Lesson 5
SPORTS NUTRITION LESSON FIVE
WATER
- Between 45 and 75% of the body is made from water
- 45% for infants
- 55% for adult females
- 60% for adult males
- All tissues, organs and fluids of the body contain water as an essential constituent
- Keeps lining of mucus membranes, digestive tract and bronchial tubes moist
- Helps lubricate joints and membranes
- Adipose tissue, bones, teeth and hair contain very little water
- The diagram below shows the ‘water ingestion/secretion and absorption’ of the body per day
Functions:
- to transport nutrients throughout the body
- to dissolve substances (such as minerals for absorption)
- hold substances in colloidal suspension
- to remain a liquid over a wide range of temperatures
Requirements in the body:
- Increases at times of: –
- Illness – when the temperature is raised and swelling occurs
- Vomiting or diarrhea – when dehydration occurs
- Lactation – milk production
- Intense or prolonged physical exercise – or at altitude
Homeostasis (fluid balance):
- Balance (homeostasis) is maintained by fluid intake from the sources of food and drink in the diet
- Some water is also produced during the oxidation of absorbed nutrients to provide the body with energy – thus releasing water
- 1 kg of glucose will produce 1/2 litre of water on oxidation
- Some chemical changes, such as the enzymatic and hydrolytic breakdown of nutrients during the digestion of food, involve the uptake of water
- All body fluids contain varying amounts of water, each of which can have a dramatic effect upon fluid balance at times of need
- The fluids in question are:-
- Digestive juices
- Mucus
- Saliva
- Blood
- Lymph
- Sweat
- Urine
Water Gain: - Ingested liquids account for some 1600 ml of water per day
- Most foods have some water content and account for 700 ml – absorbed from the GI tract
- The technical name for the above-ingested forms is ‘preformed water’
- Metabolic water – accounts for some 200 ml/day
- As a result of the metabolic reactions of the body
Water Loss:
- The kidneys will help excrete some 1500 ml/day
- The skin a further 600 ml/day
- 400 ml in evaporation
- 200 ml as sweat
- The lungs will exhale some 300 ml
- The remainder is lost in the feces – 100 ml
Regulating fluid loss:
- Three hormones help regulate fluid loss:-
1. Antidiuretic hormone (ADH)
2. Aldosterone
3. Atrial natriuretic peptide (ANP) - 1 and 2 will slow down fluid loss in the urine
- 3 increases urine flow rate
- at different times in our lives, water can be saved/lost for a variety of reasons
Severe Dehydration
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Water overload
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Exercise / Injury
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Dehydration: Re-hydration
- Dehydration may take mild or severe forms – the severest leading to fatal results
- In all cases, thirst in the mouth is the first sign of the need for fluid intake
- Decreased production of saliva leads to further dryness in the mouth
- Increased blood osmotic pressure is registered in the hypothalamus
- (low water concentration in the blood)
- the hypothalamus will then increase the thirst sensations
- Blood volume also decreases
- This leads to a drop in blood pressure
- Kidneys then release renin
- The release of renin promotes the synthesis of angiotensin II – which is released into the blood
- (Angiotensin II increases thirst sensation)
- As a result of 1, 2 and 3 – thirst sensation is heightened
- The thirst sensation is then quashed by the intake of fluids and the homeostatic balance of fluid is retained water in the Diet:
- Water is an essential nutrient in the body, its very characteristic that chemically there are no changes upon it as it travels through the body making it unique
- As we have seen, under normal conditions, fluid balance (intake: loss) is maintained throughout our lives
- Research is now beginning to show that fluid (water) intake may be of some benefit to those who wish to ‘lose weight’
- The reasons for the belief:
- Water is an appetite suppressant
- Can help metabolize stored fat
- Without water, kidney function is impaired
Appetite-suppressant:
- When the stomach is ‘full’ messages are sent to the brain informing it, and the need to ingest further food is suppressed
- Satiety – “fullness“Metabolizing stored fat:
- When water intake is low (or decreased), the body will cause fat deposits to increase
- Fortunately, when water intake is high, the body will reduce its fat deposits
- (See below for reasons why)
Kidney Function: - The kidneys can only function at efficient levels of performance when there is a plentiful supply of water
- Without this plentiful water supply, some of the kidney functions/workloads are transferred to the liver
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Liver Function- the Metabolism of Fat:
- If the Liver is required to take over some of the functions of the kidney, then one can see it is unable to perform some of its’ functions efficiently
- One function of the Liver is to metabolize stored fat for energy – if this function is impaired (lessened) – then LESS fat is metabolized, more fat remains stored in the body, and weight is increased fluid retention:
- When water is scarce in the body, it holds onto every drop (survival)
- Water is then stored in the extracellular spaces (outside the cells)
- Evidence of this is when one sees swollen feet, legs and hands
- Diuretics can temporarily lessen these effects
- The effect will force out this stored water, but also essential nutrients
- When the opportunity arises (water intake) – the situation is reversed
- By increasing one’s water intake, the body’s stored water can then be released
- Constant water retention may also be the result of excess salt (sodium)
- The more sodium in the body, the more water is required to dilute it before going into the kidneys
- When water is in plentiful supply it dilutes the sodium and helps remove any excess sodium
- Overweight persons require more water than thinner ones – their metabolism is larger and slower
- Acknowledging the above – such persons require more water!
