Comprehensive Study Notes – Macronutrients, Micronutrients, Water & Minerals

Carbohydrates (CHO)

• Chemical nature & basic facts

  • Composed of carbon, hydrogen, oxygen.
  • Energy-yield: $4\ \text{cal\,g}^{-1}$.
  • Minimum cerebral requirement: $100\ \text{g\,day}^{-1}$ glucose.
  • Should supply ≥ 55 % of total caloric intake (acceptable range in guidelines: 45 % – 65 %).

• Classification

  • Monosaccharides: glucose, fructose, galactose.
  • Disaccharides: sucrose, lactose, maltose.
  • Polysaccharides: starch, glycogen (storage), dietary fibre.

• Types

  • Simple CHO
  • Rapidly digested; directly (glucose) or indirectly (other simple sugars) raise blood glucose.
  • Natural sources: fruit (fructose), milk (lactose).
  • Refined: table sugar (sucrose).
  • Surplus → glycogen (muscle & liver) or body fat.
  • Complex CHO (starch & fibre)
  • Polymers of glucose; require enzymatic digestion → slower glycemic rise → more sustained energy.
  • Food sources: breads, cereals, pasta, legumes, potatoes.

• Dietary fibre

  • Soluble (oat bran, beans, apples, carrots) → forms viscous gel, binds waste → lowers cholesterol & glycemic spike.
  • Insoluble (whole grains, fruit/veg skins & seeds) → absorbs water, increases bulk, accelerates transit.
  • Adequate Intake: $25\ \text{g\,day}^{-1}$ (women); $38\ \text{g\,day}^{-1}$ (men).

• Glycemic response / index

  • Depends on intrinsic GI value × CHO quantity; practical prediction is difficult due to numerous variables (food matrix, preparation, mixed meals, individual metabolism).

• Physiological roles

  • Immediate energy, protein-sparing, prevention of ketosis, substrate for glycogen & non-essential amino acids, precursor of specific body compounds.

Proteins

• Basic chemistry & energy

  • C, H, O, N (distinguishing element).
  • Yield: $4\ \text{cal\,g}^{-1}$.
  • 20 amino acids → 9 essential (isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, valine, histidine essential in infants).
  • Body cannot store extra amino acids → daily supply required.

• Dietary allowance & sources

  • RDA adults: $0.75\ \text{g kg}^{-1}\,\text{day}^{-1}$ (≈ $0.8\ \text{g kg}^{-1}$ in most references).
  • Highest biological value: animal proteins (meat, fish, eggs, milk).
  • Complementary plant combos (e.g.
    rice +methionine rich, beans +lysine rich) → complete AA profile.

• Key functions

  • Structure (skeletal muscle ≈ 40 %, skin ≈ 15 %, blood ≈ 15 %).
  • Enzymes, hormones (insulin, thyroxine, epinephrine), neurotransmitters, antibodies.
  • Fluid balance (albumin), acid–base buffering (COOH / NH₂ groups), transport (hemoglobin, lipoproteins, albumin).
  • Specialized compounds: opsin (vision), thrombin (clotting), melanin, niacin (from tryptophan).
  • Backup energy when CHO & fat inadequate.

• Protein synthesis concepts

  • Turnover: continuous degradation & resynthesis; rate varies (GI cells 2–3 d, RBC 60–90 d).
  • Metabolic pool: circulating free AAs (dietary + recycled).
  • Nitrogen balance
  • Intake $=\frac{\text{protein (g)}}{6.25}$ (protein is 16 % N).
  • Excretion ≈ urinary urea N +4 g (faeces, skin, hair).
  • Balance states: neutral (healthy adult), positive (growth, pregnancy, recovery), negative (starvation, trauma).

• Deficiency (PEM)

  • Marasmus: chronic kcal ± protein loss → severe wasting.
  • Kwashiorkor: acute protein lack with kcal adequacy → edema, fatty liver.
  • High prevalence in < 5 y developing world; in industrial nations secondary to chronic disease, alcoholism, anorexia, elderly.

• Excess & risks

  • ↑ urinary calcium → osteoporosis risk; ↑ homocysteine → endothelial damage/atherosclerosis.

• Vegetarian patterns

  • Vegan, lacto-ovo, lacto-, ovo-, flexitarian.
  • Well-planned diets meet protein RDA; nutrients of concern: vitamin B₁₂, iron, zinc, Ca, vitamin D, ω-3, iodine.

Fats (Lipids)

• Energy density & classes

  • $9\ \text{cal\,g}^{-1}$ ( > 2×CHO/protein).
  • Lipid classes: triglycerides (≈ 98 % food fat), phospholipids (lecithin), sterols (cholesterol).

• Fatty-acid types

  • Saturated (SFA): max H, solid @ RT (butter, lard, tropical oils) → ↑ LDL.
  • Unsaturated
  • Monounsaturated (MUFA): 1 double bond (olive, canola, peanut, avocado, nuts) → neutral/beneficial on lipids.
  • Polyunsaturated (PUFA): ≥ 2 double bonds.
    • ω-6 (linoleic) sources: soybean, corn, sunflower, safflower, nuts.
    • ω-3 (α-linolenic → EPA → DHA) sources: flax, walnuts, fatty fish (salmon, mackerel, sardine, tuna) → anti-inflammatory, CV benefit, neuro-development.
  • Trans fats: hydrogenated; behave like SFA → ↑ LDL, ↓ HDL; found in deep-fried & processed foods.

