WATER AND ELECTROLYTE BALANCE

Water is considered as the most important nutrient for the body. It forms the greatest component of the human body, making up 50% to 60% of body weight. Lean muscle tissue contains about 73% water. 
Fat tissue is about 20% water. Thus as fat content increases in the body, total body water content declines towards 50%. Water – the most versatile medium for all kinds of chemical reactions constitutes the major portion of our bodies.
Without water, the life processes would cease in a matter of days.
The water content of soft tissues ranges from 70 to 80 per cent while that of bone about 20 per cent.
The body water can be visualised to be distributed mainly in two compartments.
Intracellular fluid - a fluid present in the cells.
Extracellular fluid - a fluid present outside the cells.

The extra cellular water is further sub divided into
water in blood plasma (about 4 per cent);
interstitial water – water in tissue spaces (9 per cent) and
Lymph in the lymphatic vessels (7 per cent). Of all the nutrients, water is the most critical as its absence proves lethal within a few days. Water's importance in the human body can be loosely categorized into four basic functions: transportation vehicle, medium for chemical reactions, lubricant/shock absorber, and temperature regulator.

Regulates body temperature
Moistens tissues in the eyes, nose and mouth
Protects body organs and tissues
Carries nutrients and oxygen to cells
Lubricates joints
Lessens burden the on kidneys and liver by flushing out waste products
Helps dissolve minerals and nutrients to make them accessible to your body. Of all the nutrients, water is the most critical as its absence proves lethal within a few days. Water's importance in the human body can be loosely categorized into four basic functions: transportation vehicle, medium for chemical reactions, lubricant/shock absorber, and temperature regulator.

Regulates body temperature
Moistens tissues in the eyes, nose and mouth
Protects body organs and tissues
Carries nutrients and oxygen to cells
Lubricates joints
Lessens burden the on kidneys and liver by flushing out waste products
Helps dissolve minerals and nutrients to make them accessible to your body. Of all the nutrients, water is the most critical as its absence proves lethal within a few days. Water's importance in the human body can be loosely categorized into four basic functions: transportation vehicle, medium for chemical reactions, lubricant/shock absorber, and temperature regulator.

Regulates body temperature
Moistens tissues in the eyes, nose and mouth
Protects body organs and tissues
Carries nutrients and oxygen to cells
Lubricates joints
Lessens burden the on kidneys and liver by flushing out waste products
Helps dissolve minerals and nutrients to make them accessible to your body. Of all the nutrients, water is the most critical as its absence proves lethal within a few days.

1. KOMAL OJHA PH.D 1 st year WATER AND ELECTROLYTE BALANCE

2. Content Distribution Functions Sources Requirements Water intake and loss Water balance Water intake regulation Water excretion regulation Mechanism of water balance Water imbalance electrolytes balance References

3. Water Water is considered as the most important nutrient for the body. It forms the greatest component of the human body, making up 50% to 60% of body weight. Lean muscle tissue contains about 73%  water.  Fat tissue is about 20%  water. Thus as fat content increases in the body, total body water content declines towards 50%.  Water – the most versatile medium for all kinds of chemical reactions constitutes the major portion of our bodies. Without water, the life processes would cease in a matter of days. The water content of soft tissues ranges from 70 to 80 per cent while that of bone about 20 per cent.

4. Distribution The body water can be visualised to be distributed mainly in two compartments. Intracellular fluid - a fluid present in the cells. Extracellular fluid - a fluid present outside the cells. The extra cellular water is further sub divided into water in blood plasma (about 4 per cent); interstitial water  – water in tissue spaces (9 per cent) and Lymph in the lymphatic vessels (7 per cent).

