Chapter 8 — Water & Minerals

Water

  • Most indispensable nutrient; survival without water: only a few days
  • Body composition: 60\% of adult body weight
    • Present in arteries, veins, capillaries, cells, tissues, organs

Functions of Water

  • Transport vehicle for nutrients & wastes
  • Universal solvent
  • Body’s cleansing agent
  • Lubricant/cushion for joints
  • Protects sensitive tissues (e.g., eyes, spinal cord, fetus)
  • Maintains body temperature via sweat evaporation

Water Balance

  • Daily losses require equal intake (Fig. 8{-}2)
  • Thirst mechanism:
    • Blood too concentrated / volume or pressure too low → hypothalamus signals brain → thirst
    • Pituitary releases hormone → kidneys re-absorb water → decreased urine
    • Thirst sensation lags behind actual need
Dehydration (Table 8{-}1)
  • Progressive symptoms: thirst → weakness → exhaustion → delirium → death

Water Intake Recommendations

  • DRI provides \approx 80\% of total need from fluids
    • Males: 13 cups beverages
    • Females: 9 cups beverages
  • Remaining \approx 20\% from foods + metabolic water (from nutrient oxidation)
  • Requirements vary with diet, activity, temperature, humidity, altitude, etc. (Table 8{-}2)

Water Content of Foods (Table 8{-}3)

  • 100\%: plain water, diet soft drinks, plain tea, unflavoured seltzer
  • 99{-}95\%: sugar-free gelatin, clear broth, celery, cucumber, lettuce, Chinese cabbage, summer squash, decaf black coffee
  • 90{-}94\%: sports drinks (e.g., Gatorade), grapefruit, strawberries, broccoli, tomatoes
  • 80{-}89\%: soft drinks, milk, yogurt, egg white, fruit juice, low-fat cottage cheese, carrot, fresh apple

Types of Water

  • Hard water: high \text{Ca} & \text{Mg}
    • May protect against hypertension & heart disease
  • Soft water: high \text{Na}
    • May aggravate hypertension/heart disease; dissolves contaminants more easily

Water Safety

  • Universal solvent ⇒ potential contaminants: bacteria, viruses, heavy metals, organic chemicals, industrial spills
  • Public systems: disinfect (often chlorine) & test quality
  • Health Canada 🇨🇦 issues boil-water advisories when microbial/cloudiness hazards arise

Household & Commercial Options

  • Tap water: must meet federal/provincial standards
  • Home filters: remove lead, chlorine, some chemicals; do NOT remove chlorine-resistant microbes
  • Bottled water: federally regulated, variable mineral profile

Water Quality & Access — Indigenous Communities

  • Long-term advisories (>1 yr) widespread
  • Example: Neskantaga First Nation, Ontario — boil-water advisory since Feb 1995
  • Federal pledges to end advisories (Fig. 8{-}3); status questioned

Body Fluids & Minerals

  • Majority of body water = intracellular; remainder extracellular & in blood
  • Major minerals form salts ⇒ water follows salt
  • Cells actively pump salts to avoid collapse or swelling

Electrolytes

  • Compounds partially dissociate in water → ions
  • Unequal ion concentrations across permeable membrane → water shifts toward higher concentration

Fluid & Electrolyte Balance

  • Requires energy-dependent transport proteins (Na⁺ pumped out, K⁺ pumped in; Fig. 8{-}4 & 8{-}5)
  • Imbalances (vomiting, diarrhea, eating disorders) can be medical emergencies

Overview of Minerals

Major Minerals (≥100 mg/d requirement)

  • Calcium (Ca), Phosphorus (P), Potassium (K), Sulfur (S), Sodium (Na), Chloride (Cl), Magnesium (Mg)

Trace Minerals (<100 mg/d)

  • Iodine (I), Iron (Fe), Zinc (Zn), Copper (Cu), Selenium (Se), Fluoride (F), Chromium (Cr), Manganese (Mn), Molybdenum (Mo)

General Functions of Minerals

  • Electrolytes (Na, K, Cl): water & acid-base balance; muscle & nerve function
  • Body structure (Ca, P, Mg, F, Zn): bones & teeth
  • DNA/RNA/ATP/phospholipid structure: P
  • Protein structure: Fe (hemoglobin), I (thyroxine), Zn, Ca, Se
  • Cell signaling: Ca^{2+}, Na^{+}
  • Antioxidant enzymes: Zn, Cu, Mn, Se, S