• Cholesterol

  • Endogenous synthesis (liver) → non-essential nutrient.
  • Functions: membranes, vitamin D, steroid hormones, bile acids.
  • Transport forms: LDL “bad”, HDL “good”.
  • Lifestyle: exercise ↑ HDL; low-SFA diet ↓ LDL.

• Physiological roles

  • Resting fuel (~ 60 % energy at rest).
  • Insulation, organ cushioning, temperature regulation.
  • Vehicle for vitamins A D E K absorption.
  • Specific FA roles:
  • SFA – membrane integrity.
  • MUFA – myelin structure.
  • EFAs – skin integrity, growth, eicosanoid synthesis (EPA > arachidonic acid for CV health).

• Metabolism

  • Catabolism: triglyceride → glycerol + FA via lipoprotein-lipase; ↑ when CHO inadequate → ketone formation; uncontrolled → ketosis/acidosis.
  • Anabolism: FA + glycerol → triglyceride; stored in adipocytes (virtually limitless, 1 lb fat ≈ 3500 cal).

• Dietary recommendations

  • Total fat AMDR $20\%\text{–}35\%$ kcals.
  • PUFA < 10 %, SFA + trans < 10 %, rest MUFA.
  • Average US intake ≈ 34 % kcal (men 95 g d⁻¹, women 67 g d⁻¹).

• Fat in foods (culinary functions)

  • Flavour carrier, heat transfer (frying), texture (flakiness, mouth-feel), moisture, delays staling.

• Deficiency risks: low-fat diets in infants/children, fat-malabsorption, lipid-free TPN → growth failure, dermatitis, reproductive & organ issues.

Vitamins

• General characteristics

  • Organic, individual molecules; required in $\mu\text{g}$–mg amounts → micronutrients.
  • Provide no energy but facilitate metabolic pathways.
  • Most cannot be synthesized (exceptions: D with sunlight, niacin from tryptophan, A from β-carotene).
  • Susceptible to heat/light/oxidation; losses differ among vitamins.

• Solubility groups

  • Fat-soluble: A, D, E, K (stored; risk of toxicity).
  • Water-soluble: C + B-complex (limited storage, except B₁₂; excess excreted).

• Key water-soluble vitamins

  • B₁ (Thiamin): CHO metabolism; deficiency → beriberi (wet = edema, dry = wasting). Alcoholism major risk.
  • B₂ (Riboflavin): coenzyme in energy metabolism; deficiency → cheilosis, glossitis, dermatitis, anemia; light-sensitive (milk in opaque carton).
  • B₃ (Niacin): nicotinic acid ↔ nicotinamide; deficiency → pellagra (dermatitis, diarrhea, dementia, death); therapeutic high-dose (1–6 g d⁻¹) lowers LDL but causes flushing; risk of hepatotoxicity/gout.
  • B₆ (Pyridoxine): AA metabolism, RBC formation; deficiency rare except alcoholism, isoniazid therapy.
  • Folate (B₉): DNA synthesis, homocysteine ↓; deficiency → macrocytic anemia, neural-tube defects; women of child-bearing age need $400\ \mu\text{g}$ synthetic folic acid + diet; excess may mask B₁₂ deficiency.
  • B₁₂ (Cobalamin): activates folate, myelin maintenance; needs intrinsic factor & gastric acid for absorption; deficiency (often due to pernicious anemia, atrophic gastritis) → neurologic damage + macrocytic anemia; only in animal foods; vegans need supplement.
  • Pantothenic acid & Biotin: coenzymes in TCA cycle, FA synthesis; widespread, rare deficiency.
  • Vitamin C (Ascorbic acid): collagen synthesis, antioxidant, enhances Fe absorption, immune support; deficiency → scurvy; ↑ requirement by +35 mg d⁻¹ for smokers.

• Antioxidant vitamins: C, E, β-carotene → scavenge free radicals; whole-food matrix > isolated megadoses (research ongoing).

• Food additives & pharmacologic use

  • Enrichment (B-vits in flour), fortification (vit D milk), preservatives (ascorbate).
  • Drug-like doses: niacin (lipids), tretinoin (acne, leukemia), high-dose C (wound healing).

• Supplement considerations

  • Use patterns: higher in non-Hispanic whites, elderly, educated; lowest in obese.
  • Populations benefiting: < 1200 kcal dieters, vegans (B₁₂, D), picky eaters, > 51 y, alcoholics, food-insecure, chronic illness meds.
  • Choose multivitamin ≤ 100 % DV; pills supplement but do not replace varied diet.

