Clinical Nutritionist CCN Gastrointestinal Health and Nutrition 1 — Questions and Answers
Question 1: Which probiotic strain has the most robust clinical evidence for preventing antibiotic-associated diarrhea?
- Lactobacillus acidophilus
- Bifidobacterium longum
- Lactobacillus rhamnosus GG (Correct answer)
- Streptococcus thermophilus
Correct answer: Lactobacillus rhamnosus GG
Lactobacillus rhamnosus GG has the strongest and most consistent evidence across clinical trials for reducing antibiotic-associated diarrhea.
Question 2: The primary site of vitamin B12 absorption in the gastrointestinal tract is the:
- Stomach
- Duodenum
- Terminal ileum (Correct answer)
- Jejunum
Correct answer: Terminal ileum
Vitamin B12 bound to intrinsic factor is absorbed exclusively in the terminal ileum via specific cubilin receptors.
Question 3: Which dietary fiber type has the strongest evidence for lowering LDL cholesterol?
- Insoluble fiber (cellulose)
- Soluble fiber (beta-glucan) (Correct answer)
- Resistant starch
- Lignin
Correct answer: Soluble fiber (beta-glucan)
Soluble fiber, particularly beta-glucan from oats, forms a viscous gel that binds bile acids and reduces LDL cholesterol through enterohepatic recycling.
Question 4: Increased intestinal permeability ('leaky gut') is primarily caused by dysregulation of:
- Mucus layer thickness
- Bile acid secretion
- Tight junction proteins (Correct answer)
- Brush border enzymes
Correct answer: Tight junction proteins
Leaky gut results from disruption of tight junction proteins (such as occludin and claudins) that normally seal the paracellular space between enterocytes.
Question 5: Short-chain fatty acids (SCFAs) produced by colonic fermentation of fiber primarily serve as the main energy source for:
- Liver hepatocytes
- Colonocytes (Correct answer)
- Small intestinal enterocytes
- Skeletal muscle cells
Correct answer: Colonocytes
SCFAs—especially butyrate—are the preferred fuel for colonocytes, providing approximately 70% of their energy needs.
Question 6: Celiac disease causes malabsorption primarily by:
- Excess mucus secretion blocking nutrient uptake
- Autoimmune destruction of intestinal villi triggered by gluten (Correct answer)
- Bacterial overgrowth in the small intestine
- Deficiency of pancreatic digestive enzymes
Correct answer: Autoimmune destruction of intestinal villi triggered by gluten
In celiac disease, gliadin peptides trigger an autoimmune response that destroys the intestinal villi, dramatically reducing absorptive surface area.
Question 7: By definition, a prebiotic must be:
- A live beneficial microorganism
- A non-digestible ingredient that selectively stimulates beneficial gut bacteria (Correct answer)
- An antimicrobial compound that eliminates pathogens
- A fermented dairy product containing live cultures
Correct answer: A non-digestible ingredient that selectively stimulates beneficial gut bacteria
Prebiotics are non-digestible food components that selectively feed and stimulate growth of beneficial bacteria, distinguishing them from probiotics (live organisms).
Clinical Nutritionist CCN Gastrointestinal Health and Nutrition 1
Which probiotic strain has the most robust clinical evidence for preventing antibiotic-associated diarrhea?