Chapter 9: Comprehensive Study Guide for Water and Minerals in Human Mineral Nutrition

Functions and Properties of Water

• Essential To Human Life

  • Water ($H_2O$) is the most abundant molecule in the human body and serves as a versatile medium for chemical reactions.

  • It comprises $50\%$ to $70\%$ of the total human body weight.

  • Survival limits: Humans can survive for several weeks without food but only a few days without water.

  • The body cannot store water and loses it continuously through the lungs, skin, urine, and feces.

• Water Distribution Across Body Components

  • Muscle: $73\%$ water.

  • Adipose tissue (Fat): $10\%$ to $20\%$ water.

  • Bone: Approximately $20\%$ water.

  • Total Human Body: $50\%$ to $70\%$ water.

  • Lean tissue correlation: As body fat content increases, the percentage of lean tissue decreases, which leads to a decrease in total body water. Extremely lean athletes may consist of up to $70\%$ body water.

• Universal Solvent and Transport

  • Water is the "universal solvent" because it can dissolve many different solutes.

  • Nutrient Transport: It is an ideal vehicle for transporting water-soluble nutrients, including carbohydrates, proteins, minerals, and many vitamins.

  • Lipid Transport: Although lipids are not water-soluble, they are dispersed in water-based environments by being surrounded by layers of water-soluble proteins.

  • Waste Removal: Metabolism generates waste products that dissolve in water for excretion. For example, the nitrogen portion of amino acids from protein breakdown is converted by the liver into urea, which is then excreted in urine via blood and lymph.

• Medium for Chemical Reactions

  • Water provides the environment for metabolic reactions and is an active participant in many.

  • Metabolic water: A by-product of the metabolism of carbohydrates, lipids, and proteins. It contributes $1$ cup or more per day toward maintaining fluid balance.

• Body Temperature Regulation

  • Water holds heat efficiently, meaning changes in body temperature occur slowly.

  • Perspiration: When the body is overheated, it secretes fluid as perspiration. As this water evaporates through skin pores, it removes heat energy and cools the body.

  • Energy Expenditure: Each quart (approximately $1\,\text{liter}$ or $2\,\text{pounds}$) of evaporated perspiration represents approximately $600\,kcal$.

• Moistening, Lubrication, and Cushioning

  • Saliva: Facilitates the passage of food from the esophagus to the stomach.

  • Mucus: Provides a protective coating throughout the digestive (GI) tract and lungs.

  • Cerebral Spinal Fluid: Cushions the spinal cord and brain.

  • Amniotic Fluid: Acts as a shock absorber in the womb.

  • Lubricating Fluids: Found in knees, other joints, and as tears in the eyes.

Water Balance and Intake

• The Water Balancing Act

  • Fluid balance is maintained through the coordinated efforts of the nervous, endocrine, digestive, and urinary systems which monitor blood pressure and solute concentration.

• Water Intake Recommendations

  • Adequate Intake (AI) for Total Water (Fluid + Food):

    • Women: $2.7\,\text{liters}$ per day ($11$ cups).

    • Men: $3.7\,\text{liters}$ per day ($15$ cups).

  • AI for Fluid Alone:

    • Women: $2.2\,\text{liters}$ ($9$ cups).

    • Men: $3\,\text{liters}$ ($13$ cups).

  • Food Content: Many fruits and vegetables are more than $80\%$ water; many meats are at least $50\%$ water.

• Water Output

  • Urinary System: The greatest source of output. Average loss is $1950\,ml$ ($8.5$ cups) per day. Output below $500\,ml$ is a sign of dehydration.

  • Skin (Insensible): Approximately $1\,\text{liter}$ per day through perspiration.

  • Lungs (Insensible): Exhaled water vapor; difficult to measure.

  • Feces: A small amount is lost daily.

• Fluid Conservation Mechanisms

  • Receptors in the kidneys, blood vessels, and brain monitor blood pressure and solute concentration.

  • Antidiuretic Hormone (ADH): Secreted by the pituitary gland when solute concentration is high; signals the kidneys to reduce water excretion to increase blood volume.

  • Angiotensin: Participates in fluid conservation.

  • Aldosterone: Produced by the adrenal glands when blood volume is low; signals kidneys to conserve sodium and water to increase blood volume.

Dehydration, Urine, and Hydration Status

• Stages and Symptoms of Dehydration

  • $1\%$ to $2\%$ body weight loss: Thirst, loss of appetite, hemoconcentration, tiredness, dizziness, and headaches.

  • $4\%$ loss: Increased severity of tiredness, dizziness, and headaches.

  • $10\%$ loss: Decreased heat tolerance and weakness.

  • Critical Failure: Ultimately leads to kidney failure, coma, and death.

  • Heat Stroke: Strenuous activity in hot, humid conditions can lead to an inability to regulate temperature, unconsciousness, and death.

  • Kidney Stones: Low urine production ($< 500\,ml$ per day) increases risk due to highly concentrated urine.

• Urine Production Indicators

  • Typical production: $1\,\text{liter}$.

  • Concentrated urine: Less than $500\,ml$ ($2$ cups) increases the workload on kidneys.

  • Color Test: Clear or light yellow indicates adequate hydration; dark yellow and pungent indicates poor hydration.

• Thirst Mechanism

  • Thirst is generally a good indicator but can lag behind actual loss during prolonged exercise, illness, or in older adults.

  • Monitoring: Infants and children require close monitoring during vomiting or diarrhea.

  • Athletes: Recommended to consume $2$ to $3$ cups of fluid for every pound lost during exercise.

• Water Intoxication (Hyponatremia)

  • Occurs when water intake exceeds the kidneys' processing ability (maximum of $15\,\text{liters}$ of urine per day for healthy individuals).

  • Result: Severe dilution of blood sodium levels (hyponatremia).

  • Symptoms: Swelling of the brain and nerves, fluid in the lungs. It is a potentially fatal condition.

Sources and Quality of Water

• Hard vs. Soft Water

  • Hard Water: Contains high levels of calcium and magnesium. Soap does not lather well. Found in $89\%$ of North American homes.

  • Soft Water: Contains high levels of sodium. Soap lathers easily and clothes are cleaner. Found naturally in the Pacific Northwest, New England, South Atlantic Gulf States, and Hawaii.

  • Conversion: Commercial softeners exchange calcium and magnesium for sodium.

• Bottled Water vs. Tap Water

  • Consumption: Americans consumed $45\,gallons$ per capita in 2019.

  • Cost: Average American spends $205 annually; industry total is $67 billion.

  • Quality: Much of U.S. bottled water is processed municipal tap water.

  • Environment: Tap water uses pipes; bottled water requires packaging and transport, increasing energy use and waste. Reusable stainless steel bottles are recommended.

• Sparkling and Seltzer Water

  • Production: Carbon dioxide ($CO_2$) is pumped into water, forming carbonic acid.

  • Acidity: pH is between $3$ and $4$, which can erode tooth enamel.

  • Risk Mitigation: Drinking with food increases the pH in the mouth, reducing erosive potential. Citric acid flavorings further lower pH.

Electrolytes and Fluid Regulation

• Distribution of Body Fluids

  • Intracellular Fluid (ICF): Fluid inside cell membranes ($63\%$ of total body fluid).

  • Extracellular Fluid (ECF): Fluid outside cells ($37\%$ total).

    • Interstitual Fluid: Fluid between cells ($30\%$

    • Plasma and Lymph: Fluid portion of blood ($7\%$

• Electrolytes

  • Ions are minerals dissolved in water with positive ($+$

  • Primary Extracellular Ions: Sodium ($Na^+$) and Chloride ($Cl^-$).

  • Primary Intracellular Ions: Potassium ($K^+$) and Phosphate ($PO_4^-$).

• Osmosis and Equilibrium

  • Osmosis: Passive movement of water from high concentration to low concentration through a membrane.

  • Isotonic: Equal concentration of electrolytes on both sides; water movement is in equilibrium.

  • Hypotonic: Intracellular electrolyte concentration is low compared to the environment; water exits the cell, causing it to shrink.

