Food and Nutrition Sciences
Macronutrients and energy
Digestion, absorption, and metabolism of carbohydrate, protein, and fat anchor this domain. Memorize Atwater factors: carbohydrate 4 kcal/g, protein 4 kcal/g, fat 9 kcal/g, alcohol 7 kcal/g. Questions often bait alcohol as 9 kcal/g or protein as 4.2-both wrong. Know that fiber yields little usable energy in humans, that a maintenance protein estimate is about 0.8 g/kg, and that needs rise with catabolic stress (roughly 1.2–1.5 g/kg).
Micronutrients and bioavailability
Fat-soluble vitamins (A, D, E, K) require bile and dietary fat, are stored in the body, and carry toxicity risk. Water-soluble vitamins are excreted more readily, but B12 requires intrinsic factor, and high folate intake can mask B12 deficiency. Heme iron is absorbed far better than non-heme iron; vitamin C enhances non-heme absorption, while phytates, oxalates, tannins, and calcium inhibit it.
Food science and safety
Distinguish Maillard browning (reducing sugar plus amino group, dry heat) from caramelization (sugar alone). Starch gelatinizes with heat and water; proteins denature and coagulate. Microbial growth depends on moisture (water activity), pH (C. botulinum will not grow below pH 4.6), temperature, time, oxygen, and nutrients. The temperature danger zone is 41–135°F.
Trap to expect
Freezing is bacteriostatic, not bactericidal-it halts growth but does not sterilize food, and thawed food can spoil as if never frozen.
Rule of thumb
To check energy quickly, multiply grams by the Atwater factor: a snack with 30 g carbohydrate, 10 g protein, and 5 g fat supplies 120 + 40 + 45 = 205 kcal.