• Phytochemicals

  • Non-nutritive plant chemicals (color, aroma, defence) with health benefits (antioxidant, immune modulation, hormone regulation, antibacterial).
  • Hundreds identified; best obtained via variety of fruits, veg, whole grains, legumes, nuts.
  • Daily goal: ≥ 5 colorful produce servings; use cooking/storage practices that conserve vitamins.

Water

• Body content & compartments

  • ≈ 60 % TBW; distribution ≈ 2/3 intracellular, 1/3 extracellular.
  • Muscle ~ 70 % water, adipose ~ 25 %. Males > females (↑ lean mass).

• Physiological functions

  • Cell shape, temperature regulation (high specific heat + evaporative cooling), digestion & absorption (7–9 L GI secretions reabsorbed), transport medium (blood ≈ 92 % water), solvent, metabolic reactant, waste removal, lubrication & cushioning (joints, organs, mucus).

• Water balance

  • Output: insensible (skin, lungs) + sensible (urine ≥ 500 mL to excrete wastes, feces). Avg total loss 1750–3000 mL.
  • Intake: fluids (~ 80 %), foods (~ 20 %), metabolic water (≈ 250–350 mL).
  • Adequate Intake: Men $3.7\ \text{L day}^{-1}$ (≈ 3 L fluids); Women $2.7\ \text{L day}^{-1}$ (≈ 2.2 L fluids).
  • “8 × 8” rule (eight 8-oz glasses) is heuristic—not evidence based—for healthy adults with free access to water.

• Dehydration

  • 1–2 % body-weight loss → thirst, fatigue; 7–10 % → dizziness, collapse; left untreated → death. High-risk: vomiting, diarrhea, fever, burns, uncontrolled diabetes, high altitude/exercise.

• Over-hydration (Hyponatremia)

  • At-risk: infants, psychiatric polydipsia, post-surgery, endurance athletes; symptoms: lung congestion, confusion, seizures → coma.

Minerals & Electrolytes

• General

  • Inorganic elements from earth; retain chemical identity; not destroyed by heat/light; lost mainly by leaching.
  • Structural roles (bones, teeth) & regulators (fluid balance, acid–base, nerve transmission, muscle contraction, cofactors).

• Major minerals (macrominerals)

  • Calcium, phosphorus, magnesium, sodium, potassium, chloride, sulfur.

• Trace minerals (microminerals)

  • Iron, zinc, iodine, copper, manganese, fluoride, etc.
  • Narrow safe range—both deficiency & excess harmful; routine mega-dosing discouraged.

• Key electrolytes

  • Sodium (Na⁺): primary extracellular cation; fluid balance, nerve impulse.
  • High intake → ↑ BP; tips to lower (see list below).
  • Potassium (K⁺): major intracellular cation; blunts Na-induced BP rise.
  • Chloride (Cl⁻): extracellular anion; acid-base, gastric HCl.

• Practical sodium-reduction strategies

  • Limit processed & convenience foods (boxed mixes, frozen dinners, canned soups).
  • Cook at home; choose fresh/frozen veg; rinse canned veg; pick low-Na tuna & chicken; swap cured meats for rotisserie chicken; use herbs/acid instead of salt; buy no-salt cereals; low-Na condiments; DIY dressings; drain & rinse canned beans; moderate cheese; avoid salty snacks.

Quick Reference Equations & Numbers

• Energy values:
  • CHO $4\ \text{cal\,g}^{-1}$
  • Protein $4\ \text{cal\,g}^{-1}$
  • Fat $9\ \text{cal\,g}^{-1}$
• Nitrogen intake: $\text{g N} = \dfrac{\text{protein (g)}}{6.25}$
• 1 lb fat ≈ $3500\ \text{cal}$
• AMDR:
  • CHO $45\text{–}65\%$ kcal
  • Protein $10\text{–}35\%$ kcal
  • Fat $20\text{–}35\%$ kcal (SFA + trans < 10 %).

High-Yield Study Connections & Implications

• Protein-sparing role of CHO critical in trauma/illness—adequate CHO prevents muscle breakdown.
• Ketosis link: very-low-CHO diets, uncontrolled diabetes → ↑ fat catabolism & ketone formation → acid–base imbalance.
• Omega-3 FA eicosanoids anti-arrhythmic vs arachidonic acid (ω-6) pro-inflammatory—dietary balance matters.
• Folate fortification (1998) → ↓ neural-tube defects; showcases public-health nutrient intervention.
• Sodium-potassium ratio more predictive of BP than Na alone—emphasize fruits/veg + low-Na processed foods.
• Albumin & edema—clinical marker of protein status & fluid balance.
• Intrinsic factor & B₁₂—gastric surgery patients need lifelong injections/supplement.

Rapid Food & Lifestyle Tips

• ≥ 5 colorful fruit/veg servings day⁻¹ (vitamins, minerals, phytochemicals).
• Combine legumes + grains for complete plant protein.
• Swap SFA/trans fats for MUFA/PUFA (olive oil, nuts, fatty fish).
• Hydrate intuitively; monitor pale-yellow urine; increase fluids in heat/exercise/illness.
• Choose whole, minimally processed foods to naturally moderate sodium, added sugars, and unhealthy fats.