Nutritional Science Fundamentals Flashcards

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?

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).

What type of dietary fiber is most associated with lowering LDL cholesterol by binding bile acids in the intestinal lumen?

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.

Which essential fatty acid serves as the precursor for eicosanoids with generally pro-inflammatory effects?

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.

What is the primary reason the NTA emphasizes consuming nutrient-dense, whole foods rather than relying on isolated supplements?

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.

Which of the following best describes the process of beta-oxidation?

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.

What is the significance of the omega-6 to omega-3 fatty acid ratio in the diet?

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.

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?

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.