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Sport By Sport Diet Guide

Posted by: pshields on Tuesday, January 04, 2005 - 04:03 AM Print article Printer-friendly page  Email to a friend

Sport By Sport Diet Guide

Jane Pidcock MSc

Posted: December 26, 2004

Whatever Your Sport, Nutrition Should Be An Integral Part Of Your Training And Competition Strategy. Although The Emphasis Will Vary According To The Activity You're Involved In, There Is A Consensus Among Sports Scientists On Guidelines That Athletes Should Be Aiming For.

The International Conference on Foods, Nutrition and Sports in Lausanne (1991) agreed the following nutrient intakes to be optimum for most sports: 60-70% of calories in the diet from carbohydrates, 12% from protein and the remainder (18-28%) from fat. This in effect means eating a diet far higher in carbohydrate and lower in fat and protein than average.

Later in this article we will go on to consider detailed requirements for different types of sports activity. But first, we'll take a look at the three key ingredients in sports nutrition: carbohydrates, fluid and iron.

The carbohydrate connection Carbohydrate is a crucial fuel for exercise. The body makes its own carbohydrate store, known as glycogen, which is stashed away in the liver and muscles. Glycogen is the body's fuel of choice for any exercise more intense than a gentle jog. This is because it can be broken down to provide energy more quickly than fat (the body's other major energy store). However, the snag with glycogen is that only limited amounts of it can be stored. This means that regular training, as well as competition where activity is at least an hour long, carries the risk of glycogen depletion. Low glycogen stores will mean a more sluggish performance and an increased risk of injury.

Strategies to minimise this problem include carbohydrate loading (see box, and the following article), ensuring that a high-carbohydrate diet is eaten the whole time during training to avoid burnout; also, consuming carbohydrates during exercise (eg, a cycle ride) or between rounds (eg, a tennis tournament) can cut down on glycogen loss and keep performance boosted.

If you're in regular training, eating lots of carbohydrate-rich foods will encourage your body to store glycogen (see Table I for carbo contents of various foods). A guideline to aim for is 8-lOg carbohydrate per kg of body weight per day. For an average man (70kg), this would mean aiming for a daily intake of 560-700g; for an average woman (55kg), between 440-550g. Tips for boosting your carbo intake The twin strategies are to cut back on fat and to increase carbohydrates: 1 Base meals around carbohydrate foods - potatoes, pasta, rice, bread. 2 Eat smaller portions of fat-rich foods (eg meat, pies, cheese) and fill up with extra potatoes or bread. 3 Porridge made with water makes a high-carbohydrate start to the day. 4 Drink fruit juice with meals, and a milky drink at bedtime. 5 Cut bread extra-thick for sandwiches. 6 Try carbohydrate-rich snacks that are also low in fat: eg fresh or dried fruit, water biscuits spread with jam. 7 Choose pasta sauces based on tomatoes or vegetables rather than meat or cheese.

Timing your carbo intake If you need to replenish your glycogen stores quickly (eg you're training every one or two days) it's best to take advantage of the fact that the body is more likely to make glycogen immediately AFTER exercising - the sooner, the better. Some foods are better than others for this - the best are those with a high 'glycaemic index' (a term which means they will bring about a large surge in blood sugar). Examples of such foods are: bread (white or wholemeal), rice, potatoes, raisins, bananas, glucose, sucrose and honey. If you can't face eating straight after exercising, try a carbo-rich drink instead.

Fluid, the second key ingredient For many athletes, dehydration is something to watch out for. Even moderate fluid losses can mean operating at less than 80% of your potential, and more significant losses could be dangerous to your health.

To prevent this unhappy state of affairs, the answer is to drink. Water is perfectly adequate for most purposes. However, if you're exercising under particularly hot conditions, and/or you know that you are a champion sweater, you may want to consider one of the commercially formulated sports drinks. Isotonic and hypotonic sports drinks are designed to zap water into your bloodstream as fast as possible, and a number of studies have found that they have a slight edge over plain water. You can make up your own version of a sports drink by adding a pinch of salt and 2-4g glucose per lOOml of water.

To make sure that your fluid balance is well in the black before competing, drink more water than you usually would for the few days beforehand. Don't drink alcohol the night before an event - it will dehydrate you. Before competing, try to drink between 1/2 and 1/4 pint 15 minutes before the start. (For more on fluid replacement, see page 6.)

Iron, the third key ingredient Many athletes run the risk of low iron, partly because the stresses of their sport lead to increased losses of iron from the body (runners seem particularly susceptible). A number of studies have found that people in regular training and/or sports activity have low levels of ferritin, a body store of iron. People with low iron stores complain of tiredness and poor recovery from training. If the situation becomes worse, and haemoglobin (the form in which iron is transported around in the blood) levels fall, anaemia could result, with symptoms of severe fatigue, cramps, headaches and shortness of breath.

So what can you do if you suspect you're iron deficient? Iron supplements are available,and taking some for a few days to see if you notice any improvement could help identify if you really are deficient. However, supplements are commonly associated with side-effects such as nausea and heartburn, so your best bet is to try and boost your iron intake by dietary means. Even i-f you don't suffer immediate side-effects, you should seek medical advice before taking an iron supplement regularly, because it's also possible to suffer health problems from too much iron!

Haem iron foods: liver, liver pate, lean steak, chicken (dark meat), fish, oysters, salmon Non-haem iron foods: eggs, breakfast cereal (fortified), wholemeal bread, spinach (cooked), lentils/kidney beans (cooked), tofu, sultanas, dried apricots, almonds, cocoa. Haem iron is better absorbed by the body than nonhaem. However, absorption of non-haem iron is enhanced by vitamin C, so include some raw or lightly cooked vegetables with a meal, or drink fruit juice. Conversely, drinking tea or coffee will make the iron more difficult to absorb.

