The body of an adult consists of about 60% water. Water is much more important than solid food for the maintenance of vital functions, because without water a person can survive only about 4 days, but without solid food almost 40 days. If you consume even 4% too little fluid for a long time, you can expect serious damage to your health. Therefore, good fluid balance is enormously important for good health.
What is fluid balance?
Only with a balanced fluid balance can the vital functions of the body be optimally maintained. Only with a balanced fluid balance can the vital functions of the body be optimally maintained. A disturbed water balance leads in the long run to diseases and in extreme cases even to death. Since humans have no way of storing water for long periods, they must consume it in sufficient quantities every day. About two-thirds of the fluid is required by the cells and one-third by the bloodstream and tissues. Since humans excrete water daily through urine, bowel movements, respiration and sweat, they must take in the appropriate amount again to maintain fluid balance. Water loss is even greater during vigorous physical exertion and exercise. Fluid intake should be distributed as evenly as possible throughout the day. If the person drinks too much at once, most of it is excreted unused. Nutritionists therefore recommend the consumption of one glass of water per hour. In total, a person should drink 30 ml per kg of body weight per day. Athletes are best advised to add another liter of water per hour of training. Infants and small children have an increased fluid requirement. If a person consumes 0.5% too little fluid, the healthy body reacts with thirst. It should not be ignored under any circumstances. Ideal thirst quenchers are water (clean drinking water, mineral water), unsweetened tea, juice spritzer and – in smaller quantities – coffee.
Function and task
Water is a good solvent for nutrients and is therefore also present in gastric juice, saliva, intestinal juices, bile and pancreatic secretions. The blood is also largely composed of water (90%). In this way, the vital substances absorbed through food are transported to where the body needs them. The small and large intestines extract fluids and nutrients from the predigested food and release them into the bloodstream, from where they are transported to all regions of the body. Blood pressure, osmotic pressure and tissue pressure ensure optimal distribution of the fluid. In this process, the fluid balance primarily makes use of the electrolytes sodium and chlorine. Excess water is excreted through bowel movements and urine. At the same time, drug residues, food toxins and metabolic waste products are removed. A balanced fluid balance is also essential for maintaining a constant body temperature. In a healthy adult, this temperature is between 36 and 37 degrees Celsius. Since water can store and also release a lot of heat without significantly increasing its own temperature, it can also regulate body temperature. A balanced fluid balance is also important because water is involved in many chemical reactions, such as breakdown processes. In tear fluid and also in the intestines, it acts as a lubricant.
Diseases and ailments
Disturbed fluid balance can lead to dehydration (hypohydration) and ultimately to exsiccosis (dehydration). If fluid is no longer adequately excreted, hyperhydration can occur. This is usually the case in people with cardiac and renal insufficiency. Sometimes cerebral edema and death from cardiac and renal failure then occur. Since fluid and electrolyte balance are closely linked, impaired water balance also has consequences for electrolyte functioning. Examples include hypokalemia (potassium deficiency) and hyponatremia (sodium deficiency). An undersupply of water – depending on the extent to which it occurs – can have serious consequences for the human organism.If a person consumes only 4 to 6 percent too little fluid over a long period of time, the body can react with dry mouth, darker, foul-smelling urine, difficulty swallowing, constipation, headaches, fatigue, loss of appetite, muscle cramps and kidney disease. More than 10% too little water can cause disorders of consciousness and even confusion. This is especially common in the elderly, who often simply forget to drink enough water or are unable to self-supply because of their immobility. An undersupply of more than 20% usually leads to life-threatening conditions (kidney failure, circulatory collapse, death). If the unconscious person is found in time, the emergency physicians can help him with infusions (full electrolyte solutions). However, it is not only insufficient fluid intake that can lead to health problems, but also excessive fluid loss that is not compensated for in time. This is usually the case after severe, prolonged diarrhea, vomiting, bleeding and extreme burns. People who (have to) follow a very high protein diet should also drink more fluids. To test whether one’s own fluid balance is balanced, the skin fold test is recommended: the person concerned pulls up a fold of skin on the arm. If it remains in this position for a short time, he should definitely drink more.
