Nutrition Science Fundamentals
Nutrition Science Fundamentals tests how nutrients are classified, how requirements are set, and how evidence is interpreted. Expect definitions, energy calculations, and distinctions among dietary reference intakes rather than isolated trivia.
Core rules
- Essential nutrients cannot be synthesized in adequate amounts and must come from the diet; conditionally essential nutrients become limiting in specific states.
- Energy factors are carbohydrate 4 kcal/g, protein 4 kcal/g, fat 9 kcal/g, and alcohol 7 kcal/g. Labels may use kJ; 1 kcal = 4.184 kJ.
- Dietary reference intakes include EAR, RDA, AI, UL, and AMDR. The RDA is set from the EAR and meets the needs of about 97.5% of healthy people; an AI is used when an EAR cannot be set; the UL is the highest usual intake likely to pose no adverse effect, not a toxicity threshold.
- Bioavailability depends on chemical form, food matrix, inhibitors, enhancers, and host factors.
Worked example
A meal provides 30 g protein, 50 g carbohydrate, and 20 g fat. Energy = (30 × 4) + (50 × 4) + (20 × 9) = 120 + 200 + 180 = 500 kcal. Protein supplies 120/500 = 24%, carbohydrate 40%, and fat 36%. If the person's target is 2,000 kcal, the meal supplies 25% of daily energy.
Traps
Do not compare a single food's nutrient content with an RDA as though the RDA were a minimum for every person. Do not treat AI and RDA as interchangeable. Do not use the UL to justify fear of ordinary foods; it applies to usual total intake. Keep gross energy separate from metabolizable energy.