Major Minerals Detail

Calcium

  • 1\% in body fluids, 99\% in bones/teeth (Fig. 8{-}6,8{-}7)
  • Fluid functions: ion transport, nerve transmission, blood pressure, heartbeat contraction, blood clotting, secretion, enzyme activation
  • Bone: structural matrix & Ca reservoir
  • DRI: 1,000 mg/d; UL: 2,500 mg/d (higher in youth)
  • Sources (Snapshot 8{-}1): milk/yogurt/cheese, sardines & salmon (bones), Ca-set tofu, leafy greens (absorption varies; Fig. 8{-}12)
  • Absorption: children 60\%, pregnancy 50\%, adults 25\%; ↑ when blood Ca low
  • Deficiency → osteoporosis; importance of achieving peak bone mass by late 20’s/early 30’s (Fig. C8{-}3; example Adults A vs B)

Phosphorus

  • Functions: acid-base buffer, DNA/RNA, energy metabolism, activates enzymes & vitamins, phospholipids, protein structure
  • DRI 700 mg/d; UL 4,000 mg/d
  • Stored mainly in bone & teeth
  • Deficiency rare (weakness, bone pain); excess → soft-tissue calcification (kidney)
  • Sources: dairy, canned fish, lean beef (Snapshot 8{-}2)

Magnesium

  • >50\% in bone; remainder in soft tissues & fluids
  • Roles: enzyme cofactor, energy release, metabolizes K/Ca/vit D, protein synthesis, muscle relaxation vs Ca contraction, tooth resistance to decay
  • DRI: males 400 mg/d, females 310 mg/d; UL 350 mg from supplements
  • Deficiency: weakness, confusion → muscle convulsions, hallucinations, swallowing difficulty, growth failure
  • Toxicity (non-food sources): diarrhea, dehydration, pH shift
  • Sources (Snapshot 8{-}3): legumes, cooked spinach, bran cereals, oysters, yogurt; processing removes Mg

Sodium

  • Principal extracellular cation; maintains fluid volume & acid-base, enables muscle & nerve function
  • 1 g salt ⇒ 400 mg Na (table salt 40\% Na by weight)
  • DRI 1,500 mg/d; UL 2,300 mg/d (≈5.6 g salt)
  • Canadians 6,000{-}8,500 mg/d (ages 19{-}30); males > females
  • Major sources (Table 8{-}7 & Fig. 8{-}9): processed meats, breads, pizza, poultry dishes, pasta, processed/non-legume dishes, processed foods
  • Excess → hypertension, ↑Ca excretion, heart/kidney stress, stomach cancer risk (Asian descent)
  • Reduction strategies: limit saltshaker (1 tsp ≈2,400 mg Na), choose unprocessed foods (higher K), read labels; front-of-package “high in sodium” ≥15\% DV (by 2026)

Potassium

  • Main intracellular cation; maintains fluid/elec balance, cell integrity, heartbeat
  • Sudden large loss (fasting, diarrhea, eating disorders, kwashiorkor) → heart failure
  • DRI 4,700 mg/d; typical Canadians meet ≈50\% (low produce intake)
  • Deficiency: muscle weakness, paralysis, confusion, heart failure; worsens hypertension, impairs glucose tolerance, ↑acidity, accelerates bone Ca loss, ↑kidney stones
  • Toxicity: weakness, vomiting; large oral dose may stop heart (infants esp. vulnerable); stomach usually triggers emesis
  • Best sources (Snapshot 8{-}4): fresh fruits, vegetables, legumes, whole foods

Chloride

  • Works with Na for fluid & acid-base balance; part of HCl in stomach → protein digestion
  • Sources: salt (added & natural)
  • DRI 2,300 mg/d; UL 3,600 mg/d; deficiency rare

Sulfate

  • Needed to synthesize sulfur-containing compounds (sulfur AAs) for skin, hair, nails
  • No DRI; deficiency not observed; excess (water) → diarrhea, colon damage

Trace Minerals Detail

Iodine

  • Constituent of thyroxine → regulates basal metabolic rate
  • DRI 150 µg/d; UL 1,100 µg/d
  • Sources: seafood, soil-dependent crops, iodized salt, milk (sanitizing iodine), bakery products
  • Deficiency: goitre, sluggishness, weight gain, cretinism in infants; major global cause of mental impairment
  • Toxicity: enlarged thyroid, poisoning

Iron

  • Part of hemoglobin & myoglobin → oxygen transport; energy metabolism
  • DRI: males 8 mg/d; females 18 mg/d; pregnancy 27 mg/d; UL 45 mg/d; vegetarians require 1.8\times DRI
  • Deficiency → iron-deficiency anemia (microcytic, hypochromic RBC; Fig. 8{-}10)
    • Physical: weakness, headaches, pallor, cold intolerance, pica
    • Mental: attention, learning, memory issues (Table 8{-}10)
  • Causes: malnutrition, parasites, chronic blood loss, shed cells/nails/hair; high-risk groups: >6 mo infants, children, teens, menstruating & pregnant individuals
  • Toxicity: limited absorption protects; hemochromatosis genetic overload → fatigue, depression, abdominal pain, tissue damage, liver failure; acute poisoning leading accidental death in <6 yr olds
  • Sources (Snapshot 8{-}5): meat, eggs, legumes, fortified cereal/bread/pasta, soy, broccoli, peas, dried fruits; cast-iron cookware non-food source
  • Absorption: heme \approx23\%; non-heme 2{-}20\%
    • Enhanced by \text{vit C}, MFP factor
    • Inhibited by tannins (tea/coffee), Ca & P (milk), phytates & fibre (whole grains)

