Absorption – The act of taking up or into by specific chemical or molecular action. In relation to digestion, this refers to the taking up of fluids and nutrients through cell walls into the body.
Adenosine Triphosphate (ATP) – The energy currency of life. It transports energy within cells for metabolism.
Amino Acid – A simple, biologically important compounds simple organic compound containing both a carboxyl (—COOH) and an amino (—NH2) group. Amino acids make up proteins when joined together.
- Essential – An amino acid that cannot be synthesised by the body, and must thus be consumed as part of the diet. There are 9 amino acids that are essential in the diet of humans: phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine.
- Conditionally Essential – An amino acid whose synthesis can be limited under special pathophysiological conditions, such as prematurity in an infant. There are 6 amino acids that are considered to be conditionally essential in humans: arginine, cysteine, glycine, glutamine, proline, and tyrosine.
- Non-essential – An amino acid that can be synthesised by the body, and is thus not essential as part of the diet. There are 5 amino acids that are considered to be non-essential in humans: alanine, aspartic acid, asparagine, glutamic acid and serine.
Anabolism – see Metabolism
Anaemia – See Deficiency.
Antioxidant – A substance that inhibits oxidation and removes damaging free radicals that have been shown to play a role in causing illness and disease.
Appetite – A desire for food or drink in order to satisfy a bodily craving.
Bacteria – Microscopic living organisms found in the environment.
Beriberi – See Deficiency.
Bile – An alkaline, yellowish fluid produced by the liver, and concentrated and stored in the gallbladder. It aids in the digestion, emulsification, and absorption of fats.
Bioavailability – The proportion of a nutrient or drug that enters the bloodstream when consumed, and is thus able to have an active effect in the body.
Bolus – A small, rounded mass of chewed food that travels from the mouth to the oesophagus through the action of swallowing
Carbohydrates – A large group of biological molecules that are made up of carbon, hydrogen, and oxygen atoms, with an empirical formula of Cm(H2O)n. Carbohydrates occur in foods and living tissues and include sugars, starch, and cellulose. They can be broken down to release energy in the body.
- Monosaccharide – The simplest carbohydrates (monomers) that cannot be hydrolyzed into smaller carbohydrate units. Examples include sugars such as glucose, fructose, and galactose.
- Disaccharide – Two monosaccharide units joined via a covalent bond known as a glycosidic linkage. Disaccharides are the simplest of all polysaccharides. Examples include sucrose, lactose, and maltose.
- Oligosaccharide – A carbohydrate polymer containing 3-9 monosaccharide units. Oligosaccharides have many functions in the body including cell recognition and cell binding. For example, glycolipids have an important role in cell recognition in the immune response.
- Polysaccharide – A carbohydrate polymer made up of more than 10 monosaccharide units. Their structure can range from linear to extensively branched. Their main function in living organisms is related to either structure or storage. Starch is a storage polysaccharide in plants, whilst glycogen is a storage polysaccharide in animals and humans.
Catabolism – See Metabolism
Cholesterol – A steroid alcohol found in animal fats and oils, bile, and other animal products. It is an important constituent of cell membranes and an important precursor of steroid hormones.
Chylomicron – A large lipid particle that is formed in the small intestine. It is responsible for the transport of dietary cholesterol and triglycerides into the bloodstream to bodily tissues.
Chyme – A thick, semifluid mass of partially digested food that exits the stomach and moves into the small intestine.
Coenzyme – Organic molecules that are required as ‘helpers’ for certain enzymes to perform their function.
Cortisol – See Hormone.
Defecation – The final step in the digestion process, in which waste material is eliminated from the body via the anus.
Deficiency – Shortage of a nutrient in the body due to inadequate intake or illness.
- Anaemia – Refers to a condition marked by a deficiency of red blood cells or haemoglobin in the blood, resulting in decreased transport of oxygen in the bloodstream. Various types exist. In relation to nutrition, anaemia is often linked to either vitamin B6 or vitamin B12 deficiency.
- Beriberi – Refers to a cluster of symptoms caused primarily by a nutritional deficiency of vitamin B1 (Thiamin).
- Night Blindness – Refers to a condition in which vitamin A deficiency results in the impairment of dark adaptation due to the failure of the retina to function properly.
- Pellagra – Refers to a deficiency disease caused by a lack of niacin or its precursor tryptophan in the diet. It is characterised by the 4 D’s: dermatitis, dementia, diarrhoea, and death.
- