Glossary index

The Nutrition Reference Glossary

54 terms covering nutrition science, metabolic physiology, and the concepts behind modern dietary assessment. Each entry is reviewed against primary sources.

Dietary Assessment

• 24-Hour Dietary Recall A retrospective interview method in which a trained interviewer elicits everything consumed in the previous tw…
• Doubly Labelled Water The reference method for measuring total energy expenditure in free-living humans, using the differential elim…
• Food Frequency Questionnaire A retrospective instrument that asks how often each of a fixed list of foods was consumed over months or a yea…
• Weighed Food Record A prospective dietary assessment method in which every item consumed is weighed and recorded at the time of ea…

Metabolic Physiology

• Absorption Kinetics The time course of nutrient uptake from the intestinal lumen into circulation, characterized by rate constants…
• Gluconeogenesis The metabolic pathway that synthesizes glucose from non-carbohydrate substrates — lactate, glycerol, and gluco…
• Incretins Gut-derived hormones — principally GLP-1 and GIP — that augment glucose-dependent insulin secretion after oral…
• Ketogenesis The hepatic mitochondrial synthesis of ketone bodies — acetoacetate, beta-hydroxybutyrate, and acetone — from …
• Ketosis A metabolic state characterized by circulating ketone body concentrations above 0.5 mmol/L, reflecting hepatic…
• Muscle Protein Breakdown The catabolic process by which skeletal muscle proteins are degraded to free amino acids via autophagy-lysosom…
• Muscle Protein Synthesis The anabolic process by which amino acids are assembled into new skeletal muscle proteins, driven by mTORC1 si…
• Net Protein Balance The algebraic difference between protein synthesis and protein breakdown, expressed per unit time and determin…
• Postprandial Response The coordinated metabolic, hormonal, and hemodynamic changes following a meal, including glucose, lipid, amino…
• Protein Leverage Hypothesis The hypothesis that humans prioritize absolute protein intake over total energy intake, overeating fats and ca…
• Satiety Hormones A class of gastrointestinal peptide hormones — including CCK, PYY, GLP-1, and oxyntomodulin — released in resp…
• Short-Chain Fatty Acids Two- to six-carbon fatty acids produced by colonic bacterial fermentation of fermentable fiber, serving as col…
• Thermic Effect by Macronutrient The differential energy cost of digesting, absorbing, and assimilating each macronutrient — approximately 20-3…

Macronutrient Science

• Alpha-Linolenic Acid An essential omega-3 polyunsaturated fatty acid with 18 carbons and three double bonds, precursor to EPA and D…
• Amino Acids The organic building blocks that assemble into proteins and serve as precursors to neurotransmitters, hormones…
• BCAAs The three essential amino acids — leucine, isoleucine, and valine — whose aliphatic side chains share a common…
• Casein Protein The insoluble phosphoprotein fraction of milk that forms slowly digested micellar curds in the stomach, produc…
• DIAAS Score A protein quality metric that scores dietary protein by the ileal digestibility of each indispensable amino ac…
• Essential Amino Acids The nine amino acids the adult human body cannot synthesize de novo in adequate quantity and must obtain from …
• Fiber: Soluble vs Insoluble The traditional dichotomy of dietary fiber by water solubility, with soluble fibers tending to form viscous ge…
• Leucine A branched-chain essential amino acid that serves as the principal nutritional trigger of muscle protein synth…
• Linoleic Acid An essential omega-6 polyunsaturated fatty acid with 18 carbons and two double bonds, the parent compound from…
• Medium-Chain Triglycerides Triglycerides composed of medium-chain fatty acids (C6-C12) that are absorbed via portal circulation rather th…
• Monounsaturated Fats Fatty acids with exactly one carbon-carbon double bond, dominantly oleic acid (C18:1), characteristic of olive…
• PDCAAS Score A protein quality metric introduced by FAO/WHO in 1989 that scores proteins by amino acid composition correcte…
• Plant Protein Dietary protein derived from plant sources — legumes, grains, nuts, seeds — with amino acid profiles and diges…
• Polyunsaturated Fats Fatty acids containing two or more carbon-carbon double bonds, encompassing the omega-3 and omega-6 families a…
• Saturated Fats Fatty acids containing no carbon-carbon double bonds, typically solid at room temperature, found primarily in …
• Whey Protein The soluble protein fraction of milk, rich in essential amino acids and leucine, with rapid digestion kinetics…

Biochemistry

• Beta-Hydroxybutyrate The dominant circulating ketone body in fasting and ketogenic states, functioning as energy substrate, epigene…
• Gut Microbiome Diversity The richness and evenness of microbial taxa inhabiting the gastrointestinal tract, serving as a common biomark…
• Micronutrient Bioavailability The fraction of an ingested nutrient that is absorbed and made available for physiological function or storage…
• Phytates Plant-derived inositol hexaphosphate storage compounds that chelate dietary minerals in the intestinal lumen, …

Micronutrient Science

• Calcium The most abundant mineral in the human body, required for skeletal mineralization, neuromuscular function, blo…
• DHA A 22-carbon omega-3 polyunsaturated fatty acid concentrated in neural and retinal membranes, essential for nor…
• EPA A 20-carbon omega-3 polyunsaturated fatty acid and precursor to 3-series prostaglandins and E-series resolvins…
• Folate A water-soluble B vitamin essential for one-carbon transfer reactions including thymidylate synthesis, methion…
• Heme vs Non-Heme Iron The two dietary forms of iron with distinct absorption pathways — heme iron from animal-source foods with 15-3…
• Iodine An essential trace mineral required exclusively for thyroid hormone synthesis, with iodine deficiency historic…
• Iron An essential trace mineral required for hemoglobin, myoglobin, cytochromes, and numerous iron-sulfur cluster e…
• Magnesium An essential divalent cation cofactor for over 300 enzymatic reactions including ATP handling, DNA/RNA synthes…
• Omega-3 Fatty Acids A family of polyunsaturated fatty acids with the first double bond at the third carbon from the methyl end, in…
• Omega-6 Fatty Acids Polyunsaturated fatty acids with the first double bond at the sixth carbon from the methyl end, with linoleic …
• Potassium The principal intracellular cation, essential for resting membrane potential, cardiac and neural excitability,…
• Prebiotics Non-digestible food substrates that selectively promote the growth or activity of beneficial gut microorganism…
• Probiotics Live microorganisms that, when administered in adequate amounts, confer a health benefit on the host — typical…
• Sodium The principal extracellular cation, essential for fluid balance, nerve conduction, and active transport; consi…
• Vitamin B12 A cobalt-containing water-soluble vitamin essential for DNA synthesis, fatty acid metabolism, and myelin maint…
• Vitamin D A fat-soluble secosteroid essential for calcium and phosphate homeostasis, synthesized in skin from 7-dehydroc…
• Zinc An essential trace mineral and structural/catalytic cofactor for over 300 enzymes and more than 2000 transcrip…