Chapter 8: Water and Minerals Part 1

What are the two main classifications of minerals? Which nutrients fall under each, and what is the amount for an adult per day?

• Major Minerals: Required in amounts >100 mg/day (e.g., Calcium, Phosphorus, Potassium, Sulfur, Sodium, Chloride, Magnesium).

• Trace Minerals: Required in amounts <100 mg/day (e.g., Iron, Zinc, Copper, Manganese, Iodine, Selenium).

What percentage of an adult's body weight is water, and how is water distributed in the body?

• Approximately 60% of body weight is water (≈80 lbs in a 130-lb person).

• Brain and muscles are about 75–80% water, while bones contain about 25% water.

List the five primary functions of water in the body.

1. Transportation: Moves nutrients and wastes.

2. Solvent: Dissolves amino acids, glucose, minerals, etc.

3. Cleansing Agent: Removes small molecules before they accumulate.

4. Lubricant/Cushion: Protects joints, cushions organs, and moistens tissues.

5. Coolant: Helps maintain body temperature.

How does the body maintain water balance, and what roles do the hypothalamus and kidneys play?

The body maintains water balance through mechanisms such as thirst and urine concentration.

The hypothalamus detects changes in blood osmolarity and triggers thirst, while the kidneys regulate water excretion to maintain homeostasis.

What are the primary functions of calcium in the body, and how is calcium balanced?

• Functions: Structural component of bones and teeth; critical for nerve transmission, muscle contraction, blood clotting, and enzyme activation.

• Balance: 99% stored in bones/teeth; blood calcium is tightly regulated by hormones and vitamin D.

• Absorption: 20–30% absorbed, with increased uptake during pregnancy and infancy.

How do phosphorus and calcium work together in bone formation?

• Calcium phosphate salts crystallize on collagen to form the rigid structure of bones and teeth.

• Hydroxyapatite crystals infiltrate the collagen matrix, reinforcing bone strength.

What roles does magnesium play in the body, and what are common issues related to its intake?

• Roles: Acts as a cofactor for hundreds of enzymes, supports energy release, protein synthesis, nerve transmission, and works with calcium in muscle contraction/relaxation.

• Issues: Many individuals consume below the recommended amount, which is linked to conditions such as hypertension, heart failure, and stroke. Toxicity is rare and generally linked to high supplemental doses.

Summarize the functions and homeostasis of sodium in the body.

• Functions: Regulates extracellular fluid volume, acid-base balance, nerve impulses, and muscle contractions.

• Homeostasis: Most sodium is excreted by kidneys; too high intake may lead to hypertension.

• Recommendation: AI of 1500 mg/day; CDRR of 2300 mg/day.

What is the significance of potassium, and what are its dietary sources and recommendations?

• Significance: Vital for cell integrity, nerve transmission, and muscle function; works closely with sodium.

• Sources: Found in bananas, spinach, cantaloupe, oranges, baked potatoes, avocados, and almonds.

• Recommendation: Approximately 3400 mg/day for males and 2600 mg/day for females.

What are the key roles, storage, absorption, and requirements of calcium?

• Roles: Provides structural support for bones and teeth; essential for muscle contraction, nerve transmission, blood clotting, and enzyme activation.

• Storage: 99% is stored in bones and teeth; the remaining 1% is in body fluids, tightly regulated by hormones and vitamin D.

• Absorption: Most adults absorb 20–30% of ingested calcium, with increased uptake during pregnancy and infancy.

• Requirements: Approximately 1000 mg/day for adults (19–50 years) and 1200 mg/day for older adults.

What functions does phosphorus serve and what are its dietary considerations?

• Functions: Works with calcium in forming bones and teeth; acts as a buffer in cellular fluids; is integral to DNA, RNA, ATP, and cell membranes; aids in energy metabolism and enzyme function.

• Storage: More than 80% is stored in bones and teeth.

• Requirements: Approximately 700 mg/day for adults; Tolerable Upper Level (TUL) is about 4000 mg/day.

What are the distribution, roles, and intake recommendations for magnesium?

• Distribution: Only about 1 ounce in a 130-lb person; over half is stored in bones, with the remainder in muscles, heart, liver, and soft tissues.

• Roles: Acts as a cofactor for hundreds of enzymes, assists in energy production, protein synthesis, and nerve/muscle function; works with calcium to regulate muscle contraction and relaxation.

• Requirements: For ages 19–30, males need about 400 mg/day and females 310 mg/day; for ages 31+, males need 420 mg/day and females 320 mg/day; supplemental TUL is 350 mg/day.

Describe the functions of sodium and its recommended intake.

• Functions: Regulates extracellular fluid volume, acid-base balance, nerve impulses, and muscle contractions; part of body sodium is stored with bones.

• Intake: Adequate Intake (AI) is about 1500 mg/day; the Chronic Disease Risk Reduction (CDRR) level is 2300 mg/day; excess intake is linked to hypertension.

What are the major roles and dietary recommendations for potassium?

• Roles: Essential for maintaining intracellular fluid balance, nerve transmission, and muscle contraction; it exchanges with sodium during nerve impulses and muscle contractions.

• Sources: Found in bananas, spinach, cantaloupe, oranges, baked potatoes, avocados, and almonds.

• Requirements: Approximately 3400 mg/day for males and 2600 mg/day for females.

What role does chloride play in the body?

