Your digestive system converts the carbohydrates in food into glucose, a form of sugar carried in the blood and transported to cells for energy. The glucose, in turn, is broken down into carbon dioxide and water. Any glucose not used by the cells is converted into glycogen - another form of carbohydrate that is stored in the muscles and liver. However, the body's glycogen capacity is limited to about 350 grams; once this maximum has been reached, any excess glucose is quickly converted into fat. Base your main meal with the bulk on the your plate filled with carbohydrates and small amounts of protein such as meat, poultry and fish. The extra protein & vitamins you need will be in the starchy carbohydrates.
Lactose Intolerance
Lactose intolerance is when the mucosal cells of the small intestine fail to produce lactase which is essential for the digestion of lactose. Symptoms include diarrhea, bloating, and abdominal cramps following consumption of milk or dairy products.
Carbohydrates for Performance
Following training & competition an athlete's glycogen stores are depleted. In order to replenish them the athlete needs to consider the speed at which carbohydrate is converted into blood glucose and transported to the muscles. The rapid replenishment of glycogen stores is important for the track athlete who has a number of races in a meeting. The rise in blood glucose levels is indicated by a foods and the faster and higher the blood glucose rises the higher the GI. Studies have shown that consuming high GI carbohydrates (approximately 1grm per kg body) within 2 hours after exercise speeds up the replenishment of glycogen stores and therefore speeds up recovery time. There are times when it is beneficial to consume lower GI carbohydrates which are absorbed slowly over a longer period of time (2-4 hours before exercise). Eating 5-6 meals or snacks a day will help maximise glycogen stores and energy levels, minimise fat storage and stabilise blood glucose and insulin levels.
Eating and Competition
What you eat on a day-to-day basis is extremely important for training. Your diet will affect how fast and how well you progress, and how soon you reach competitive standard. The page on provides some general nutritional advice to help you manage your weight and .
Once you are ready to compete, you will have a new concern: your competition diet. Is it important? What should you eat before your competition? When is the best time to eat? How much should you eat? Should you be eating during the event? And what can you eat between heats or matches? A lot of research has been done in this area, and it is clear that certain .
What do I need to do ?
Calculate your daily basic and extra requirements, monitor your daily intake (especially your carbohydrates) and then adjust your diet to meet your daily requirements. A good balanced diet should provide you with the required nutrients but does needs to be monitored. The simplest way to monitor the 'energy balance' is to keep a regular check of .
Key factors in your training diet
Each day have three main meals and two to three snacks. All meals should contain both carbohydrate and protein - 20 to 30 grams worth of protein with each main meal and 10 to 20 grams with each snack.
The amount of carbohydrate will vary greatly, mainly depending on the your workload. It may be in the region of 40 to 60 grams for main meals and 20 to 30 grams for snacks. If you training hard and possibly doing multiple daily sessions, the recovery meal is critical. Have 1grm of carbohydrate per kg of body weight and about 30 grams of protein. Have a drink (eg a recovery drink or a pint of skimmed milk) and a banana immediately post-training (this provides about 10 grams of protein and 30 grams of carbohydrate) followed within about 45 minutes with more substantial food such as beans on toast and tuna.
Always try to eat at least five pieces of fruit per day. Skimmed milk is a great protein food and provides critical minerals, such as calcium and phosphorous.
Food Composition Tables
are widely used to assess nutrient and energy intakes, and to plan meals. The composition of food can vary widely, depending, among other factors, on the variety of plant or animal, on growing and feeding conditions and, for some foods, on freshness. Tables are based on average values from a number of samples analysed in the laboratory and therefore only provide a rough guide.
Vitamins
Vitamins serve crucial functions in almost all bodily processes (immune, hormonal and nervous systems) and must be obtained from food or supplements as our bodies are unable to make vitamins.
There are thirteen vitamins classified as either water soluble (C and B complex) or fat soluble (A, D, E and K).
Fat Soluble Vitamins
Fat-soluble vitamins are absorbed, together with fat from the intestine, into the circulation. Any disease or disorder that affects the absorption of fat, such as coeliac disease, could lead to a deficiency of these vitamins. Once absorbed into the circulation these vitamins are carried to the liver where they are stored.
Vitamins A, D, E and K make up the fat soluble vitamins. Vitamins A, D and K are stored in the liver and vitamin E is distributed throughout the body's fatty tissues.
Water Soluble Vitamins
Water-soluble vitamins, such as Vitamin C and the B vitamins are stored in the body for only a brief period of time and are then excreted by the kidneys. The one exception to this is vitamin B12, which is stored in the liver. Water-soluble vitamins need to be taken daily.
Vitamin C (ascorbic acid) and the B complex group make up the nine water soluble vitamins. The B complex group comprises of vitamins:
- B6 (pyridoxine)
- B1 (thiamine)
- B2 (riboflavin)
- B12 (niacin, pantothenic acid, biotin, folic acid and cobalamin)
Vitamin sources, uses and deficiency problems
Vitamin A (fat-soluble)
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Sources: Dairy products, eggs, liver. Can be converted by the body from the beta-carotene found in green vegetables, carrots and liver.
