Human Nutrition Week 1 Summary

Food Choices

  • Influenced by habit, cultural heritage, preference, availability, social interaction, positive/negative associations.

Classes of Nutrients

  • Six classes: carbohydrates, lipids, proteins, vitamins, minerals, water.
  • Organic: carbohydrates, lipids, proteins, vitamins.
  • Inorganic: minerals, water.
  • Energy-yielding macronutrients: carbohydrates, lipids, proteins.
  • Micronutrients: vitamins, minerals.

Essential Nutrients

  • Carbohydrate: glucose units; dietary fibre.
  • Lipids: essential fatty acids \text{linoleic} and \alpha\text{-linolenic}.
  • Protein: 9 essential amino acids.
  • Vitamins: water-soluble (B(1), B(2), B(3), B(5), B(6), B({12}), biotin, folate, C); fat-soluble (A, D, E, K).
  • Minerals: major (Ca, Cl, Mg, P, K, Na, S); trace (Cr, Cu, F, I, Fe, Mn, Mo, Se, Zn).
  • Water is itself essential.

Energy in Nutrients

  • Carbohydrate: 4\,\text{kcal\,g}^{-1} = 17\,\text{kJ\,g}^{-1}
  • Protein: 4\,\text{kcal\,g}^{-1} = 17\,\text{kJ\,g}^{-1}
  • Fat: 9\,\text{kcal\,g}^{-1} = 37\,\text{kJ\,g}^{-1}
  • Alcohol (not a nutrient): 7\,\text{kcal\,g}^{-1} = 29\,\text{kJ\,g}^{-1}
  • Water: 0\,\text{kcal}

Energy Density

  • \text{Energy density}=\dfrac{\text{kJ}}{\text{g}}.
  • Lower-density foods (e.g., vegetables) allow larger portions for the same energy.

Function of Nutrients

  • Provide energy: carbohydrates, proteins, lipids.
  • Growth & development: proteins, lipids, vitamins, minerals, water.
  • Regulate body processes: proteins, lipids, vitamins, minerals, water.

Scientific Method

  • Observation → Hypothesis → Experiment → Results/Interpretation → Theory → New questions.

Research Designs & Evaluation

  • Epidemiological: cross-sectional, case-control, cohort.
  • Experimental: laboratory (animal/in vitro) and clinical trials.
  • Check reliability: peer-reviewed journal, author credentials/funding, adequate sample size, control group.

Nutrient Reference Values (NRVs)

  • EAR: meets 50\% of population.
  • RDI: meets 97\text{–}98\% of individuals.
  • AI: used when RDI cannot be set.
  • EER: energy intake predicted to maintain balance.
  • UL: highest safe average intake.
  • Apply to healthy people; based on average daily intake.

Acceptable Macronutrient Distribution Range (AMDR)

  • Carbohydrate: 45\text{–}65\% of energy.
  • Fat: 20\text{–}35\% of energy.
  • Protein: 15\text{–}25\% of energy.

Australian Dietary Guidelines & Food Groups

  • Maintain healthy weight; be physically active; choose amounts meeting energy needs.
  • Eat variety from: vegetables/legumes, fruit, wholegrain cereals, lean meats/alternatives, dairy/alternatives.
  • Limit saturated fat, added salt, added sugars, alcohol.
  • Encourage breastfeeding; store food safely.

Population Intake Snapshot

  • Average vegetables: 2.7 serves/day; <4\% meet \ge5 serves.
  • Average fruit: 1.5 serves/day; 31\% meet 2 serves.

Chronic Disease & Diet

  • Diet-related leading deaths: ischaemic heart disease, stroke, some cancers, diabetes.
  • Major contributors to disease burden (DALY): tobacco 9.0\%, high BMI 5.5\%, alcohol 5.1\%, physical inactivity 5.0\%, diets low in fruit 2.0\%, vegetables 1.1\%, wholegrains 1.1\%.

Nutrition Assessment

  • Individual: history, anthropometry, physical exam, lab tests.
  • Deficiency progression: primary/secondary cause → subclinical (covert) → clinical (overt).
  • Population surveys show rising intake of energy-dense foods and fast foods.

Identifying Nutrition Misinformation

  • Red flags: quick fixes, “natural”, miracle cures, personal testimonials, meaningless jargon, conspiracy claims.
  • Trust Accredited Practising Dietitians, Nutrition Australia, peer-reviewed research, Quackwatch.