  • Hypertonic: Intracellular electrolyte concentration is higher than the environment; water flows into the cell, potentially causing it to burst.

Minerals: General Overview

• Classification

  • Major Minerals: Requirement is $≥ 100\,mg$ per day.

  • Trace Minerals: Requirement is $< 100\,mg$ per day.

  • Ultratrace Minerals: Present in the diet but not essential to human health.

• Bioavailability and Absorption

  • Majority of absorption occurs in the small intestine.

  • Factors affecting bioavailability: Age, gender, genetics, nutritional status, diet, and prescription drugs.

  • Inhibitors: Fibers such as phytic acid (in grains) and oxalic acid (in spinach) can bind to minerals. High fiber diets can lower iron and zinc absorption.

  • Enhancers: Vitamin C increases iron absorption; Vitamin D increases calcium absorption.

  • Competition: Excess of one mineral (e.g., zinc) can decrease absorption of another (e.g., copper).

  • Source differences: Minerals from animal sources are better absorbed than those from plants due to fewer fiber hindrances.

• Mineral Storage

  • Bone: Calcium, phosphorus, magnesium, and fluoride.

  • Liver: Iron, copper, zinc, and some trace minerals.

  • Other: Muscle tissue, organs, and glands.

  • Bloodstream: Transient minerals maintain fluid balance and supply functions.

• Toxicities and Preservation

  • Toxicity risk: High for trace minerals like iron and copper, especially from supplements. Supplements should not exceed $100\%$ of Daily Values.

  • Processing losses: Minerals are lost from plant foods during refinement. Refined grains (white flour) lose Vitamin E, B vitamins, and most trace minerals; enrichment only adds iron back.

Major Mineral: Sodium ($Na^+$)

• Properties

  • Table salt is sodium chloride ($NaCl$), consisting of $40\%$ sodium and $60\%$ chloride.

  • $1\,\text{tsp}$ of salt = $2400\,mg$ sodium.

• Functions

  • Attracts water to maintain fluid balance.

  • Assists in nerve impulse conduction.

  • Aids absorption of nutrients like glucose.

• Deficiency

  • Symptoms: Muscle cramps, nausea, vomiting, dizziness, shock, and coma.

  • Causes: Low intake combined with excessive perspiration, vomiting, or diarrhea.

• Needs and Intake

  • Adequate Intake (AI):

    • Age $9$ to $13$: $1200\,mg/day$.

    • Age $14$ to $>70$: $1500\,mg/day$.

  • Chronic Disease Risk Reduction Intake (CDRR): Excessive sodium is linked to cardiovascular disease and hypertension. Intakes should be reduced if above $2300\,mg/day$.

  • Consumption: Average American consumes $2300$ to $4700\,mg/day$. About $77\%$ comes from processed food manufacturing.

Major Mineral: Potassium ($K$)

• Functions

  • Principal positively charged ion inside cells ($95\%$ is intracellular).

  • Maintains water balance and nerve impulse transmission.

  • High intake is associated with lower blood pressure.

• Deficiency (Hypokalemia)

  • Symptoms: Loss of appetite, muscle cramps, confusion, constipation, and irregular heartbeat.

  • Causes: Chronic diarrhea, vomiting, laxative/diuretic abuse, alcohol abuse, eating disorders, or very low-calorie diets.

• Needs and Sources

  • AI: $3400\,mg$ (Males), $2600\,mg$ (Females).

  • Daily Value: $4700\,mg$.

  • Sources: Unprocessed foods are best. Milk, potatoes, beef, coffee, tomatoes, and orange juice are major contributors.

  • Toxicity: No Upper Level (UL) set for healthy people; however, poor kidney function can lead to potassium buildup which inhibits heart function.

Major Mineral: Chloride ($Cl^-$)

• Functions

  • Acid-base balance (component of stomach acid, $HCl$).

  • Immune response (used by white blood cells).

  • Nerve function and raising blood pressure.

• Needs and Deficiency

  • AI: $2300\,mg/day$.

  • UL: $3600\,mg/day$.

  • Deficiency: Rare due to high salt intake; can occur with prolonged vomiting (bulimia/flu).