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Uses: Maintains the health of the epithelium and acts on the retina's dark adaptation mechanism.
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Deficiency leads to: Keratinisation of the nasal and respiratory passage epithelium, night blindness
Vitamin B1 (thiamine) (water-soluble)
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Sources: Yeast, egg yolk, liver, wheat germ, nuts, red meat and cereals
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Uses: Carbohydrate metabolism
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Deficiency leads to: Fatigue, irritability, loss of appetite; severe deficiency can lead to beri-beri
Vitamin B2 (riboflavin) (water-soluble)
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Sources: Dairy products, liver, vegetables, eggs, cereals, fruit, yeast
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Uses: Intracellular metabolism
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Deficiency leads to: Painful tongue and fissures to the corners of the mouth, chapped lips
Vitamin B12 (water-soluble)
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Sources: Liver, red meat, dairy products and fish
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Uses: Essential for manufacturing of genetic material in cells. Involved in the production of erythrocytes
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Deficiency leads to: pernicious anaemia
Vitamin C (ascorbic acid) (water-soluble)
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Sources: Green vegetables and fruit
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Uses: Essential for the maintenance of bones, teeth and gums, ligaments and blood vessels. It is also necessary for ensuring a normal immune response to infection
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Deficiency leads to: Scurvy
Vitamin D (fat-soluble)
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Sources: Fish liver oils, dairy produce. Vitamin D is formed in the skin when it is exposed to sunlight
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Uses: Has a role in the absorption of calcium, which is essential for the maintenance of healthy bones
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Deficiency leads to: Rickets
Vitamin E (fat-soluble)
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Sources: Pure vegetable oils; wheat germ, wholemeal bread and cereals, egg yoke, nuts sunflower seeds
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Uses: Protects tissues against damage; promotes normal growth and development; helps in normal red blood cell formation
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Deficiency leads to: May cause muscular dystrophy
Vitamin K (fat-soluble)
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Sources: Green vegetables
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Uses: Used by the liver for the formation of prothrombin
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Deficiency leads to: Bleeding due to delayed clotting times caused by lack of clotting factors. Patients may show signs of bruising easily and have nosebleeds.
Daily Requirements
Vitamins contain no useful energy for the body but they do link and regulate the sequence of metabolic reactions that release energy within the food we consume. Vitamins cannot be made in the body and must be obtained in our diet A well balanced diet provides an adequate quantity of all vitamins regardless of age and level of physical activity.
The recommended daily requirements (RDR or RDA) for men, women are shown in the Table below. These requirements should be easily met if a balanced diet is adhered to; however, there are groups that may be at greater risk of developing vitamin deficiencies than others. These include those on restricted diets, patients who have digestive disorders that affect the absorption of fat, patients on lipid-lowering medication and those whose dietary choices are affected by financial or for conscientious reasons (Trounce and Gould, 1997). For these groups there may be advantages in taking a general or specific vitamin supplement following advice from a doctor or nutritionist. However, for those on a balanced diet there is little to be gained from taking additional vitamins (NHS Direct Online, 2003).
Toxicity of Vitamins
Fat soluble vitamins should not be consumed in excess as they are stored in the body and an excess can result in side effects. An excess of vitamin A may result in irritability, weight loss, dry itchy skin in children and nausea, headache, diarrhea in adults.
An excess of water soluble vitamins should not result in any side effects as they will disperse in the body fluids and voided in the urine.
Free Radicals
Electron leakage in the electron transport system results in approximately 2 to 5% of oxygen containing free radicals like superoxide, hydrogen peroxide and hydroxyl. The body's level of pentane can be used to monitor the amount of free radicals.
Exercise increases the production of free radicals and a build up of free radicals increases the potential for cellular damage to many biological substances. Research indicates that the body's natural defences of a well nourished athlete are adequate in response to increased amounts of free radicals.
Available research indicates that if supplements can be beneficial in combating free radicals then vitamin E may be the most effective.
Vitamin and mineral interactions
Many vitamins and minerals interact, working alongside each other in groups e.g. a good balance of vitamin D, calcium, phosphorus, magnesium, zinc, fluoride, chloride, manganese, copper and sulphur is required for healthy bones.
Many of them can enhance or impair another vitamin or mineral's absorption and functioning e.g. an excessive amount of iron can cause a deficiency in zinc.
Effects of a bad diet
Cholesterol
Cholesterol is a type of fat (or lipid) present in certain foods and made by your liver. A certain amount is essential for the formation of cell membranes (the basic building blocks of life).
Too much "bad" (LDL = low density lipoprotein) cholesterol causes damage (atherosclerosis) to your artery walls. This build up of cholesterol results in narrowing of the arteries (which transport blood pumped from heart around the body). This process happens slowly over many years in most people in Western countries.
