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NUTRITION: MINERALS
 
MINERALS
 

Minerals are essential for healthy and active lifestyles and are classed as major or trace minerals according to their contribution to our health. Minerals serve as constituents of enzymes, hormones and vitamins. They help in body structure (bones & teeth), function (maintaining heart rhythm, muscle contractility..), and help regulate cellular metabolism as parts of enzymes and hormones. They also combine with other chemicals such as calcium and phosphate in bones or exist singularly, e.g. calcium in body fluids. A summary of their various sources, deficiencies, excesses etc are shown below. The precise nature of minerals (not mentioned in this list) such as boron, nickel, molybdenum, lithium is still relatively unknown.

Major Minerals
Mineral
RDA(mg) M
RDA(mg) W
Dietary Sources Body Functions Deficiency Excess
Calcium 1200 (800mg for adults 25+) 1200

Milk, cheese, yoghurt, canned fish are rich sources, dark green leafy vegetables

Bone & teeth formation, blood clotting, nerve transmission Stunted growth, rickets, osteoporosis, convulsion Not reported in humans
Phosphorous 1200 (800 mg for adults 25+) 1200 Milk, cheese, eggs, meat, fish, grains Bone & teeth formation, acid-base balance Bone weakness Loss of calcium & demineralisation of bone Erosion of jaw
Potassium 2000 2000 Most foods, leafy vegetables, potatoes, bananas, milk, meat, coffee, tea Fluid balance, nerve transmission, acid-base balance Cramps, irregular cardiac rhythm, confusion, loss of appetite, can be life-threatening None if kidneys function correctly, if poor kidney function, potassium build up and cardiac rhythm problems
Sulphur Unknown Unknown Obtained as part of dietary protein Acid-base balance, liver function Unlikely with adequate diet Unknown
Sodium 1100-3300 1100-3300 Common salt & occurs naturally in many food types Acid-base balance, body function, nerve function Muscle cramps, mental apathy, reduced appetite High-blood pressure
Chloride 700 700 Part of salt containing food, some vegetables and fruit Important part of extracellular fluids Unlikely with adequate diet With sodium leads to high blood pressure
Magnesium 350 280 In most foods, whole grain cereals, nuts, spinach Involved in enzyme activation in protein synthesis Growth failure, disturbances in, behaviour, spasms, weakness, hinders training adaptation Diarrhoea
Trace Minerals
Mineral
RDA (mg) W
RDA (mg) M
Dietary Sources Body Functions Deficiency Excess
Iron 10 15 Red meat, offal, eggs, bread, cereals, flour, vegetables Constituent of haemoglobin & enzymes involved in energy metabolism Iron deficiency, anaemia, weakness, decreased resistance to infection Siderosis, Cirrhosis of liver
Fluoride 1.5-4.0 1.5-4.0 Tea, fish, fluoridated water, toothpaste Maintaining bone structure Tooth decay Teeth Mottling, increased bone density, neurological disorders
Zinc 15 12 Milk, cheese, eggs, meat, fish, whole-grain cereals, pulses Constituent of digestive enzymes Growth failure, small sex glands Fever, nausea, vomiting, diarrhoea
Copper 1.5-3.0* 1.5-3.0 Fish, green vegetables, liver, meats, drinking water Constituent of enzymes within the iron metabolism Anaemia, bone changes Rare metabolic condition (Wilson's disease)
Selenium 0.070 0.0055 Cereals, meat, fish, offal, cheese, eggs, grains Functions with Vitamin E Anaemia (rare) Gastrointestinal disorders, lung irritation
Iodine 150 150 Fish, dairy products, vegetables, iodised salt, seaweed Constituent of thyroid hormones Goitre (enlarged thyroid) High intakes depress thyroid activity
Chromium 0.075-025* 0.05-0.25* Nuts, prunes, dark green vegetables, corn, vegetable oils, orange juice, meat Constituent of some enzymes, involved in glucose & energy metabolism Impaired glucose metabolism, not reported in humans Inhibition of enzymes, skin & kidney damage

These are recommended values (revised 1989) from the Food & Nutrition Board, National Academy of Sciences-National Research Council, Washington D.C for Men (M) and Women (W).

* Because there is less information on which to base allowances, these figures are given in the form of ranges.

In general, no vitamin-and-mineral supplements should be required if an athlete is consuming a a variety of foods to cover their energy expenditure. Even though minerals are lost through sweating, sweat loss during exercise usually does not increase mineral requirements above normal values and these can be replaced through correct post-exercise eating and drinking. Furthermore, there is no real evidence that mineral supplements improve exercise capacity. For more information on nutritional supplements click here. However, there are some athletes who may be at risk. For example, sports women who train intensely, often do not match energy intake to energy output or have a lack of dietary iron or calcium due to them trying to reduce their daily energy intake. No single nutrient supplements should be used without a specific medical or nutritional reason (e.g., iron supplements to reverse iron deficiency anaemia).

Many foods such as fortified breakfast cereals and breads have various vitamins and minerals added to them. Therefore, if the diet is low on fresh fruit and vegetables for short periods of time, these fortified foods can help briefly cover the deficit in these essential ingredients. If energy intake is too low (e.g. through a busy lifestyle where meals are regularly missed), then even a balanced diet will not cover the daily health requirements for the recovery, growth and repair of tissues. Studies carried out on German International soccer players demonstrated that their food intake was lacking in the necessary vitamins and minerals needed to maintain physical and mental performance, especially during intense competition and training. This indicates the need for good nutritional habits even at the highest levels of soccer.

Click here to go to the nutrition advice section of Soccer Performance.

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