CDN Nutritional Science & Dietetics 4 — Questions and Answers
Question 1: Which phase of digestion is stimulated by the sight and smell of food before eating begins?
- Intestinal phase
- Gastric phase
- Cephalic phase (Correct answer)
- Absorptive phase
Correct answer: Cephalic phase
The cephalic phase is the neurally mediated response to food cues (sight, smell, taste) that prepares the GI tract by stimulating saliva and gastric secretions before food arrives.
Question 2: Pellagra is caused by deficiency of which vitamin, and what is its biochemical role?
- Thiamine; cofactor in pyruvate dehydrogenase
- Niacin; component of NAD+ and NADP+ for redox reactions (Correct answer)
- Riboflavin; component of FAD and FMN
- Biotin; cofactor for carboxylase enzymes
Correct answer: Niacin; component of NAD+ and NADP+ for redox reactions
Niacin deficiency causes pellagra (dermatitis, diarrhea, dementia, death); niacin forms NAD+ and NADP+, which are essential electron carriers in energy metabolism.
Question 3: What is the primary site of absorption for fat-soluble vitamins in the gastrointestinal tract?
- Stomach
- Jejunum (Correct answer)
- Terminal ileum
- Colon
Correct answer: Jejunum
Fat-soluble vitamins (A, D, E, K) are absorbed in the jejunum via micelle formation with bile salts, along with dietary fats.
Question 4: A dietitian is counseling an older adult on calcium intake. Which combination of factors most impairs calcium absorption?
- High vitamin D and low phytate intake
- Adequate stomach acid and sufficient vitamin D
- Low gastric acid (achlorhydria) and vitamin D deficiency (Correct answer)
- High dairy intake and normal kidney function
Correct answer: Low gastric acid (achlorhydria) and vitamin D deficiency
Calcium solubility and absorption requires adequate gastric acid and vitamin D (which induces calcium-binding proteins in intestinal cells); both are often deficient in older adults.
Question 5: Which hormone primarily inhibits appetite by signaling satiety to the hypothalamus after a meal?
- Ghrelin
- Cortisol
- Leptin (Correct answer)
- Neuropeptide Y
Correct answer: Leptin
Leptin, secreted by adipose tissue, signals the hypothalamus to suppress appetite and increase energy expenditure, reflecting long-term energy stores.
Question 6: In a patient with chronic kidney disease (CKD), which dietary modification is typically required to prevent hyperkalemia?
- Increase potassium-rich foods to support heart function
- Restrict dietary potassium to prevent dangerous elevations in serum levels (Correct answer)
- Supplement with potassium chloride salt substitutes
- Increase fruits and vegetables without restriction
Correct answer: Restrict dietary potassium to prevent dangerous elevations in serum levels
Impaired renal potassium excretion in CKD leads to hyperkalemia risk, so dietary potassium restriction is usually indicated to prevent cardiac arrhythmias.
Question 7: The Maillard reaction in food processing primarily affects which nutrients?
- Fats and water-soluble vitamins
- Proteins and carbohydrates, reducing lysine bioavailability (Correct answer)
- Minerals and fiber
- Cholesterol and saturated fats
Correct answer: Proteins and carbohydrates, reducing lysine bioavailability
The Maillard reaction between reducing sugars and amino acids (especially lysine) during heating creates browning compounds and reduces the bioavailability of lysine.
CDN Nutritional Science & Dietetics 4
Which phase of digestion is stimulated by the sight and smell of food before eating begins?