Ch 7 Water and Minerals
WATER AND MINERALS
Chapter 7 - NURS 240
LEARNING OBJECTIVES
Upon completion of this chapter, you will be able to:
Discuss a healthy person’s fluid requirement.
Identify mechanisms maintaining mineral homeostasis.
Identify sources and functions of minerals.
Discuss reasons for reduced sodium intake in Americans.
Explain the benefits of increased calcium and potassium consumption.
Describe the Dietary Approaches to Stop Hypertension (DASH) diet.
WATER
Definition and Importance
Occupies essentially every space within and between body cells.
Involved in virtually every body function.
Largest single constituent of the human body (averages 60% of total body weight).
Provides shape and structure to cells.
Regulates body temperature.
Aids in digestion and absorption of nutrients.
FUNCTIONS OF WATER
Roles of Water
Transports nutrients and oxygen to cells.
Serves as a solvent for vitamins, minerals, glucose, and amino acids.
Participates in metabolic reactions.
Eliminates waste products.
Major component of mucus and lubricating fluids.
WATER BALANCE
Definition
The dynamic state between water output and intake.
Under normal conditions, output equals intake.
Thirst sensation and vasopressin control daily fluid balance.
WATER OUTPUT
Types of Water Loss
Sensible losses: measured through urine and feces.
Insensible losses: unmeasured losses through respiration and skin.
Factors affecting water loss:
Extreme temperatures, exercise, high altitude, low humidity.
Average Loss
Adults lose approximately 1750-3000 ml of water daily.
WATER INTAKE
Sources
Liquids, metabolism, solid foods.
Average Intake
Approximately 2.5 L/day (80% from fluids, 20% from solid food, 250-350 mL from metabolic water).
WATER RECOMMENDATIONS
Adequate Intake (AI)
Men (19 years and older): 3.7 L/day
Women (19 years and older): 2.7 L/day
Fluid Intake
Should be consistent throughout the day; below AI might not harm healthy individuals.
SENSING ADEQUATE HYDRATION
Indicators
Normal urine color: pale yellow.
Fluid intake should not wait until thirst sensation occurs, particularly in older adults and children.
ESTIMATING BODY FLUID REQUIREMENTS
Simple Method
30 ml/kg of body weight.
Example: 70 kg person requires 2100 ml/day.
Excessive Fluid Intake
Risk of hyponatremia in athletes due to excessive water intake without sodium replacement.
DEHYDRATION
Effects
Impaired mental function and motor control.
Increased body temperature, heart rate while standing or lying down.
Heightened risk of heat stroke.
HYPOVOLEMIA (DEFICIT OF BODY FLUIDS)
Consequences of Inadequate Fluid Intake
1%-2% loss of body weight leads to thirst, fatigue, and discomfort.
7%-10% loss results in dizziness, muscle spasticity, delirium, and exhaustion, potentially leading to death.
Causes of Severe Dehydration
Vomiting, diarrhea, bleeding/hemorrhage.
FLUID AND ELECTROLYTE BALANCE
Regulation Mechanisms
Governed by membranes, concentrations of electrolytes, and hydrostatic pressure.
Cations: sodium (Na+), potassium (K+).
Anions: chloride (Cl-).
Functions
Help regulate nerve/muscle function, acid-base balance, and water balance.
ELECTROLYTES ATTRACT WATER
Fluid Levels Management
Sodium and chloride in extracellular fluid, potassium and phosphate in intracellular fluid.
Osmosis causes fluid movement into compartments with high concentrations of electrolytes.
ELECTROLYTE BALANCE
Role of Kidneys
Filter electrolytes/water from blood and excrete excess in urine.
Imbalances
May occur in dehydration or overhydration, and due to certain medications or disorders.
KEYS TO UNDERSTANDING MINERALS
Mineral Characteristics
Inorganic elements from the earth; not from plants or animals.
Not digested or metabolized; withstand cooking processes.
Essential for tissue structure and body process regulation.
MAJOR VS. TRACE MINERALS
Major Minerals (> 5g in the body)
Include calcium, phosphorus, magnesium, sulfur, sodium, potassium, chloride.
Trace Minerals
Include iron, iodine, zinc, selenium, copper, manganese, fluoride, chromium, molybdenum.
Importance
Both are essential for life.
MINERAL BALANCE
Regulation
Managed by releasing from storage, altering absorption rates, and urinary excretion control.
MINERAL TOXICITY AND INTERACTION
Toxicity Sources
Can arise from excess supplementation, industrial exposure, or food processing errors.
Interactions
Mineral status is influenced by overall dietary intake.
SOURCES OF MINERALS
Food Sources vs. Supplementation
Unrefined foods generally contain more minerals than refined ones.
Importance of Whole Foods
Nutrient needs should primarily come from food rather than supplements.
MAJOR ELECTROLYTES
Key Electrolytes
Sodium, chloride, potassium.
Sodium: most comes from salt; dietary intake varies widely.
SODIUM (Na+)
Absorption and Regulation
Around 98% absorption; homeostasis mainly through urinary excretion.
Mechanism
Salty meals increase thirst; body restores balance through increased sodium excretion by kidneys.
SODIUM INTAKE
Recommendations
AI: 1500 mg for ages 14+; guidelines suggest intake <2300 mg/day.
Average Intake
Average for ages 1+ is 3393 mg/day (2000-5000 mg/day range).
POTASSIUM AND CHLORIDE
Potassium
AI based on median intake of healthy adults.
No upper limit due to healthy body's regulation.
Chloride
Mostly from sodium chloride; AI for adults (19-50 years): 2.3 g/day.
MAJOR MINERALS
Specific Minerals
Calcium: most abundant (99% in bones); balances through vitamin D and parathormone actions.
Phosphorus: second most abundant; usually readily absorbed.
Magnesium: fourth most abundant; stored in bones and soft tissues.
Sulfur: not independent, involved in amino acid and protein structure.
TRACE MINERALS
Health Impact
Both deficiencies and toxicities can cause health issues.
Key trace minerals: iron (oxygen transport in hemoglobin), zinc (cell function), and iodine (thyroid function).
HEALTH PROMOTION
Focus Areas
Promote healthy beverage choices; limit excessive sodium intake.
Address insufficient potassium and calcium intake; adapt a healthy eating pattern.