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Nutrition and Health Part 1

Course Context & Lecture Objectives

  • Lecturer bridging earlier food-science content (chemistry, processing, safety, allergies) with human nutrition.
  • Audience includes dietetics students + others (arts, commerce, engineering, medicine).
  • 4 h module condensed from 2–3 full courses; will link Week 1 material to current topics.
  • Key aims:
    • Clarify the food–nutrient relationship in supplying nourishment and preventing disease.
    • Explain nutrient functions and the need for a diversified intake across Australia’s 5 food groups.
    • Introduce measurement tools (dietary, anthropometric, biochemical, clinical) that connect food choice to health outcomes.
    • Connect nutrition with chronic diseases: overweight/obesity, coronary heart disease (CHD), diabetes mellitus.

Recap of Prior Food-Science Topics

  • Composition of food: macronutrients, micronutrients, water.
  • Major food groups in Australia: 5 (fruit, vegetables/legumes, grains, lean meat/alternatives, dairy/alternatives).
  • Food chemistry & functional properties during processing.
  • Food preservation motives: seasonality surplus, safety, microbial control.
  • Food safety beyond microbes: allergies & intolerances (peanut allergy, pollen → hay fever, respiratory reactions, peanut anaphylaxis).

Nutrition Fundamentals: Food vs Nutrients

  • We eat food, not isolated nutrients; meals must combine food groups to supply nutrient mixtures.
  • Healthy diet = pattern that delivers adequate energy + essential nutrients, prevents deficiency & chronic disease.
  • Six classes of essential nutrients:
    1. Carbohydrates
    2. Proteins
    3. Lipids (fats & oils)
    4. Vitamins
    5. Minerals
    6. Water ➔ transport medium, digestion/absorption aid, ~60 % of body mass.

Criteria for Essentiality

  • Component must:
    • Perform a specific biological function (e.g., vitamin A → vision via rhodopsin).
    • Deficiency removal from diet causes identifiable signs/symptoms.
    • Re-addition reverses impairment and prevents permanent damage (e.g., citrus for scurvy).

Historical Milestones in Nutrition Science

  • 500–300 BC: Food considered "medicine or poison"; diet both cause & cure.
  • 1670 s: British physician uses iron filings in wine to treat chlorosis → identified as iron-deficiency anaemia.
  • 1747 (18th c): James Lind’s scurvy trial—lemons & oranges cured sailors; later linked to vitamin C.
  • 19th c developments:
    • Energy, protein, minerals regarded as sole essentials.
    • Beriberi in Japanese navy resolved with milk, meat, barley, unpolished rice ➔ discovery of thiamine (vitamin B₁).
  • Early 20th c:
    • Rickets in children initially mis-attributed to vitamin A; cod-liver oil (rich in fat-soluble vitamins) revealed need for vitamin D.
    • Discovery sequence of fat-soluble vitamins: A (earlier), D, E (1922; rat fertility study), K (1929; blood-clotting role).
  • 1960: Most essential nutrients catalogued; nutrition can now link nutrients to functions & disease prevention.

Key Deficiency Examples & Symptoms

  • Vitamin A: night-blindness (nyctalopia) ➔ video example; other sources—carrots, spinach.
  • Vitamin C: scurvy ➔ bleeding gums, failure of wound healing.
  • Thiamine (B₁): beriberi ➔ neuropathy, oedema.
  • Iron: anaemia ➔ pallor, fatigue.
  • Iodine: goitre; neurological deficits.

Biological Functions of Nutrients

  • Energy production ➔ mostly carbohydrates; fats & proteins sparingly.
  • Growth & development ➔ proteins (cell synthesis), lipids (cell membranes), iron & zinc, water-soluble vitamins (co-enzymes).
  • Regulation/maintenance ➔ vitamins & minerals as catalysts in metabolic pathways; water for transport & thermoregulation.

Malnutrition Spectrum (Double Burden)

  • Undernutrition: under-weight (low weight-for-age), stunting (low height-for-age), wasting (low weight-for-height), micronutrient deficiencies.
  • Overnutrition: overweight & obesity (≥ 10 % and ≥ 20 % above healthy weight range respectively).
  • WHO 2020–22 data:
    • 41\,\text{million} children <5 y overweight/obese.
    • 1.9\,\text{billion} adults overweight; 650\,\text{million} obese.
  • Both forms now coexist in every region—"double burden of malnutrition".

Obesity: Definition, Prevalence, Classification

  • World Obesity Federation (2017): chronic, relapsing, multifactorial disease characterised by excess adipose tissue that impairs health.
  • Body Mass Index (BMI) formula: \text{BMI}=\dfrac{\text{weight (kg)}}{\text{height (m)}^{2}}
    • <18.5 underweight; 18.5–24.9 normal; 25–29.9 pre-obese; ≥30 obese (Classes I–III subdivided at 35 and 40).
  • Australia: obesity rose from ≈20\% (1995) to 25\% (≈2018); overweight plateaued.