Lack of blood supply due to narrowed arteries can affect the heart (causing angina), the legs (causing claudication) and brain (causing transient ischaemic attacks, "TIAs"). If the artery blocks off completely it can cause a heart attack or stroke.
Some of the adverse affects of LDL cholesterol are reduced by "good" (HDL) cholesterol, which removes LDL cholesterol from the artery walls.
Most people can reduce their cholesterol levels 10-20 percent by careful eating. However, this may not be enough in many cases to reduce risk and medication may be required. Increasingly, well conducted research is showing benefits from drug treatment in high risk groups.
Dietary changes:
- Reducing your cholesterol by 0.6 mmol/l long-term will reduce your risk of a heart attack by one third. This means reducing the amount of saturated fat eaten (mainly found in red meat and dairy products). Plant foods such as fruits, vegetables, grains, rice and potatoes contain no cholesterol or saturated fat, which leads to increased cholesterol levels.
- The actual cholesterol in food is not as harmful as saturated fat in the diet. Most cholesterol in the body is made in your own liver using saturated fat from the diet.
- Saturated fats are found mainly in animal foods such as meat and full fat dairy products. Two vegetable oils, coconut and palm oil are also high in saturated fat. They are used in commercially baked cakes and biscuits. Saturated fats are bad because they increase LDL cholesterol and lower HDL cholesterol.
- Polyunsaturated fats are good because they lower LDL cholesterol (although they may also reduce HDL cholesterol). Polyunsaturated fats are in sunflower, safflower, corn, soybean, nuts and fish. Omega-3 polyunsaturated oils, found in some fish and building blocks are found in some foods. Omega-3's are particularly effective in preventing heart disease, even though they do not alter cholesterol levels much.
- Monounsaturated fats are found particularly in olive, canola, peanut and sunflower oils, avocados, olives, nuts and sesame seeds. Monounsaturated fats are good because they decrease LDL cholesterol without much effect on HDL cholesterol. Their consumption may be responsible for the lower incidence of heart disease in Mediterranean countries.
- A healthy diet includes lots of fruit, vegetables, whole grain bread, cereals, legumes (peas, beans and lentils). Eat fish at least twice weekly, especially those high in Omegat-3. Eat small amounts of only lean meat (fat removed), poultry without skin, and low-fat dairy products. Eat no more than three eggs each week. Use as little fat and oil as possible - grill, boil, steam, bake or microwave rather than fry. Use monounsaturated margarine or oil rather than butter for thin spreading and cooking. Avoid prepared foods - they contain too much fat.
- Coffee that is unfiltered (i.e. espresso, plunger or boiled) will raise levels of bad LDL cholesterol. Therefore, it is best to choose filtered, percolated or instant coffee and limit intake to no more than five cups each day.
- Recently, some compounds derived from plants ("plant sterols") have been found to lower the bad LDL cholesterol by a further 10-15 percent, over and above what can be achieved by regular dieting alone. These compounds have been incorporated into margarines which are now available in New Zealand as Flora Pro-Activ and Logicol.
- A modest intake of alcohol may be healthy by increasing HDL cholesterol and reducing the risk of heart attacks. Alcohol intake should be limited to two standard drinks daily for women and three standard drinks daily for men (see table at bottom for standard drink definitions). Red win contains antioxidants that may increase its beneficial effect.
Diabetes
Type 1
About 10-15% of people with diabetes will have what is called Type 1 diabetes (insulin-dependent diabetes). These people have a significant deficiency in the production of insulin. What causes that is unclear, but it appears that there is a gene that predisposes the insulin-producing cells (B cells) in the pancreas to be destroyed by the immune system. Type 1 diabetes can occur at any age, not just in children. It can take many years to deplete the pancreas' stores of insulin and blood tests can test for antibodies that indicate that the destructive process is or has occurred. Because of a significant deficiency of insulin, almost all of the people with Type 1 diabetes will need to take insulin injections at or soon after the diagnosis.
Type 2
By contrast, Type 2 diabetes which makes up the bulk of people with diabetes, usually occurs in adults, although in countries where there is an increasing prevalence of obesity and diabetes, it is occurring in teenagers and even some children. It is characterised by both a deficiency in the production of insulin and also in the action of insulin (so called insulin resistance). It is more common in certain races and is becoming increasingly more prevalent in the world. It is estimated that the world-wide diabetes population will soon reach 200 million and it seems to be growing in parallel with an increasing prevalence of obesity and a sedentary lifestyle. One of the biggest explosions of diabetes may be occurring around the Pacific rim and Asia. The causes of Type 2 diabetes are not known but a number of gene defects have been noted. This type of diabetes runs more closely in families. Obesity occurs in 75-80% of patients and the disorder is often closely linked with high blood pressure and high lipid (cholesterol and triglyceride) levels and premature heart disease.
