Dietary requirements — the amounts of energy and specific nutrients needed each day — are not the same for everyone. They are influenced by physiological state, biological characteristics, and lifestyle factors. The Nutrient Reference Values (NRVs) for Australia and New Zealand, published by NHMRC, provide specific recommendations for different population groups.
KEY TAKEAWAY: There is no single dietary requirement that applies to everyone. Food choices must be tailored to the individual’s age, sex, life stage, and activity level.
EXAM TIP: Know the life stages that have the HIGHEST requirements for specific nutrients:
- Calcium: Adolescents and older adults
- Iron: Adolescent girls and pregnant women
- Folate: Women planning pregnancy and during first trimester
| Nutrient | Males | Females | Reason for Difference |
|---|---|---|---|
| Energy | Higher | Lower | Greater average body mass and muscle mass → higher BMR |
| Iron | 8 mg/day | 18 mg/day (19–50 yr) | Menstrual blood loss |
| Calcium | 1,000 mg | 1,000 mg (same in adulthood; higher in menopause) | Post-menopausal women at greater osteoporosis risk |
| Iodine | 150 µg | 150 µg | Same, but pregnancy increases to 220 µg |
Pregnancy dramatically increases nutrient requirements to support fetal development and maternal physiological changes:
| Nutrient | Why Increased | Recommendation |
|---|---|---|
| Folate | Neural tube development (first 4 weeks — often before pregnancy confirmed) | 600 µg/day + supplement 400 µg preconception |
| Iron | Fetal iron stores; increased red blood cell volume | 27 mg/day |
| Calcium | Fetal skeleton development | 1,000 mg/day |
| Iodine | Fetal brain and nervous system development | 220 µg/day |
| Vitamin D | Calcium absorption; fetal bone development | Maintain adequate status |
| Omega-3 (DHA) | Fetal brain and eye development | Oily fish 2–3 times/week |
| Energy | Increased metabolic demands; fetal growth | +1,400 kJ/day (2nd trimester); +1,900 kJ/day (3rd trimester) |
| Protein | Fetal tissue synthesis; placental development | Increased requirement |
Foods to avoid during pregnancy:
- Raw/undercooked meat and eggs (Salmonella, Listeria risk)
- Soft cheeses and pâté (Listeria)
- Raw seafood and smoked salmon (Listeria)
- High-mercury fish (shark, swordfish, orange roughy) — neural toxicity to fetus
- Alcohol (fetal alcohol spectrum disorder)
- Unpasteurised dairy
COMMON MISTAKE: Students sometimes say pregnancy has the highest energy requirements. Lactation actually requires more additional energy (+2,000 kJ) than pregnancy (+1,400–1,900 kJ).
Physical activity significantly influences energy requirements and, to a lesser extent, protein and carbohydrate needs:
| Activity Level | Description | Daily Energy Need (example adult female) |
|---|---|---|
| Sedentary | Desk job, minimal exercise | ~7,000–8,000 kJ/day |
| Lightly active | Light exercise 1–3 days/week | ~8,500–9,500 kJ/day |
| Moderately active | Moderate exercise 3–5 days/week | ~9,500–10,500 kJ/day |
| Very active | Vigorous exercise 6–7 days/week | ~11,000–12,500 kJ/day |
| Elite athlete | Intense daily training | 14,000+ kJ/day |
VCAA FOCUS: Be able to explain why a specific group needs more of a particular nutrient — the physiological reason. E.g., “Pregnant women need more folate because it is essential for neural tube development in the early weeks of pregnancy, when cell division is most rapid.”
