The body uses food to produce energy, to build, maintain and repair the muscles and other tissues and replace vital chemicals as they are used or lost. Basically, we split ‘food’ into five major components: 1Protein 2Fats 3Carbohydrates 4Vitamins 5Minerals
Amino Acids and Protein
Proteins are long chains of chemicals called amino acids. When we eat meat and nitrogen-rich vegetables, the proteins are broken down into these amino acids in the stomach and intestine. They then pass into the bloodstream where they are ready to be re-synthesised into our own body proteins. Proteins can be composed of as few as 50 amino acids or as many as several hundred amino acids.
There are 25 different amino acids available in our diets. Of these, 15 can be synthesised from other amino acids and these are called the non-essential amino acids. A further ten amino acids cannot be synthesised by our bodies; they must be obtained from the food we eat.
Non-Essential Amino AcidsEssential Amino Acids
Glutamine and Glutamic AcidLysine
Cysteine and CystineMethionine
Essential Amino Acids
Non-Essential Amino Acids
Asparagine and Aspartic Acid
The World Health Organisation recommends a daily intake of protein of at least 0.8 grams per kilogram (0.013 oz per lb) of body weight. This would mean that a man or woman weighing about 80 kg (176 lb) needs 64 g (2.3 oz) of protein each day. Athletes and very active people need a lot more.
The British Department of Health recommends that men in the 18-34 age range should consume 1.2 g of protein per kg (0.019 oz per lb) of body weight each day; women in the same age range should eat 1 g of protein per kg (0.016 oz per lb) of body weight. This means that an 80-kg (176-lb) man needs approximately 96 g (3.3 oz) of protein each day. This could be provided by about 450 g (1 lb) of best steak. Of course, the protein in our diet comes from a much wider range of different types of food than just meat. Proteins are also found in fish, eggs, dairy products and a wide range of vegetables, particularly cereals and legumes such as beans.
The vegetarian therefore faces little difficulty in getting his or her daily requirement of protein and, more particularly, his or her essential amino acids. The vegan faces a more difficult problem and must plan his or her diet much more carefully. The problem faced by the vegan is that protein from any one particular vegetable may be deficient in one or more of the essential amino acids. Fortunately, however, not all plants are deficient in the same essential amino acids. Consequently, in order to meet their daily requirements of the essential amino acids, vegans must eat a large range of vegetables, cereals and green-leaved plants. It is commonly believed that athletes, sportsmen and those undergoing hard physical training benefit from high-protein diets. After all, it is reasoned, these people want to build muscle and muscles are composed of protein. However, doctors are now arguing against the high-protein diet of steak and eggs. We should already obtain sufficient protein and the essential amino acids from a well-balanced diet that contains not only protein but all the other essential components such as sugars, fats, minerals and vitamins.
Red meat also contains a lot of saturated fat which is one of the most important factors in heart disease. In addition, fat is a poor energy source for the sportsman/woman or athlete.
The diet recommended for the professional athlete is rich in complex sugars (carbohydrates) and adequate in protein. High-protein diets are usually poor in energy-producing sugars. This means that the vital supplies of glycogen (the complex sugar in our muscles) are not present to fuel high-intensity training. In addition, excess protein is simply eliminated by the body and this elimination requires extra water. During training, a person on a high-protein diet may become seriously dehydrated.
High-protein diets aside, recent research work has shown that athletes, and those doing heavy physical work or training, may benefit from additional supplements of certain amino acids. These include both essential and non-essential amino acids. They include glycine, aspartic acid/asparagine, arginine, glutamine, serine, taurine, methionine, valine, leucine, isoleucine and cysteine.
Some of these amino acids give rise to other amino acids. For example, methionine is converted to both cysteine and taurine; taurine is important in wound-healing. The essential branched-chain amino acids such as valine, leucine and isoleucine promote muscle growth after intense training.
Cysteine, glycine, arginine and glutamine are involved with the maintenance of sugar in the blood. Asparagine/aspartic acid increases endurance in athletes. Your doctor can advise on supplements of these amino acids -some are contra-indicated in certain illnesses – and the recommended dose rate. They are usually supplied in powder form and it is usually recommended that they be taken after a meal. Some are best taken after consuming a high-carbohydrate meal.
At present, the medical advice concerning our daily protein requirements can be summarised as follows:
High-protein diets are a thing of the past.
