2. An athlete is eating lots of carbohydrates each day in order to fuel their body. They had hoped the exercise they were doing would help them to lose weight, however they are putting weight on. What advice would you give them to explain what may be happening and how they can avoid it? The glycaemic index (GI) is a measure of the effect different foods have on blood glucose levels. Pure glucose has a glycemic index of 100. Foods with a high GI provide a rapid surge in blood glucose levels, while those with a low GI release their energy more slowly. We might expect increases in blood glucose that accompany consumption of high GI foods to be useful in providing energy, but in fact they only give a relatively fleeting high and in the long run will be detrimental to performance. This is because, in order to maintain blood glucose levels within a healthy range, the pancreas releases insulin which carries the glucose out of the blood and into the cells. Excessive consumption of high GI foods results in an increased release of insulin which, in fact, causes blood glucose levels to fall rapidly. Although there is room for some foods with a high GI in everybody s diet, a large proportion of an athlete s carbohydrate intake should come from foods that have a low GI. These are converted into glucose at a much slower rate, so blood glucose levels are sustained over a much longer

3 period. Low GI foods have a GI of 55 or less. Medium GI foods have a GI of 56 to 69. High GI foods have a GI of 70 and above. The table below is drawn from data published in the American Journal of Clinical Nutrition - Issue 66, 1997

4 3. You must reflect on your own diet. Using the table on the previous page discuss whether your diet is suited to an endurance sporting event such as the Great North Run. Fats Fats are the major source of energy in the body at rest and during low-intensity exercise and are therefore essential for good health. There are three main types of fats. Saturated fats found in meats and dairy products (such as butter and cheese). These have no role in keeping the body healthy when eaten excessively. They can raise cholesterol levels and increase the risk of obesity and heart disease. Monounsaturated fats found in olive oil, avocados and some nuts such as peanuts. These fats can actually reduce cholesterol levels and therefore reduce the risk of heart disease. Polyunsaturated fats found in soya beans, sunflower and corn oils and some nuts and seeds. These can also help to reduce cholesterol and reduce the risk of heart disease

5 4. Which category of fats in the table on the previous page do you eat most of? How could you improve this? The Department of Health recommends a fat intake of no more than 32% of total calories (a maximum of 10% from saturated fats, 12% monounsaturated fats and a max of 10% from polyunsaturated fats). Furthermore a healthy diet should also include some foods rich in Omega 3 fatty acids (found in oily fish) and Omega 6 fatty acids ((in olive oil and sunflower oil). Trans fats and hydrogenated oils should be avoided at all costs as they can increase cholesterol levels and also increase the risk of obesity and heart disease. Fats in the body are stored as triglycerides in the adipose tissue and skeletal muscle. Energy from triglycerides is released through the oxidation of free fatty acids. This is a relatively slow process and can therefore only provide the body with its energy requirements at rest or during low to moderate intensities of exercise. Cholesterol: a fat-like substance that is essential for maintaining health but which cannot be made by the body, however high concentrations in the blood increase the risk of heart disease. Omega 3 and 6 fatty acids: fatty acids (found in fish oil and linseed oil, respectively) that are essential for maintaining health but cannot be made by the body. Hydrogenated oils and trans fats: oils that are hydrogenated are transformed from their normal liquid state into solids, to make margarine for instance. The unsaturated oil is converted to a saturated fat and its polyunsaturated benefits are removed. It is formed into a trans fat, these can be found in a wide array of processed foods including biscuits and other baked foods. An excess of trans fats in the blood stream is thought to raise cholesterol levels. Triglycerides: the form in which most fat is stored in the body. Oxidation: oxidation of saturated fat provides the body with the energy it needs to function. Free fatty acids (FFAs): the components of fat that are used by the body to provide energy when at rest or during low/moderate exercise.

6 5. Read the Mail Online article on trans fats. For HW, look at the foods in your cupboard at home. List those that contain trans fats, remember they may be labelled as hydrogenated oils. Are there alternatives that could be bought instead? Protein Protein is the third and final energy-providing macronutrient. A max of 10% of the energy released during exercise is derived from protein and it is only true when participating in endurance activities lasting more than an hour. Proteins also provide the amino acids required for the creation of all enzymes and some hormones. Protein provides the following functions for exercise: Proteins provide the amino acids required for the growth and repair of cells and tissues such as skeletal muscle Proteins provide the amino acids necessary for the manufacture of enzymes and hormones used in the production of energy Proteins provide the amino acids necessary for the manufacture of haemoglobin and myoglobin essential for oxygen transport Proteins can provide energy during endurance based activities. Amino acids: the main components of protein that ultimately contribute to the growth and repair of the body s tissues and promote recovery of the body following exercise. Haemoglobin: an iron based protein in the blood that transports oxygen and carbon dioxide to and from the muscle cells. Myoglobin: a protein in the muscle cells that stores and transports oxygen 6. Discuss the value of using protein supplements to enhance performance in both power-based and endurance based activity.