Tailoring nutrition for specific sports As a broad generalisation, sports can be divided into activities that are aerobic (eg endurance events), anaerobic (short, intense bursts of activity, eg sprinting), and those that are primarily related to strength (eg weightlifting, throwing). In fact, there will often be a combination of all three elements, but there is usually more emphasis on one of the three.

The endurance athlete's priority is to maximise glycogen stores by eating a high-carbohydrate diet both in training and before an event. Carbo loading is advisable, especially for an activity lasting longer than 90 minutes. Care should be taken to avoid dehydration, and this balanced against the possible benefits of taking in extra carbohydrate during the activity. Sports drinks containing maltodextrins enable delivery of some carbohydrate without compromising fluid uptake; on a cool day, however, it could be worth drinking something with a higher concentration of carbohydrate. This will slow down fluid absorption but will spare muscle glycogen. Eating during an endurance event tends to be problematic for runners, but seems to be well tolerated by cyclists.

Sports with an anaerobic content are also performed at their best with muscles well-primed with glycogen. A training diet high in carbohydrate will therefore be beneficial. Carbo loading is not really necessary, however. For anaerobic activities, lactic acid build-up in the muscles is a limiting factor. Some research has shown that sodium bicarbonate taken before events such as a rowing race, 400m swim or 800m run has a positive effect. Some individuals suffer gastrointestinal side-effects, however, so experiment first in training. More recently, creatine phosphate supplements have shown consistently positive effects on short-term, high-intensity exercise, but long-term effects aren't yet known about.

Athletes involved in heats or rounds need to ensure that they recover adequately between events. A sweet drink or carbohydrate-rich snack after exercising will pack the glycogen back into the muscles. Similarly, keep topped up with fluids - if rehydration time is at a premium (eg between squash matches) you'd do well to try an isotonic or hypotonic sports drink - and make sure you're well-hydrated at the start of the day.

The common folklore in strength sports is that a high-protein diet is required. The consensus of most sports scientists is that, although the protein needs of strength athletes are slightly higher than the general population, high levels of protein intake are not necessary. In fact, in the quest for protein, many strength athletes end up eating unhealthy high-fat diets. The key issue for bulking up is adequate energy intake alongside a training programme. A high-energy intake from nutritious food will also be high in protein, carbohydrate, vitamins and minerals.

Many studies of strength athletes have reported heavy use of dietary supplements. Favourites include amino acids - arginine and ornithine, for example, are marketed as boosting growth hormone release, mimicking the effect of steroids. There is no proof that the small amounts of amino acids provided by these supplements have any effect at all on growth hormone levels or body condition.

We will now look at some special considerations for swimmers, cyclists, runners, and those involved in power sports.

Swimming Optimum body fat for swimmers has become controversial of late. Traditionally, swimmers tend to have more body fat than their counterparts in other sports such as running or cycling. This has always been considered to be an advantage because of the added buoyancy factor. However, recent research has thrown doubt on this accepted wisdom. A study at the University of Georgia found that more fat is not necessarily an advantage. In trials, extra body fat was found to decrease V02max (maximal aerobic capacity). Swimmers trying to lose fat should follow a diet which restricts calories by cutting down on fatty foods. Some popular weight-loss diets advocate cutting down on starchy foods - this is never recommended for an active sportsperson.

Cycling The long miles and hours of training undertaken by competition cyclists call for a high-energy diet. A dietary study of elite cyclists estimated their average daily calorie intake at over 6000 calories ! It's not possible to consume this much at three meals a day, so constant 'grazing' over the day is advised. Take care that snack foods are high in carbohydrates rather than fat-rich.

Distance running A nutrition-related problem a lot of runners have to contend with is gastrointestinal discomfort - from nausea to trots while on the trot. This seems to be a treat reserved for the distance runner - endurance cyclists don't suffer. It's thought that the problems are caused by the repeated jolting of the gut while running. Some tips that runners have found helpful are: 1 Try liquid food only for the last meal before a long run or pre-competition 2 Take care not to become dehydrated while running. Research has found that runners who take on board adequate fluid while running are less likely to suffer from gut problems 3 Avoid food high in fat or protein before your training runs, as research shows that these are more likely to induce nausea if eaten before exercise 4 Some athletes find that decreasing the fibre content of their diet before competing improves things.

Power sports A brief word about making weight (eg in combat sports, rowing, gymnastics). Drastic strategies such as sweating it out in a sauna, or using diuretics or laxatives, may cause an effective loss of body weight, but your body will have lost water, muscle and glycogen in order to achieve it. This will seriously handicap your performance, and it will be impossible to make good the deficit in the time between weighing-in and competing. The maximum weight loss that can be achieved without affecting fluid and glycogen stores is about 2lb a week. So ideally, you should be very close to your competition weight two to four days before competing. Female athletes: special considerations The two nutritional issues of particular relevance to female athletes are: first, avoiding anemia, and second, achieving a sensible weight. The daily iron requirement for menstruating women is higher than that for men. There is also a greater likelihood that women athletes will be vegetarian. Although there are vegetarian sources of iron, care must be taken to eat enough of them, and in a context that will enable them to be absorbed well (see section on iron, above).

Females achieving a very low level of body fat can end up with their periods becoming irregular, or even stopping altogether. This carries potential health risks, as studies have shown that female athletes whose periods have stopped have lower levels of minerals (including calcium) in their bones - meaning a higher risk of osteoporosis and stress fracture. Any female athlete with abnormal menstruation should consult her GP, and may need to consider gaining weight. In addition, calcium-rich foods should be consumed, such as dairy products, nuts and seeds, dried fruit and green vegetables.


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