Your diet should include sufficient protein from a wide range of sources including fish, fowl, vegetables, legumes and green-leaved plants. Avoid sources of protein which also contain saturated fats (red meat, sausages and hamburgers).
During intensive training programmes, you may benefit from supplements of certain amino acids. If you wish to find out more about these supplements, speak to your doctor.
Fats and Fatty Acids
Fats are long-chained molecules constructed from the fatty acids and glycerol. Both are obtained from our diets. Fats are found in both animals and plants. They can be saturated (those found in red meats) or unsaturated (plants and fish). Saturated fats have high melting points and are therefore solid at room temperature (eg lard and butter). In contrast, unsaturated fats have low melting points and form oils at room temperature (eg Vegetable oil’, peanut oil and olive oil).
Today, saturated fats are accepted as being ‘unhealthy’, predisposing us, as they do, to heart attacks, strokes, diabetes, gall-stones and certain types of cancer. However, you have to be very careful about the ‘polyunsaturated products’ that you buy. Butter is hard because it contains a lot of saturated fats. Butter substitutes contain polyunsaturated fats but saturated fats must also be present for the margarine to be speadable – pouring margarine on your toast would not be a very successful marketing concept! Unfortunately, some margarines have such a high saturated fat content that they are not significantly different from butter. When buying polyunsaturated products, choose those articles which claim to be extra low in fat (eg low fat cream and butters and skimmed milk), but check the contents list for the proportion of saturates and polyunsaturates.
Grilling and microwaving food provide healthy alternatives to frying either with a saturated fat (lard or butter) or a polyunsaturate (vegetable oil). It is easy to make body fat but much harder to lose it again! Most of the excess energy from carbohydrates that is not immediately used or stored as glycogen is converted into fat. Fats, however, cannot be converted into carbohydrates. Fats are a great energy source and are evolution’s answer to storing energy on a long-term basis.
Unfortunately, because the process of turning fat into energy is relatively slow and can only take place when sugar is being ‘burnt’, as far as our training programme is concerned, fat is really only of use to us in the endurance marches, endurance cycling and the marathon and ultra marathon. This is one of the reasons why once you have laid down fat it is so difficult to get rid of it! In the West, up to 30 per cent of our energy comes in the form of fats and much of this becomes stored in deposits under the skin. In contrast, the leaner peoples of the Third World have diets which are composed of 10 per cent fat or less. The Army and all serious athletes aim for this lower figure. This does require a special effort on your part and a very carefully chosen diet, where skimmed milk is substituted for whole-fat milk; margarine is eaten instead of butter; cottage cheese is exchanged for Cheddar; sausages and hamburgers, if eaten at all, are grilled; lard is rejected in favour of vegetable oil, and fish and chicken replace meat. Remember, even unsaturated fats should be eaten in minimal quantities. In the same way as there are essential amino acids, there are essential polyunsaturated fatty acids (PUFAs). These are only present in fish and plant oils. The best sources are sunflower and safflower seed oils, cod liver oil and the meat of herrings, mackerel and salmon. The PUFAs have two main jobs. Firstly, they are essential to the well-being of all tissue and organs. Secondly, they play a vital role in the synthesis of body chemicals called prostaglandins, which in turn play important roles in tissue-healing and repair.
As with amino acids, it is possible to buy fatty-acid supplements for athletes. The biochemical process that leads to the synthesis of the prostaglandins is long and slow – extremely so in some people. In recognition of this, doctors have recommended that some athletes take supplements of gamma-linolenic acid during their peak training periods. One commercial source of gamma-linolenic acid is the oil of the evening primrose. Current medical advice concerning fats can be summarised as follows:
Not more than 30 per cent of your daily energy should come from fats. Athletes, elite soldiers and anybody seriously interested in keeping fit and remaining healthy should aim at the lower figure of 10 per cent.
This target can only be attained with willpower and a careful diet. Unsaturated fats should be substituted for saturated fats at every opportunity, but be careful of the pitfalls. The essential polyunsaturated fatty acids cannot be synthesised by the body. They are available from fish oils, some fish meat and plant oils. Gamma-linolenic acid may be beneficial during peak training periods.