5. Functions Of all the  nutrients, water is the most critical as its absence proves lethal within a few days. Water's importance in the human body can be loosely categorized into four basic functions: transportation vehicle, medium for chemical reactions, lubricant/shock absorber, and temperature regulator . Regulates body temperature Moistens tissues in the eyes, nose and mouth Protects body organs and tissues Carries nutrients and oxygen to cells Lubricates joints Lessens burden the on kidneys and liver by flushing out waste products Helps dissolve minerals and nutrients to make them accessible to your body

6. Sources Most of the requirement of the water is met by drinking as such. Part of the requirements is met by the foods consumed and water used in cooking and the beverages consumed. A 2000kcal balance diet may provide 500 to 800 ml of water. Metabolic water It also contributes to the source of water. Water, in addition to C0 2 and energy is an end product of combustion of CHO, fat, and protein. Oxidation of 100g each of fat, CHO, and protein yields 107, 55 and 41g of water, respectively. Water derived through metabolism is called metabolic water. Table 2. water content of foods foodstuff Amount g/100g Ash gourd 96.5 Water melon 95.8 Tomato 94 Spinach 92.1 Milk 87.5

7. Requirements The requirement of water depends on a person’s age, weight, and the life style and the climate in which he is living. Table 1. Fluid Requirement per kg of body weight Group Fluid ml/kg Infants 110 10 yr old children 40 Young adults 40 Older adults 30 Elderly adults (>65 Yrs)n 25 Adults (by environ ments temperature) 22.2 °C 22 37.8°C 38

8. Water intake and loss Loss of water from the body i s continuous. The body loses  water via kidney as urine; via the skin in the form of insensible perspiration and as sweat; via the lungs in the expired air; to a small extent via the large intestines in the faeces and through milk during lactation. Water is taken in food and also as drinking water. In addition, water is formed in the tissues by the oxidation of hydrogen released during fat, carbohydrate and protein metabolism. Water intake and source of body water:  Water is taken as drinking water, about 1500 ml (in temperate climate), through food, 1000 ml; and from oxidation of carbohydrates, fats and proteins in tissues, 300 ml. Water loss:  The body loses water through urine, about 1500 ml; via skin 800 ml; via lungs 400 ml and in faeces 100 ml. In a normal individual, the water intake is approximately equal to water lost from the body and thus the water balance of the body is maintained fairly constant.

9. Water Balance Water balance refers to the balance between the amount of water consumed and the amount of water excreted. For optimal functioning of the body, it is essential that the water content of the body should be maintained constant. Body fluids contain solutes (chemical compounds that are soluble in water), which separate into charged particles, or ions, when dissolved in water. Intracellular fluids are high in potassium and phosphate ions, while interstitial fluids are high in sodium and chloride ions. These ions help to maintain the amount of fluids both within and outside the cells. Water molecules follow the solutes moving across cell membranes from a lower to higher solute concentration to maintain homeostasis.

10. Water Intake Regulation When there is excessive loss of water from the body, the concentration of solutes in the blood becomes too high and the solutes attract water from the salivary glands, making the mouth dry and causing a person to feel thirsty. Heat, intense physical activity (profuse sweating), diarrhoea , vomiting, and excessive urination can all cause excessive fluid loss. A runner can lose upto six cups of fluid in an hour through sweat. If the replenishment of water is not adequate, a state of dehydration can occur. Mild dehydration occurs with a loss of 5 percent or less of a person's bodily fluids, moderate dehydration is a loss of 5 to 10 percent of a person's bodily fluids, and severe dehydration is a loss of 10 to 15 percent of fluids. Severe dehydration can cause death.

11. Water Excretion Regulation The brain and kidneys regulate the amount of water excreted by the body. When the blood volume is low, the concentration of solutes in the blood is high. The brain responds to this situation by stimulating the  pituitary gland  to release a hormone known as Anti diuretic hormone (ADH), which signals the kidneys to reabsorb and recirculate  water. When the individual needs more  water, the kidneys will excrete less and even reabsorb some . When excessive fluid loss occurs, the blood volume, as well as  blood pressure  decreases. The kidneys respond by secreting an  enzyme  called rennin. Rennin activates the blood protein angiotensinogen to convert to angiotensin , which causes the blood vessels to constrict and blood pressure to rise. Angiotensin also activates the adrenal glands to release a hormone called aldosterone . Aldosterone causes the kidneys to retain sodium and water. When the body needs water, less is excreted and more is retained.