Major Mineral: Calcium ($Ca$)

• Functions

  • Bone and Teeth: Forms $40\%$ of minerals in the body; active component of hydroxyapatite.

  • Nerve/Muscle: Activates muscle contraction and neurotransmitter release.

  • Metabolism: Regulates enzymes, hormone responses, cell differentiation, and blood clotting.

• Regulation and Deficiency

  • Regulation: If blood calcium is low, bones release calcium, intestines increase absorption, and kidneys retain more in the blood.

  • Tetany: A deficiency symptom where muscles cannot relax, causing stiffness or involuntary twitching.

• Osteoporosis

  • Definition: Porous bones with low mineral density; T-score of $-2.5$ or lower.

  • Type 1: Postmenopausal (ages $50$ to $60$); linked to low estrogen.

  • Type 2: Later life (ages $70$ to $75$); breakdown of cortical and trabecular bone in both sexes.

  • Hip Fractures: $20\%$ to $30\%$ of patients die within $12$ months post-fracture.

• Bone Health Assessment

  • Dual energy X-ray absorptiometry (DXA): The most accurate test.

    • Normal: $0$ to $-1$.

    • Osteopenia: $-1$ to $-2.4$.

    • Osteoporosis: $≤ -2.5$.

• Absorption Factors

  • Enhancers: High need (growth/pregnancy), Vitamin D, PTH, lactose, acidic stomach environment.

  • Inhibitors: Phytic acid, oxalates, tannins, excess phosphorus/magnesium/zinc, and aging.

• Needs and Supplements

  • RDA: $1000\,mg/day$; DV: $1300\,mg/day$.

  • Supplement limit: Keep to $≥ 500\,mg$ per dose. Look for USP symbol. Avoid dolomite or bone meal due to lead risk.

Major Mineral: Phosphorus ($P$)

• Functions

  • Second most abundant mineral.

  • Component of hydroxyapatite (bones/teeth), DNA, RNA, ATP, and phospholipids.

  • Acts as a blood pH buffer.

• Needs and Sources

  • RDA: $700\,mg$ (adults); Average intake: $1000$ to $1600\,mg/day$.

  • Sources: Milk, cheese, meat, bread. High absorption ($55\%$ to $80\%$

  • UL: $4000\,mg/day$. Excess can lead to tissue calcification and bone loss if calcium is low.

Major Mineral: Magnesium ($Mg$)

• Functions

  • Provides bone rigidity ($60\%$ of body magnesium stored in bone).

  • Nerve/heart function and muscle relaxation.

  • Assists in over $300$ enzymatic reactions and glucose metabolism.

• Needs and Deficiency

  • RDA: $400$ to $420\,mg$ (Men); $310$ to $320\,mg$ (Women).

  • Deficiency: Irregular heartbeat, weakness, seizures. Caused by heavy perspiration, alcohol abuse, or diuretics.

  • UL: $350\,mg/day$ (nonfood sources). Excess causes diarrhea.

Trace Mineral: Iron ($Fe$)

• Functions

  • Hemoglobin: Transports oxygen and $CO_2$ in red blood cells.

  • Myoglobin: Oxygen storage in muscle cells.

  • Enzymes: Needed for brain/immune function and collagen synthesis.

• Iron Deficiency Anemia

  • Impact: Most common deficiency worldwide ($30\%$ of population).

  • Stages:

    • Stage 1: Depleted iron stores.

    • Stage 2: Depleted transferrin iron; physiological impairment begins.

    • Stage 3: Microcytic (small), hypochromic (pale) red blood cells; reduced oxygen capacity.

• Needs and Sources

  • RDA: $8\,mg$ (men/post-menopausal women); $18\,mg$ (women ages $18$ to $50$.

  • Heme Iron: Found in animal tissues (meat, fish, poultry); highly absorbable.

  • Nonheme Iron: Plant sources (beans, fortified grains); absorption increased by Vitamin C.

  • UL: $45\,mg/day$. Toxicity is a leading cause of poisoning in children. Hemochromatosis is a genetic disorder of excessive iron deposition.