- Muscle tone can also be maintained/improved through greater water intakes – water prevents dehydration in the muscle and aids contractility
- When weight loss is experienced, there is some ‘sagging’ of the skin – shrinking cells are buoyed by water,
- The water intake helps ‘plump’ the skin, and leaves it clear, healthy and resilient
- We have also seen in the Digestive system (Large Intestine) that during times of low intake, the body will retain its stored water supplies
- If water stores are low/ depleted, then absorption of water will occur – and in such cases, it is removed from the colon
- The net result is harder stools and constipation
- Greater intake of water therefore will alleviate constipation and normal bowel function returns
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How much do we need?
- The ‘average’ person requires some 2 litres of water per day
- For every 25 lbs that one is overweight, one requires a further 8 ounces (or 250 ml)
- In hot, humid climates, or during exercise, the requirement will be so much the greater
- During the 1998 Commonwealth Games in Kuala Lumpur (Malaysia), the England Track & Field Team was advised to consume some 7-9 litres of water per day on REST days
- During training and competition, the intake was increased to 9-11 litres per day
- Long-distance and marathon runners were advised to increase their intake from 12 litres upwards
- Although it is unlikely we shall experience such demands under normal circumstances, one can see the demands placed upon the body just to maintain fluid balance
Note,
- Coldwater is absorbed quicker in to the body than warm
- Adding sodium or electrolytes in the right proportions will also speed up absorption rates in times of need
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Electrolyte Balance:
- Although it is NOT an essential part of the curriculum at this stage, there is no harm in discussing electrolyte balance and ‘tonic’ drinks – especially if one is expected to give some advice in the future!
- Isotonic
- This is where the concentration of the liquid (the additives of salts, ions and electrolytes, etc) is the same as the cytosol in the body
- Hypotonic
- The solution consists of a higher water concentration than the proportions of salts, etc which are normally found in the cytosol
- Such solutions can cause the cells of the body to swell as a result of osmosis
- Hypertonic
- The solution contains higher concentrations of the salts, etc than found naturally in the cytosol
- Such solutions can cause the cells of the body to shrink (osmotic pressure)
SUMMARY:
- Plentiful supplies of water can help alleviate the problems of
- Stored fat deposits (metabolize more efficiently by the Liver)
- Fluid retention – removes the water stored in the extracellular spaces
- Water will also help endocrine-gland function
- Natural thirst will return (avoiding dehydration)Supplies of Water:
- Our supplies of water come from one of three sources: –
- Rain
- Spring
- River
- Rainwater – contains small amounts of dissolved gases (oxygen, carbon dioxide and may be dissolved oxides of sulphur and nitrogen [acid rain])
- Springwater – dissolved salts
- River water – impurities such as vegetation and drainage impuritiesClean Water:
- Although we will get it from the tap – it has been through several processes: –
- Settlement
- Filtration
- Sterilization
- Some waters have been ‘fluorinated’
- 1995 European Union regulations laid down strict regulations for the bacteriological and chemical quality of water supplies
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Hard Water:
- Due to the presence of certain mineral salts
- Chiefly the sulphates and bicarbonate variety
- But also magnesium and calcium
- Called hard as it is difficult to give a lather with soap
- It is drinkable
- NOT used for industrial purposes due to the likelihood of mineral salts being deposited onto pipes, boilers, Soft Water:
- Via the process of ‘ion-exchange’
- The ions of calcium and magnesium are exchanged for the ions of sodiumSterilization:
- The organic matter and dissolved oxygen are a natural breeding ground for bacteria
- Infected water supplies give rise to several diseases – mostly eliminated in the west, but unfortunately still prevalent in the developing countries
- Typhoid fever
- Jaundice
- Cholera
- Water is sterilized by adding 0.5 parts per million (ppm) of chlorine
- Water that is to be canned or bottled will be given 1 to 2 ppm of OzoneMineral Water:
- Sales of mineral water in the UK are increasing each year
- Mineral water contains the following mineral salts
- Sodium chloride
- Sodium carbonate
- Sodium bicarbonate
- Salts of calcium and magnesium
- Dissolved mineral salts may amount to anything as low as 0.1 g/l but rarely above 3.5 g/l
- Some mineral waters are of course naturally aerated with carbon dioxide water supplies & Health:
- There is growing evidence that soft water can be linked to increased incidences of coronary heart disease (CHD) in certain geographical areas
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- Soft water may also be deficient in the mineral vanadium
- Soft water is also capable of picking up traces of zinc, calcium, iron, copper and lead – found in pipes
IN REVIEW |
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KEYWORDS and PHRASES
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| TUTOR TALK: Now all that remains to do is for you to answer the questions and return them to the College for marking. Again, well done. |
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