Click the body parts below to find out the various effects of dehydration. Dehydration Click the body parts on the left to find out the various effects of dehydration. Brain Your brain is 75-85% water and plays a vital role in your body's response to dehydration. It controls water intake through altering thirst and varying the water excretion from your kidneys. Dehydration adversely affects your mental performance. When dehydrated your attention and concentration can decrease by 13% and short term memory by 7%. Early signs that you are mildly dehydrated may include light-headiness, dizziness, irritability and headaches. Dehydration is defined as a 1% or greater loss of body weight as a result of fluid loss. Even at this level of dehydration your physiological and performance responses are impaired. As you get more dehydrated the symptoms get more severe and can lead to clumsiness, dim vision, exhaustion and may even result in delirium. A loss of more than 10% of body weight due to fluid loss can be come life threatening. Mouth Thirst is a good measure of your hydration status. By the time you feel thirsty your body has lost between 2 and 5 cups of water! The production of saliva is vital for good oral health and hygiene but is impaired by dehydration. Saliva neutralises acid created by the bacteria which cause tooth decay. It washes your teeth, lubricates oral membranes and contains vital minerals that enable tooth repair. Water even helps you to swallow! Lungs Your body loses water every time you breath; every day you lose the equivalent of a can of drink just by breathing! The amount of water lost through your lungs is increased by high temperatures, high altitude and dry air. Heart Dehydration can have an impact on the mechanical function of your heart. Cells shrink when dehydrated which may affect the transmission of electrical impulses that stimulate heart muscles to contract. Drinking five or more glasses of water a day can reduce the risk of coronary heart disease. Kidneys Your kidneys control the amount of water in your body; filtering your blood and excreting waste products in your urine, leaving nutrients in the bloodstream. In order for your kidneys to fulfil their main function of excreting waste products they require a minimum amount of water. Your kidneys play a key role in controlling blood pressure. If your kidneys can not function properly due to dehydration it can lead to high blood pressure. Controlling high blood pressure is particularly important because it reduces the risk of cardiovascular disease, including heart attacks and strokes. Stomach Water is a vital component for any healthy diet. Drinking water often helps to curb your appetite. For example, drinking water before a meal can help fill your stomach and decrease your appetite. Water aids digestion through the production of saliva and other digestive juices. Drinking 500ml of water can increase your metabolic rate by 30% and helps to convert food into energy. Bladder Your body loses water through the skin, lungs and faeces, but most water is lost as urine. A reduced urine output is a useful indicator of dehydration and signals the need to increase your water intake. Drinking plenty of water helps prevent urinary tract infections and kidney stones. Skin Your skin acts as a water reservoir and helps with the fluid regulation of your whole body. Being dehydrated can change the appearance of your skin. In mild dehydration your skin may appear flushed, dry and loose with a loss of elasticity and may look older than it is. Water is lost from your body through evaporation from the skin; this is increased by high temperature, high altitude and dry air. In hot climates sweating rates can be as high as 25000ml\hr. Water is also lost from your body through sweat; this is increased during physical performance. Sweating rates of 1-2 litre per hour are typical during moderately hard exercise. A loss of just 1 litre of water will increase your sense of fatigue and impair your performance. Blood Your blood is 75% water and is vital for the transportation of nutrients in your body. Water is vital to many functions in your body including the maintenance of cell structure and transporting oxygen through your blood stream. If you are dehydrated, your blood becomes thicker and your body has to work much too hard to cause it to circulate.