NTA Nutritional Science Fundamentals 4 — Questions and Answers
Question 1: Which fat-soluble vitamin requires conversion to its active form 1,25-dihydroxyvitamin D3 (calcitriol) through a two-step hydroxylation process involving the liver and kidneys?
- Vitamin A
- Vitamin D (Correct answer)
- Vitamin E
- Vitamin K
Correct answer: Vitamin D
Vitamin D undergoes first hydroxylation in the liver to 25-hydroxyvitamin D and then a second hydroxylation in the kidneys to form the active hormone calcitriol (1,25-dihydroxyvitamin D3).
Question 2: What type of dietary fiber is most associated with lowering LDL cholesterol by binding bile acids in the intestinal lumen?
- Insoluble cellulose
- Soluble viscous fiber such as beta-glucan and pectin (Correct answer)
- Resistant starch
- Lignin
Correct answer: Soluble viscous fiber such as beta-glucan and pectin
Soluble viscous fibers like oat beta-glucan and pectin form a gel in the intestine that binds bile acids, forcing the liver to use cholesterol to synthesize new bile, thereby reducing LDL levels.
Question 3: Which essential fatty acid serves as the precursor for eicosanoids with generally pro-inflammatory effects?
- Alpha-linolenic acid (ALA)
- Eicosapentaenoic acid (EPA)
- Arachidonic acid (AA) (Correct answer)
- Docosahexaenoic acid (DHA)
Correct answer: Arachidonic acid (AA)
Arachidonic acid (AA), an omega-6 fatty acid, is the primary precursor for series-2 prostaglandins, thromboxanes, and series-4 leukotrienes, which tend to be pro-inflammatory.
Question 4: What is the primary reason the NTA emphasizes consuming nutrient-dense, whole foods rather than relying on isolated supplements?
- Supplements are always more expensive than whole foods
- Whole foods provide synergistic cofactors and phytonutrients that enhance nutrient bioavailability and utilization (Correct answer)
- Isolated nutrients are always harmful in supplement form
- Whole foods have lower caloric density than supplements
Correct answer: Whole foods provide synergistic cofactors and phytonutrients that enhance nutrient bioavailability and utilization
The NTA's whole-food philosophy recognizes that nutrients in food exist within a complex matrix of cofactors, phytonutrients, and enzymes that work synergistically to enhance absorption and utilization.
Question 5: Which of the following best describes the process of beta-oxidation?
- The synthesis of fatty acids from acetyl-CoA in the liver
- The sequential removal of two-carbon units from fatty acids to produce acetyl-CoA for energy (Correct answer)
- The conversion of glucose to pyruvate in the cytoplasm
- The oxidation of amino acids to produce ATP in the TCA cycle
Correct answer: The sequential removal of two-carbon units from fatty acids to produce acetyl-CoA for energy
Beta-oxidation is the catabolic process occurring in the mitochondria where fatty acids are repeatedly cleaved to yield two-carbon acetyl-CoA units that enter the TCA cycle for ATP production.
Question 6: What is the significance of the omega-6 to omega-3 fatty acid ratio in the diet?
- It determines the total fat content of the diet
- A high omega-6 to omega-3 ratio promotes pro-inflammatory eicosanoid production and is associated with chronic disease risk (Correct answer)
- Omega-6 fatty acids neutralize the effects of omega-3 fatty acids
- The ratio affects only cardiovascular risk with no other health implications
Correct answer: A high omega-6 to omega-3 ratio promotes pro-inflammatory eicosanoid production and is associated with chronic disease risk
When the omega-6 to omega-3 ratio is excessively high (modern Western diets average 15:1 to 20:1), arachidonic acid-derived pro-inflammatory eicosanoids dominate, contributing to chronic inflammation and disease.
Question 7: Which monosaccharide is primarily transported to the liver via the portal vein after absorption and is metabolized there rather than entering systemic circulation as glucose?
- Glucose
- Galactose and fructose (Correct answer)
- Mannose
- Ribose
Correct answer: Galactose and fructose
Fructose and galactose are taken up primarily by the liver via the portal vein, where they are converted to glucose, glycogen, or metabolized differently than glucose entering peripheral circulation.
NTA Nutritional Science Fundamentals 4
Which fat-soluble vitamin requires conversion to its active form 1,25-dihydroxyvitamin D3 (calcitriol) through a two-step hydroxylation process involving the liver and kidneys?