Zinc

  • Works with every protein; enzyme cofactor for DNA/RNA, heme, pancreatic enzymes, macronutrient metabolism, vit A release
  • Regulates gene expression, behaviour, learning; immune, wound healing, sperm, taste, fetal development, visual pigments
  • DRI: males 11 mg/d; females 8 mg/d
  • Sources (Snapshot 8{-}6): meats, shellfish, poultry, dairy; plant sources (legumes, whole grains) less bioavailable (phytates)
  • Deficiency: diarrhea, impaired immunity, growth retardation
  • Toxicity: appetite loss, impaired immunity, death; blocks Cu & Fe absorption; pancreatic excretion helps regulate

Selenium

  • Antioxidant: part of enzymes preventing free-radical formation & activating thyroid hormone
  • Deficiency (rare) → higher risk prostate cancer, certain heart diseases
  • Sources: meats, shellfish, veg & grains from Se-rich soil

Fluoride

  • Not essential for life but prevents dental caries; strengthens developing & erupted teeth
  • Primary source: fluoridated tap water (just <40\% Canadians have access)
  • Excess → fluorosis (mottled enamel) via water, toothpaste, supplements

Chromium

  • Helps regulate blood glucose; deficiency mimics diabetes (↑blood glucose, impaired insulin/glucagon response)
  • Supplements ineffective for muscle building/fat loss/cholesterol lowering
  • Safe to 200 µg; recommended intake 50 µg/d; 90\% of adults consume less
  • Sources: unrefined foods, whole grains

Copper

  • Needed for hemoglobin & collagen synthesis; enzyme oxygen-handling; energy release
  • Deficiency: impaired growth/metabolism (infants), immunity & arterial function (adults)
  • UL 10,000 µg/d
  • Sources: organ meats, seafood, nuts, seeds

Controversy 8 – Osteoporosis

  • Definition: reduced bone mass → porous, fragile bones; fractures later in life but begins silently earlier

Bone Types

  • Cortical: dense outer shell & shaft
  • Trabecular: lattice interior, Ca bank
  • Bone loss timeline: trabecular mid-20s; cortical ≈40 yr
  • Consequences: vertebral compression & dowager’s hump, height loss, wrist/hip fractures, tooth loss

Diagnosis & Treatment

  • Assessment: DEXA X-ray or ultrasound; adults with family history screened ≥50 yr
  • Therapies: estrogen (↑ heart & breast cancer risk), meds e.g., Fosamax

Prevention

  • Diet: adequate Ca, vit D, other nutrients
  • Activity: weight-bearing exercise essential
  • Epidemiology (Osteoporosis Society of Canada):
    • >2.3 million Canadians ≥40 y with diagnosis
    • 80\% female
    • >80\% fractures ≥50 y due to osteoporosis
    • Economic burden: \$4.6 billion

Calcium Supplements

  • Forms:
    1. Calcium compounds (good absorption): carbonate, citrate, gluconate, hydroxylate, malate, lactate, phosphate, AA chelates
    2. Mixed with other compounds (poor): carbonate + Mg/aluminum (antacids), carbonate + vit D
    3. Powdered Ca-rich materials (poor): bone meal, oyster shell, dolomite
  • Elemental Ca varies: carbonate 40\%, glutamate 9\%
  • Absorbability test: dissolve in vinegar ≤30 min
  • Dosing: ≤500 mg elemental each time; take 2{-}3 smaller doses/day

Case Studies

Case 1

  • 50-y male, persistent diarrhea & nausea, dehydrated, flushed, heavy antacid (Mg-containing) use
  • Concern: magnesium toxicity (from antacids) → diarrhea, pH imbalance
  • Further risks: dehydration, electrolyte imbalance; monitor kidney function

Case 2

  • 23-y female lacto-vegetarian, fatigue, weakness, irritability, cold sensitivity, pale skin
  • Concern mineral: iron
  • Likely condition: iron-deficiency anemia
  • Dietary advice:
    • Increase iron-rich foods: legumes, eggs, dark greens, iron-fortified cereals, consider cast-iron cookware
    • Combine with vitamin C sources (citrus, peppers)
    • If ok with supplements, low-dose iron under guidance

Lucky Iron Fish Project

  • 2008, Cambodia, Carleton University
  • Cast-iron fish ingot symbolizes luck
  • Added to boiling water/soup to increase iron content, addressing deficiency