12. Mechanism of water balance In the body, several mechanisms work together to maintain water balance. One of the most important is thirst. When the body needs water, nerve centers deep within the brain are stimulated, resulting in the sensation of thirst. The sensation becomes stronger as the body's need for water increases, motivating a person to drink the needed fluids. When the body has excess water, thirst is suppressed . Another mechanism for maintaining water balance involves the pituitary gland (located at the base of the brain) and the kidneys. When the body is low in water, the pituitary gland secretes antidiuretic hormone (also called vasopressin) into the bloodstream. Antidiuretic hormone stimulates the kidneys to conserve water and excrete less urine. When the body has excess water, the pituitary gland secretes little antidiuretic hormone, enabling the kidneys to excrete excess water as urine . The body can move water from one area to another as needed. When water loss is severe, the amount of water in the bloodstream decreases, so the body moves water from inside the cells to the bloodstream until it can be replaced through increased intake of fluids. When the body has excess water, the amount of water in the bloodstream increases, so the body moves  water from the bloodstream into and around the cells. In this way, blood volume and blood pressure can be kept relatively constant.

13. Water imbalance Too much water – whatever amount the kidneys are unable to excrete – can be toxic, but an excessive amount would have to approach many liters each day. Most people have little risk of drinking too much water, but problems do accompany some disease states and mental disorders. When water exceeds the kidney’s capacity to excrete, blurred vision is one resulting symptom. Water Intoxication Water intoxication occurs when there is too much fluid in the body. Excess fluid may collect in body tissues, particularly in the feet and legs resulting in a condition called  oedema . Excess consumption of fluids, as well as kidney disorders that reduce urine output, may contribute to water intoxication. The symptoms of water intoxication are confusion, convulsions, and, in extreme cases, death .

14. Cont….. Dehydration Dehydration of the body results when water is not taken in adequate amounts to make up the water loss. Dehydration occurs rapidly in severe diarrhea and vomiting in infants and children. Some clinical signs of dehydration include dry skin, less frequent urination,  fatigue, light-headedness, dark-colored urine, dry mouth, and lack of skin elasticity. Often, increased fluid intake and replacement of lost electrolytes are sufficient oral rehydration therapy for mild dehydration. In cases of severe dehydration, it may be necessary to hospitalize the person and restore fluid balance through intravenous fluid replacement.

15. Electrolyte balance Electrolytes are the chemicals dissolved in the body fluid. Sodium and potassium are two of the electrolytes essential for proper body function. Several foods that we eat provide these electrolytes, but often they are not in the correct proportion. Sodium chloride is found mostly in extracellular fluid, while potassium and phosphate are the main ions in the intracellular fluid. Sodium Potassium Chloride

16. Sodium Sodium is the major positive ion of the extracellular fluid. It is important for maintaining Fluid balance Muscle irritability Acid-base balance Conducting nerve impulses and osmotic pressure. When combined with chloride, the resulting substance is sodium chloride or table salt. Excess sodium (such as that obtained from dietary sources) is excreted in the urine. Fluid balance throughout the body depends partly on varied sodium concentrations among the water-containing compartments in the body. In a normal man the extracellular fluids contain 2175 mEq . of Na and intracellular fluids about 375 mEq . In addition about 900 mEq of Na is present in the bones, making a total of about 3450 mEq . (200g. of Nacl ) in the whole body.

17. Cont…. Intake of sodium: Dietary intake of sodium is very variable. Most normal people ingest 5 to 20g. NaCl /day, corresponding to 70 to 350 mEq . of Na. The food as served contains about 200 mEq . Na/day. In general, foods as such, contain relatively little sodium, but large amounts may be added in cooking. In most forms of processing and preservation, salt is added. Butter and many other foods are commonly salted in preparation . Output of sodium: Sodium is lost through sweat, faeces and urine. In normal conditions, the losses through the first two routes are minimal, and a bulk of it is lost in urine. The sweat loss is variable and can be decreased by adaptation to heat. Most of the daily output of sodium is in the urine which usually contains 100-150mEq./24 hrs., and reflects the dietary intake.

18. Cont.. Table  : Sodium balance in man ( mmoles /day ) a- --- Variable with environmental temperature and humidity and physical activity b- --- Negligible in basal state but can be high in diarrhoeal diseases . Source Sodium input Source Sodium output Food and   water 100-400 Sweat Faeces Urine a b Total 100-400 100-400 Men doing hard work in hot humid climates, as in mines suffer from heat cramps, i.e., intense and painful contractions of skeletal muscle. This is due to NaCl  deficiency caused by loss of NaCl from the body by excessive sweating .

