Water in the human body plays an essential role by carrying carbohydrates and protein through the blood and eliminating excess salt, minerals, and other substances. Adequate hydration also keeps the body cool when temperatures rise and during physical activity. Water in the human body prevents constipation and keeps skin soft and supple. The lungs and mouth need water to function properly, while the joints use water as lubrication.
Every cell in the body relies on water to dissolve chemicals, minerals, and nutrients to make them usable. If the blood lacks sufficient water, it might not flow freely and carry enough oxygen to organs and tissue. The skin might become dry and cracked when water intake falls below recommended levels.
Water in the human body represents about 70 percent of the total weight of the brain. The blood is comprised of about 80 percent water, while the content in the lungs is about 90 percent water. Liquid is also used by fat, muscles, and bones to support optimal health. Water in the human body flushes bacteria from the bladder and might prevent formation of kidney stones. It also prevents constipation and carries waste from the body through feces.
Each day, water in the human body is lost through urine, perspiration, and respiration. It must be replaced daily because the body cannot store water for later use. The amount of water excreted depends upon a person’s level of activity, the outside temperature, individual metabolism, and the amount of liquid consumed in food and beverages. Very active people, and those who live in hot climates, typically need more water because they often produce more sweat.
Children’s bodies contain higher water content than adults and might become dehydrated more quickly. The elderly might need to increase water intake because kidney functions change with age. An older adult might lose up to 2.1 quarts (2 liters) of water a day through normal bodily functions. It is estimated the elderly obtain half that amount each day through food.
Dehydration can become a serious health risk, causing kidney failure. Symptoms include dark, yellow urine, headache, and lack of energy. The lips and skin might become dry, along with a dry mouth. By the time a person feels thirsty, dehydration might already exist, which might hinder concentration and the ability to perform mental or physical tasks.
Most diets provide about half the necessary water in the human body. Nutritionists usually recommend drinking six to eight glasses of water a day to maintain health. These levels might be obtained from soups, fruit, teas, and other foods. Patients who use medications that increase urination might need to up their daily water intake. People suffering from fever, vomiting, or diarrhea might also quickly lose vital fluids.