Health Consequences of Obesity

  • Reduced disease-free years; earlier onset of chronic illnesses.
  • Major comorbidities: type 2 diabetes, CHD, stroke, hypertension, certain cancers, asthma/COPD, gall-bladder disease, osteoarthritis.
  • Other impacts: sleep apnoea, breathing difficulty, joint pain, mobility limits, psychosocial stigma.
  • Multi-cohort European study (n ≈ 181 000): multiple chronic disease risk increases with BMI and smoking; excess adiposity amplifies mortality.

Assessment of Nutritional Status

1. Dietary Methods

  • Weighment Survey: weigh all foods/beverages for 3–7 days → highest accuracy.
  • 24-h Recall: interviewer records all intake of previous day using household measures; repeat recalls improve reliability; sensitive to under-reporting (ice-cream effect!).
  • Food-Frequency Questionnaire (FFQ): frequency & portion size of numerous foods over month/year; converts to nutrient estimates via software.
  • Food Diary/Record: real-time self-logged intake for 3 days+.
  • Tools: Australian Food Composition Database (AFCD) & FoodWorks convert foods → nutrient values.

2. Anthropometry

  • Basic: weight, height, circumferences (waist, hip, mid-upper arm).
  • Indices: BMI; Waist-to-Hip Ratio; growth charts (children).
  • Skinfold thickness (triceps, biceps, sub-scapular, supra-iliac) ➔ subcutaneous fat.
  • Bioelectrical Impedance Analysis (BIA): small current; resistance proportional to fat mass; also gives intra-/extra-cellular water.
  • Hydrostatic (Underwater) Weighing: uses Archimedes’ principle; body density ⇒ %body-fat (video demonstration).
  • Dual-energy X-ray Absorptiometry (DXA): bone mineral, lean mass, regional fat pattern (central vs peripheral).
  • Imaging (CT/MRI/NIR): visceral vs subcutaneous fat mapping; apple (central) vs pear (gluteo-femoral) distribution.

3. Biochemical/Laboratory Tests

  • Blood/urine assays for nutrient biomarkers (e.g., serum ferritin, plasma vitamin C, glucose, lipids).

4. Clinical Examination

  • Signs (visible to clinician): pallor, oedema, bleeding gums, skin lesions.
  • Symptoms (reported by patient): fatigue, night blindness, poor wound healing.

Australian Dietary Intake Snapshot

  • AIHW data (males & females):
    • Adequate fruit in young children (2–3 y); vegetables consistently inadequate across all ages.
    • Dairy acceptable in toddlers; grains high only in 70 y+ females (oats porridge popularity).
  • Low fibre intake linked to rising early-onset colorectal cancer (20s–40s cohort).

Dietary Fat & Carbohydrate Guidelines

  • WHO: limit total fat to 15–30\% of energy; SFA <10\%; trans-fat <1\%.
  • Recommended \text{PUFA} : \text{SFA} \approx 2:1; inclusion of MUFA (olive, canola) for 1:1:1 balance.
  • Watch discretionary foods high in refined carbs (biscuits, fries, sugary beverages).
  • Added sugars guideline: <10\% of total energy (preferably <5\%).

Physical Activity Recommendations

  • Adults: ≥60\text{ min} moderate-intensity (brisk walking) daily; target weekly energy expenditure \approx 11\,000\,\text{kJ}; ≥10\,000 steps/day.
  • Children (5–17 y): ≥60\text{ min} moderate-to-vigorous activity daily; <$2$ h recreational screen time.
  • Physical activity complements dietary management for weight control and metabolic health.

Treatment Hierarchy for Obesity

  1. Behavioural & lifestyle modification (dietary education, activity plans, cognitive-behavioural therapy).
  2. Pharmacotherapy (anti-obesity drugs when behavioural change insufficient).
  3. Bariatric surgery (gastric banding, sleeve, bypass) for severe cases—restricts stomach capacity.

Ethical, Practical & Policy Considerations

  • Evidence-based policy development essential (to be discussed Thursday): dietary guidelines, fortification, labelling.
  • Equity: double burden of malnutrition demands strategies that address both under- & overnutrition within the same population.
  • Environmental & socioeconomic drivers: food availability, marketing, sedentary work/lifestyles.

Next Lecture Preview

  • Digestion & absorption pathways for major nutrients.
  • Australian Dietary Guidelines plate model & serving sizes.
  • Real-world footage of micronutrient deficiency presentations.
  • Critical appraisal of nutrition policies and their scientific underpinnings.