Food and Nutrition Science Knowledge
Macronutrients, energy, and standards
Energy conversion is the most-tested arithmetic: carbohydrate 4 kcal/g, protein 4, fat 9, alcohol 7, organic acids ~3. Fiber is not 4 kcal/g - fermentable fiber yields roughly 1.5–2 kcal/g, so mixed-meal items must be handled carefully. The Atwater system underlies most food-composition values.
Know how nutrient standards are built. The EAR is the median intake meeting the requirement of a healthy population; the RDA is set at EAR + 2 SD to cover ~97–98% of individuals; an AI is used when data are insufficient for an EAR and is not a requirement estimate; the UL is the highest average daily intake unlikely to cause adverse effects and is not a toxicity threshold. AMDRs give acceptable macronutrient ranges (e.g., 45–65% carbohydrate, 10–35% protein, 20–35% fat for adults).
Bioavailability distinctions appear constantly: heme vs non-heme iron (enhanced by vitamin C; inhibited by phytates, tannins, calcium); 1 mcg retinol activity equivalent = 12 mcg food beta-carotene = 24 mcg other provitamin-A carotenoids; 1 mcg vitamin D = 40 IU; 1 niacin equivalent = 60 mg tryptophan; folic acid is ~1.7 times as bioavailable as food folate.
Protein quality: PDCAAS uses fecal digestibility and truncates at 1.0; DIAAS uses ileal digestibility and can exceed 1.0; the limiting amino acid sets the score.
Metabolically, be able to trace fed (insulin-driven glycogen synthesis, lipogenesis) versus fasted (glucagon, glycogenolysis, gluconeogenesis, ketogenesis) states.
Rule of thumb (worked): 55 g carbohydrate, 25 g protein, 12 g fat = 220 + 100 + 108 = 428 kcal.