Cholesterol and Heart Disease
The subject of cholesterol intake and its role in heart disease is complex and controversial. Part of the problem is that we produce our own cholesterol and the body tends to make more as the amount in our diet is reduced. However, all the experts accept that too much cholesterol leads to heart disease since it tends to clog the arteries, particularly the artery which supplies blood to the heart itself.
Cholesterol is present in meat and dairy products but particularly high levels are present in eggs. Indeed, some surgeons have been known to grade the severity of their patient’s disease in terms of their likely egg consumption! Removing the fat from meat, grilling meat, avoiding hamburgers and sausages, reducing your intake of dairy products and eating no more than one or two eggs each week should reduce your cholesterol consumption. There are other factors promoting heart disease. Current medical recommendations include: stop smoking; it damages both the heart and the insides of the arteries.
If your blood pressure is high, take steps to reduce it. Work with your doctor to identify those factors in your diet or lifestyle that may be contributing to your high blood pressure. If all else fails, ensure that you are prescribed the appropriate hypotensive drugs.
Aim for a balanced lifestyle with the minimum of stress. Remember, your life is in the hands of the people who make you angry.
Take regular, moderate exercise, with sessions lasting 30 minutes or more. This conditions your heart. Exercise on its own is not the answer. If you do not correct predisposing factors in your diet and lifestyle, even regular marathons will not protect you against coronary heart disease and atherosclerosis.
Complex and Simple Sugars
The complex sugars present in animal muscle (glycogen) and root crops and cereals (starch) are long, branched chains, built by adding many simple sugars together. The complex sugars are just a good way of storing sugar until it is needed. In humans and animals, glycogen is broken down in the muscles to produce the simple sugar, glucose, which serves as the ‘fuel for life’.
Glucose levels in the blood are carefully regulated to ensure that the muscles, brain and other organs are constantly bathed in this energy-producing sugar. Simple sugars, such as glucose, taste sweet and dissolve in water. They are found naturally in fruits, fruit juices and honey. Simple and complex sugars are all part of a group of similar chemicals called carbohydrates.
The simple sugars can be single molecules such as glucose, which are known as monosaccharides, or double molecules such as fructose, the predominant sugar in bananas known as disaccharides, while the complex sugars are called polysaccharides. Rather than high-fat and high-protein diets which are unhealthy and frowned upon, the person in training needs a high-carbohydrate diet. Some 50 to 60 per cent of our energy intake should come from sugars. However, these should be the complex carbohydrates, such as starch – and to a certain extent glycogen from animal muscle – and not the simple sugars.
The simple sugars rot teeth, and large amounts taken over a short period can damage the liver. They can produce a very high blood sugar level, and as this is brought under control, the blood sugar level can then ‘rebound’ to very low levels, resulting in shaking, dizziness and general weakness.
The other problem with simple sugars is that sugar-rich convenience foods such as chocolate, crisps, ice-cream, biscuits, cake, and popcorn, to name just a few, are not only rich in sugar but they are also rich in fat. The convenience foods are therefore self-defeating since the whole point of a high-carbohydrate diet is to obtain our energy from sugars instead of fats!
Competitive sportsmen and women ‘load’ their muscle glycogen before an important sports event. The muscles of sedentary people are limited as to the amount of glycogen that can be stored. After hard exercise, however, very much more sugar can be stored in the muscles as glycogen. What happens is that two to three hours after hard, intensive exercise, the sugar stores are depleted and the athlete’s body begins to burn fatty acids. So, for a brief time after exercise, fat metabolism takes care of all the athlete’s energy needs. If, at this point, the athlete eats a high-carbohydrate meal, almost all of the available sugar goes into the muscles as glycogen.
The meal recommended by doctors for professional athletes is cereal with a little skimmed milk and the syrup from canned fruit, washed down with a high-energy glucose drink. Very little fat is present in this meal and the fruit syrup replaces the potassium lost in sweat. Also note that the emphasis here is on starch rather than the simple sugars. Complex sugars have to be broken down in our bowels. They are therefore absorbed more slowly and are less likely to cause wild fluctuations in blood sugar levels.
