Nutrition Science Fundamentals
Core concepts
Candidates must be fluent in macronutrient energy yields (carbohydrate 4 kcal/g, protein 4 kcal/g, fat 9 kcal/g, alcohol 7 kcal/g), the distinction between essential and conditionally essential amino acids, and the roles of fiber fractions (soluble versus insoluble) in glycemic and lipid control. Know the fat-soluble vitamins (A, D, E, K) and their absorption with dietary fat, water-soluble vitamin losses during cooking, and the major mineral functions: calcium and phosphorus in bone, iron in oxygen transport, zinc in wound healing and immunity, potassium in cardiac rhythm. Understand protein quality measures (PDCAAS, DIAAS), nitrogen balance, and the concept of biologic value. Grasp energy expenditure components: resting metabolic rate (roughly 60-70% of total), thermic effect of food, and activity thermogenesis.
Traps
Questions often test calorie arithmetic with alcohol or with fiber, which yields about 2 kcal/g rather than 4. Another trap is confusing fat-soluble vitamin toxicity risk with water-soluble vitamins, which are generally excreted. Watch for items that mislabel conditionally essential nutrients (glutamine, arginine, cysteine, taurine) as strictly essential. Also beware of questions that conflate DIAAS with PDCAAS scoring limits.
Worked example
A snack contains 20 g carbohydrate, 5 g protein, 10 g fat, and 5 g alcohol. Energy = (20x4) + (5x4) + (10x9) + (5x7) = 80 + 20 + 90 + 35 = 225 kcal. Rule of thumb: compute each macronutrient separately before summing, and never apply 4 kcal/g to alcohol or fat.