Trace Mineral: Zinc ($Zn$)

• Functions

  • DNA synthesis, protein metabolism, and wound healing.

  • Development of reproductive organs.

  • Storage and function of insulin.

  • Antioxidant: Component of superoxide dismutase.

• Deficiency and Needs

  • Symptoms: Acne-like rash, hair loss, impaired taste/smell, delayed growth/puberty.

  • RDA: $11\,mg$ (men); $8\,mg$ (women).

  • UL: $40\,mg/day$. Excess zinc interferes with copper metabolism.

Trace Mineral: Selenium ($Se$)

• Functions

  • Antioxidant: Cofactor for glutathione peroxidase; spares Vitamin E.

  • Thyroid hormone activation.

• Status

  • Content in food depends strictly on soil content (e.g., China's Keshan province is low).

  • RDA: $55\,μg/day$; UL: $400\,μg/day$.

  • Toxicity signs: Hair loss, cirrhosis, nausea.

Trace Mineral: Iodine ($I$)

• Functions

  • Supports thyroid hormone synthesis with tyrosine.

  • Regulates metabolic rate and growth.

• Deficiency

  • Goiter: Enlarged thyroid gland attempting to trap more iodine.

  • Congenital Hypothyroidism: Occurs if deficiency happens during pregnancy.

  • History: Low-iodine soil in the Great Lakes region led to the iodization of salt.

  • RDA: $150\,μg/day$; UL: $1100\,μg/day$.

Trace Mineral: Copper ($Cu$)

• Functions

  • Ceruloplasmin: Protein that carries copper in the blood.

  • Involved in collagen cross-linking and neurotransmitter synthesis.

• Conditions

  • Menkes Syndrome: Genetic disease decreasing copper available to the brain.

  • Wilson’s Disease: Copper accumulates in liver and lungs due to inability to synthesize ceruloplasmin; treated with a vegan diet.

  • Source: Dark chocolate provides approximately $500\,μg$ per ounce.

Trace Mineral: Fluoride ($F$)

• Functions

  • Strengthens tooth structure and stimulates remineralization of enamel.

  • Provides antibacterial effects on plaque.

• Status

  • AI: $3.1\,mg$ to $3.8\,mg/day$.

  • Sources: Fluoridated water ($1\,\text{cup} = 0.25\,mg$, marine fish, tea.

  • Fluorosis: Mottling and pitting of teeth from excessive intake (often toothpaste swallowing in children).

Hypertension and the DASH Diet

• Parameters of Hypertension

  • Systolic: Top number ($< 120\,mm\,Hg$ is optimal).

  • Diastolic: Bottom number ($< 80\,mm\,Hg$ is optimal).

  • Risk Factors: Obesity (#1), inactivity (#2), alcohol (#3), high sodium (#4).

• DASH Eating Plan

  • High in: Calcium, Potassium, Magnesium, fruits, vegetables, and low-fat dairy.

  • Low in: Fat and sodium.

  • Effectiveness:

    • Lose $20\,lbs$: $-5\,points$ systolic.

    • Adopt DASH: $-11\,points$ systolic.

    • Limit Sodium: $-5$ to $-6\,points$ systolic.

    • Exercise: $-5$ to $-8\,points$ systolic.

• Daily Servings for DASH

  • Grains: $6$ to $8$ servings.

  • Fruits/Vegetables: $4$ to $5$ servings each.

  • Low-fat Dairy: $2$ to $3$ servings.

  • Meats/Fish: $≤ 2$ servings.

  • Nuts/Seeds/Legumes: $4$ to $5$ per week.

Farm to Fork: Agricultural Insights

• Bananas

  • Grown year-round in tropical climates.

  • Harvested green; ripen in $5$ to $7$ days at room temperature.

  • Cavendish is the common sweet yellow banana; Red bananas and Lady Fingers offer higher antioxidants.

• Onions and Garlic

  • Garlic: Plant one clove to grow a head with $16$ cloves. Rest chopped garlic for $10$ minutes to maximize allicin production.

  • Onions: Outer skin protects against mold and preserves juiciness.