There are some complex carbohydrates, for example cellulose, that we cannot digest. Animals such as sheep and cows only manage to use cellulose as an energy source because they have bacteria in their guts which digest this complex sugar for them. These indigestible carbohydrates are important in our diets too. We call them ‘fibre’. Fibre adds bulk to our food and gives that satisfying feeling of being full without over-eating! Fibre also keeps the bowels moving and prevents the harmful build-up of the chemicals which could cause cancer. Finally, fibre absorbs water and so softens our stools, thus preventing the bowel damage and haemorrhoids which result from straining to expel our stools.
Fruits and plant products are high in fibre, but a word of caution. Because these indigestible carbohydrates cannot supply us with energy, and in absorbing water tend to extend the bowel, high-fibre foods should not form a significant part of our diets during periods of peak training. In other words, the amount of fibre in our diets should vary with the intensity of our training and consequent energy requirements.
Some 50-60 per cent of our energy should come from sugars.
The complex carbohydrates such as starch are better sources of energy than the simple sugars. After intensive exercise, the muscles can be loaded with glycogen by eating a meal rich in sugar. Carbohydrate-rich diets are beneficial during intensive training periods. Indigestible sugars or ‘fibre should form an important part of our diet but not during periods of peak training.
Vitamins are a range of chemicals needed by the body but usually in quite small amounts. They have various roles but most perform some vital function in body chemistry. It is generally accepted that people on well-balanced diets do not require vitamin supplements. On the other hand, athletes on high-carbohydrate or other unusual diets may require regular vitamin supplements. Vitamins come in two varieties, depending on whether they dissolve in water or fat. The fat-soluble vitamins (A, D, E and K) are stored in our body fat and are slowly released as the fat is broken down to be used as energy. In contrast, the water-soluble vitamins (C and B) cannot be stored in the body and are required in regular daily amounts. Vitamin A: Vitamin A is found in animal fats and fish oils. Deficiency is associated with increased infections, night blindness and stunted growth. It is important in the maintenance of healthy skin. It is also a powerful antioxidant and part of the body’s defence against free radicals. Free radicals have assumed more importance recently as the food industry has started to irradiate food to extend its shelf-life. Radiation produces free radicals.
The World Health Organisation, concerned by this problem, has estimated that around one third of the world’s population is deficient in this vitamin. Nevertheless, in the West, athletes and sportsmen/women on well-balanced diets are very unlikely to be deficient in vitamin A. Cod liver oil is a very good source not only of vitamin A but the essential polyunsaturated fatty acids. However, a word of caution! Over-dosing on vitamin A will result in fatal liver damage. Polar bear liver is an extremely rich source of this vitamin and has been responsible for the deaths of certain polar explorers.
Trappers in seventeenth century Canada were often forced to survive the winter on the flesh and offal of trapped animals. Although food was in plentiful supply, many died under mysterious circumstances and it is now believed that hypervitaminosis A was responsible.
Vitamin D: This vitamin is found in fish oil and dairy products but is also synthesised in the skin in bright sunlight. Vitamin D deficiency, which can result in a condition known as ‘rickets’, is only seen in heavily-clothed people living in areas enjoying very little sunshine.
Vitamin E: A deficiency of this vitamin may affect a person’s ability to reach peak performance. It is important in the maintenance and repair of muscle and improves the amount of anaerobic energy that can be generated in muscles. There is no evidence, however, that increased intake of vitamin E improves overall performance. Animal fats and dairy products, particularly eggs, are good sources of this vitamin.
Vitamin C: Vitamin C has been postulated to help the body fight infections and even protect against cancer. However, expert opinion remains divided. It is certainly involved in the maintenance and healing of soft tissue. Vitamin C is water-soluble and a dose of around 60 mg is required each day from our diet. Fruit and green vegetables are rich sources of this vitamin. Vitamin B: This is really a complex of some 12 water-soluble vitamins. The better known include thiamine, riboflavin, niacin, pantothenic acid, pyri-doxine, the cobalamins, the folates, biotin and inositol. Many of these substances are involved in sugar metabolism and even relatively mild deficiencies may be expected adversely to affect training. Sources of the major B vitamins include:
Thiamine (Bl)Wheat germ, oatmeal and yeast.
Riboflavin (B2)Yeasts, peas and beans.
NiacinMany plant and animal foods.
Pyridoxine (B6)Synthesised in the liver from common, naturally-occurring precursors.
FolateGreen vegetables and meat.
Cobalamins (B12) Meat and animal products.
BiotinEggs and dairy products.
Pantothenic acid Many animal and plant sources.