Functions: Acts as the major negative ion in extracellular fluid; pairs with sodium to maintain fluid balance; is a crucial component of hydrochloric acid in the stomach, aiding in digestion; primarily obtained from salt.

***No known diet lacks chloride***

What is the significance of sulfate in the body?

• Functions: Sulfate is the oxidized form of sulfur, required for the synthesis of sulfur-containing compounds that help proteins (such as those in skin, hair, and nails) maintain proper structure.

• Notes: There’s no established recommended intake, and deficiencies are unknown; excessive sulfate in drinking water can cause diarrhea and colon damage.

Define dehydration and describe its initial warning sign.

• Definition: Dehydration occurs when water losses from the body are not replaced adequately, compromising essential physiological functions and threatening survival.

• Initial Warning: The first signal is thirst, which typically indicates that the body has lost about one to two cups of its total fluid.

What happens in the body when dehydration begins, and what symptoms can occur with a 1% fluid loss?

• Blood Pressure Maintenance: The body prioritizes maintaining blood pressure by diverting available water into the blood vessels.

• Symptoms at ~1% Loss: Even a loss of 1% of body weight as fluid can result in headaches, fatigue, confusion or forgetfulness, and an elevated heart rate, signaling the need for immediate hydration.

How does a 2% loss of body weight as fluid affect physical functioning?

Impaired Function: When fluid loss reaches approximately 2% of body weight, physical performance and overall functioning become noticeably impaired, impacting strength, coordination, and cognitive performance.

What additional risks are associated with chronic low fluid intake?

• Mild Consequences: Chronic low intake can lead to symptoms such as persistent thirst, sudden weight loss, dry and cool skin, and dryness in mouth, throat, and other mucosal linings; it may also cause rapid pulse, low blood pressure, muscle weakness, and reduced urine output (often dark yellow or amber).

• Severe Consequences: More extreme dehydration may result in diminished mental clarity, irregular breathing, shock, seizures, coma, cardiac arrest, constipation, dental disease, gallstones, glaucoma, hypertension, kidney stones, complications during pregnancy/childbirth, stroke, and an increased risk of urinary tract infections.

How do caffeinated beverages affect hydration, and do they typically cause dehydration?

• Diuretic Effect: Caffeinated beverages have a mild diuretic effect, meaning they can increase fluid loss.

• Moderation Matters: However, moderate caffeine consumption does not typically lead to dehydration or hinder meeting overall fluid needs, as the body usually compensates when additional water is consumed.

Define water intoxication and explain under what conditions it occurs.

• Definition: Water intoxication happens when the intake of plain water is excessively high, disrupting the normal electrolyte balance and composition of body fluids.

• Occurrence: It is most commonly seen when several gallons of water are consumed within just a few hours, overwhelming the body’s ability to maintain proper fluid and electrolyte balance.

What factors influence daily water needs and what are the recommended Adequate Intakes (AI) for males and females?

• Influencing Factors: Daily water needs vary based on food intake, air temperature, humidity, altitude, and physical activity level.

• Recommendations:
  • Approximately 3.7 liters per day for males and 2.7 liters per day for females (about 30 mL/kg).

• Sources:
  • Most daily water is obtained from beverages, while a smaller percentage comes from water-rich foods (e.g., fruits contain up to 95% water; many meats and cheeses are at least 50% water).

How does sweating affect daily water requirements, and what are the typical fluid losses during physical activity or in hot weather?

• increased Losses: Physical activity, especially in hot conditions, dramatically increases water loss through sweating.

• Quantities:
  • In hot weather, individuals can lose between 2–4 gallons of fluid per day.
  • Athletes may lose more than half a gallon of fluid per hour during intense training.

How do nonalcoholic beverages contribute to fluid intake, and what should be considered when choosing them?

• Contribution: All nonalcoholic beverages help meet daily fluid requirements.

• Nutritional Considerations:
  • Many beverages may also add sugars, sodium, and saturated fats to the diet.
  • Plain water or unsweetened drinks are generally preferred to avoid extra calories or unhealthy additives while still satisfying fluid needs.

What does the phrase “water follows salt” mean in cellular fluid balance?

• Mechanism:
  • Cells do not directly pump water; instead, they actively transport mineral ions (e.g., from sodium chloride) across cell membranes.
  • When mineral salts dissolve, they dissociate into ions, creating concentration gradients.

• Outcome:
  • Water moves passively toward the more concentrated (hypertonic) solution to equalize these concentrations across the membrane.

How does the body maintain fluid and electrolyte balance, and what happens when this balance is disturbed?

• Maintenance:
  • The body uses energy to move electrolytes between compartments via transport proteins (pumps) to maintain proper fluid volumes and electrolyte composition.

• Disruption:
  • Disturbances (e.g., from vomiting or diarrhea) can cause rapid shifts in fluid distribution, potentially leading to medical emergencies due to the loss of critical electrolytes and imbalances in fluid compartments.

How is the pH of body fluids maintained and what roles do minerals play in this process?

• pH Maintenance:
  • The pH is partly maintained by the ionization of water molecules and the contribution of mineral ions.
  • Certain minerals form acids (releasing H⁺ ions) or bases (releasing OH⁻ ions), which influence the overall pH.

• Buffer Systems and Regulation:
  • Buffer systems, including proteins and mineral salts, help stabilize pH by absorbing or releasing H⁺ ions.
  • The kidneys adjust H⁺ excretion and the lungs modulate carbon dioxide levels, both playing essential roles in maintaining acid-base homeostasis.