19. Cont…. Increased sodium level  in the blood  ( hypernatremia )  occurs whenever there is excess sodium in relation to water. There are numerous causes of hypernatremia ; which include kidney disease, too little water intake, and loss of water due to diarrhea and/or vomiting. A decreased concentration of sodium ( hyponatremia )  occurs whenever there is a relative increase in the amount of body water relative to sodium. This occurs in some diseases of the liver and kidney, in patients with congestive heart failure, in burn victims etc . A normal blood sodium level is 135 - 145 milliEquivalents /liter ( mEq /L), or in international units, 135 - 145 millimoles /liter ( mmol /L ).

20. Potassium Potassium performs  functions  similar to those of sodium, except that it is the main positive ion found inside(intracellular), cells. Potassium is vital to fluid balance and nerve transmission. The potassium content of foodstuffs is very variable.  Intake of potassium: The intake of K+ is largely from diet with some contribution from drinking water. Natural diets provide from 50 to 150 mEq . K/day. Most of the common foods contain moderate amounts. Cereals (including rice and wheat), cheese, eggs, fats and almost all fresh fruits contain less than 8 mEq . K/100g. and have been used in planning low potassium diets . a and b – 5% loss through sweat and faeces Source Sodium input Source Sodium output Food and  water 100-400 Sweat Faeces Urine a b Total 100-400 100-400

21. Cont…. Output of potassium: Excretion of potassium is through sweat, faeces and urine, Urinary excretion alone accounts for 95% of the total intake. The output of potassium in the urine closely reflects the dietary intake. The adreno - cortical hormones cause increased potassium excretion in the urine. Excessive production of aldosterone causes large losses of potassium in the urine and consequent deficiency in the cells and a low level in the blood. Increased potassium concentration is known as  hyperkalemia .  Since potassium is normally excreted by the kidneys, disorders that decrease the function of the kidneys can result in  hyperkalemia . Certain medications may also predispose an individual to  hyperkalemia . Hypokalemia , or decreased potassium , can arise due to kidney diseases; excessive loss due to heavy sweating, vomiting, or diarrhea, eating disorders, certain medications, or other causes .

22. Chloride ( Cl -) Chloride is the major negative ion of extracellular fluid. Sea water has almost the same concentration of chloride ion as human body fluids. Chloride also plays a role in helping the body maintain a normal balance of fluids. The important functions of chloride are maintenance of ECF acid-base balance and osmotic pressure. It is also essential for the secretion of hydrochloric acid in the stomach. The balance of chloride ion ( Cl -) is closely regulated by the body. Significant increases or decreases in chloride can have deleterious or even fatal consequences. The total body chloride content is about 2150 mmoles in a 60 kg man. Increased level of chloride ( hyperchloremia ):  may be seen in diarrhoea , certain kidney diseases, and sometimes in over activity of the parathyroid glands. Decreased chloride level ( hypochloremia ):  Chloride is normally lost in the urine, sweat, and stomach secretions. Excessive loss can occur from heavy sweating, vomiting, and adrenal gland and kidney disease . The normal range for serum chloride is 98 - 108 mmol /L .

23. References Gordon Wardlaw Gordon M. & Insel Paul M., 1992, Contemporary Nutrition, Mosby year Book, Boston p-p 293-298. Swaminathan , M. 1997, Essentials of Food and Nutrition, vol I Second edition, BAPPCO, Bangalore.p -p 432-437 . Bamji , M. S, Prahlad Rao.N and Vinodini Reddy,(2003), Text book of Human Nutrition, Oxford & IBH Publishing Co. Pvt. Ltd, New Delhi pp 104-110. Davidson. S.S. and Passmore R. (1966), Human Nutrition and Dietetics, the Williams and Wilkins Co. pp 134-143. http://www.icmr.nic.in/ijmr/2009/november/1126.pdf http://www.8sxe.com/html/Diet---Nutrition/200907/12-511.html

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