Vitamin Ksynthesised by bacteria in our intestines. Also present in green leafy vegetables, meat and dairy products.
Plays an important role in blood clotting.
The current medical advice to sportsmen and women on vitamin intake can be summarised as follows:
Vitamin deficiency can adversely affect training, but most well-balanced diets contain sufficient vitamins. There may be an increased demand for some vitamins during peak training periods. Oral contraceptives and smoking increase the body’s demand for vitamins B, C and E. Vitamin supplements are also beneficial for those on carbohydrate-rich diets. The fat-soluble vitamins should be taken before peak training, while the water-soluble ones should be taken daily during peak training. & A greatly increased intake of vitamins will not improve performance and, in the case of vitamin A, could have fatal consequences.
Some 15 trace elements perform a range of important functions in the body and are required in varying amounts. During peak training sessions, some minerals may be lost and will need to be replaced either by supplements or from the diet.
Sodium and Potassium: There is ample sodium in the human body but potassium is lost in sweat during intense training. It can be replaced by eating fruit or drinking fruit juice.
Calcium: Calcium phosphate is responsible for the rigidity of bone. It is not ‘lost’ within the bone but is continually turning over. A higher flux occurs during strenuous activity. Calcium also has a vital role in muscle contraction. Inevitably, some calcium is lost from the body and needs to be replaced. The major source is dairy products such as milk and cheese. Removing the fat, eg by skimming milk, does not reduce the calcium content. Copper: Copper is important in a wide range of functions, including protecting the body from the sorts of minor injury which occur during peak training. Very little copper is flushed from the body with the urine, but it is lost in sweat. Moderate supplements should be considered after endurance exercises or after training in a hot gym or outdoors in full sunshine. Chromium: This mineral is an important co-factor in sugar chemistry. Studies have shown that athletes lose twice as much chromium in their urine after exercise than on rest days.
Iron: Iron deficiency results in anaemia, and even mild anaemias reduce the potential to undertake aerobic exercise. Anaemia can result from loss of blood, too little iron in the diet, impaired iron absorption from the intestine or some other problem in blood synthesis. There is usually more than sufficient iron in the well-balanced diet, but it can become limited in diets lacking red meat and green vegetables. Women who experience prolonged menstrual bleeding may never have sufficient iron in their diets, particularly if they are vegetarian or vegan.
Liver is a particularly good source of iron and a good natural dietary supplement. Iron supplements should be taken under medical advice since they can be dangerous. Anyone suspecting that they are either anaemic or iron-deficient should consult their doctor.
Magnesium: Magnesium is intimately associated with energy production in the body. It is widely present in food, particularly green plants. Ample amounts should be present in almost all diets. Nevertheless, studies have shown that blood magnesium levels drop precipitously after heavy exercise. Selenium: Selenium is required in extremely small amounts but is essential. It is a vital co-factor for the anti-oxidant enzyme, glutathione peroxidase. This enzyme helps repair tissue damage, which can occur during vigorous exercise, and it also helps to protect the body by mopping up free radicals. Zinc: Zinc is an important co-factor for more than 100 enzymes, including those involved in energy production in the muscles. Approximately 60 per cent of zinc in the human body is found in the muscles. Some athletes in competitive sports take zinc supplements. It is recommended that intake should be started just before, and continued throughout, peak training.
Most mineral requirements are present in well-balanced diets.
Those undertaking hard, strenuous exercise may benefit from mineral supplements. Proprietary brands are easily available in the high street but should probably only be taken during periods of peak training.
High-dose or regular iron supplements should only be taken after consultation with your doctor.
Fluids are a vital accompaniment to training. A marathon runner, allowed to eat and drink at will, can expect to lose up to eight per cent of his or her-body weight and 13-14 per cent of his or her total body water in the course of the race. Most of the water is lost through sweat and this serves to concentrate the salts in his or her tissues. It was thought at one time that warm fluids prevented cramping and that a large volume of fluid was emptied from the stomach more quickly than a smaller volume to find its way into the blood. In fact, doctors have discovered that small quantities (100-200 ml or X – XA pt) of a cold drink, taken four to five times an hour, both restore body water and cool the body more effectively than either ingesting larger amounts of fluids or warm fluids.
