Dehydration and Fluid Balance

Quenching Thirst and Balancing Losses

• Dehydration occurs when too much water is lost from the body and not replaced, threatening survival
• The first sign of dehydration is thirst, followed by headaches, fatigue, confusion, and an elevated heart rate with a 1% loss of body weight as fluid
• A 2% loss of body weight as fluid impairs physical functioning
• Older adults with blunted thirst should drink regularly throughout the day, regardless of thirst
• Water intoxication occurs when too much plain water floods the body's fluids, disturbing their normal composition, and immediate action is needed to reverse the effects

How Much Water Do I Need to Drink in a Day?

• Fluid needs vary widely among individuals and within the same person in various environmental conditions
• The Institute of Medicine recommends 13 cups of fluid from beverages and drinking water for men and 9 cups for women
• The remaining water need is met from consumed foods, and the body produces water from the breakdown of energy-yielding nutrients
• Sweating increases water needs, with people losing 2-4 gallons of fluid in a day during physical workouts in hot weather

Drinking Water: Types, Safety, and Sources

• Hard water has high concentrations of calcium and magnesium
• Soft water has high sodium content and dissolves cadmium and lead from pipes, which may aggravate hypertension
• Public water is treated with disinfectants, and its safety is ensured through testing and reporting
• Chlorination of public water can cause cancer-related changes in human cells and cancer in laboratory animals

Body Fluids and Minerals

• Minerals form salts that dissolve in body fluids
• When mineral salts dissolve in water, they separate into single, electrically charged particles called ions
• Ions dissolved in water carry electrical current and are called electrolytes
• Water follows salt, and cells regulate water movement by pumping minerals across their membranes
• Water follows the minerals, ensuring proper bodily functions

The Major Minerals

• Calcium is the most abundant mineral in the body, with 99% stored in bones and teeth
• Calcium has two important roles: integral part of bone structure and serving as a bank that can release calcium to body fluids if blood calcium concentration drops
• Calcium is essential for bone formation, and deficiencies can lead to cretinism in infants
• Iodine is essential for the thyroid gland, and deficiencies can cause cretinism and mental retardation
• Iron is a component of hemoglobin and myoglobin, and deficiencies can lead to anemia and impaired oxygen delivery to cells

Iron

• Iron is essential for many enzymes involved in energy metabolism
• Iron is needed for the production of new cells, amino acids, hormones, and neurotransmitters
• The liver packs iron sent from the bone marrow into new red blood cells
• Red blood cells live for about 4 months, and when they die, the spleen and liver break them down, and iron is sent to the bone marrow to be reused
• Iron is lost in nails, hair trimmings, shed skin cells, and digestive tract
• Hepcidin is a hormone that reduces iron absorption from the intestine and release from storage in response to elevated blood iron

Learn about the signs and symptoms of dehydration, its effects on the body, and the importance of fluid balance, especially for older adults.