In summary, small, regular amounts of cold water or a weak glucose solution dramatically restores body water and minimises the risk of dehydration. During exercise, keep away from sugar-rich fizzy drinks. You can start drinking rich, syrupy, energy-packed drinks two to three hours after training, when your water balance has returned to normal. Most importantly, on peak exercise days, keep away from alcohol, which switches off the hormone responsible for controlling water loss. Alcohol also seriously disturbs the mechanism which controls blood sugar; the two major components of a hangover are dehydration and too little sugar in the blood.
If we eat a hearty breakfast, we should only need a light lunch and this will give us a good appetite for our evening meal. When training, the last meal of the day should be eaten in the early evening. A large supper which leaves you feeling bloated is not exactly conducive to a good sleep.
Breakfast: Cereal with milk (skimmed or semi-skimmed if you are watching those fats!), scrambled egg cooked in the microwave, toast made from wholemeal bread, grilled lean, unsmoked bacon, baked beans, tomatoes (tinned or grilled), mushrooms (microwaved). Lunch: A salad with fresh vegetables. Fruit to follow (optional). Dinner: It is possible to eat a varied diet every evening which is also nourishing, healthy and tasty. I recommend that red meat is only eaten once or twice a week. Poultry and fish are very enjoyable substitutes. Rabbit is another meat which contains little fat and is tasty and cheap.
MondayRoast chicken (with skin removed)
WednesdayPasta with lean mince (red meat!)
ThursdayLiver, lightly grilled
SaturdayGrilled steak with fat removed
Eat these meals with as many vegetables as you like, but try not to use butter and oil when cooking them. Vegetables are great steamed! Cook your cabbage in its own juices in a dish in the oven. You can introduce a wide variety of vegetables into your diet by eating salads. A little vinegar and water will add to the taste. Try to avoid mayonnaise and oil-based dressings.
Garlic: This fascinating vegetable is purported to have great medicinal properties. It is said to lower blood pressure and it contains significant amounts of the water-soluble vitamins, B and C, as well as calcium, phosphorus and potassium. It lends an excellent flavour to meals but unfortunately it taints the breath. If taken in sufficiently large quantities, the volatile chemicals responsible for the smell are excreted in sweat, thus producing a fascinating body aroma! Garlic tablets are an excellent alternative to fresh garlic and are odourless.
Kelp: Kelp is dried and powdered seaweed. It contains a wide range of minerals, including sodium chloride, so take it sparingly. It is also a natural source of iodine – vital for thyroid function – and is often recommended for people living in areas where natural sources of iodine are lacking.
The Yeasts: Yeast is an excellent source of protein and the B complex of vitamins. It is also rich in iron. Yeast supplements are said to lower cholesterol and generally perk up your system!
Alfalfa: The green leaves of this legume contain a range of essential amino acids and vitamins. Alfalfa is a good source of vitamin K, which is a necessary co-factor in blood clotting. The leaves of the plant are said to be beneficial in stomach disorders and to perk up a jaded appetite. It is available in tablet form.
Ginseng: For thousands of years, the Chinese have used ginseng to stimulate mental and physical energy. Critics, however, argue that gingseng’s ‘feel-good factor’ is due to its high alcohol content and the presence of the stimulant drug, ephedrine. So take it sparingly! Nevertheless, it has been reported to be beneficial for people with blood and circulation problems, and is purported to help potentiate the absorption of vitamins and minerals. It is available in both capsule and liquid preparations. Yucca: The Indians of the southern United States and Central America have used the ground, succulent leaves of the Yucca ‘tuft-tree’ as a general herbal remedy for a wide range of ailments. Today, it is generally accepted to possess many health-giving properties and there is some evidence that it has anti-inflammatory properties useful in the treatment of arthritis. For those of us living outside the deserts of the Americas, it is available in tablet form from health-food stores and suppliers.
Yoghurt: Yoghurt is a dairy product which contains a living culture of harmless bacteria. It is believed to possess general health-giving properties. Some people, particularly Africans, lack the gut enzyme, lactase, which breaks down the milk sugar, lactose. In the absence of this enzyme, the sugar in milk passes into the large intestine where it is fermented by intestinal bacteria, producing severe flatulence and diarrhoea. This ‘allergy to milk’ can be overcome if it is drunk after a meal of yoghurt, since the bacteria in the yoghurt supply the missing enzyme!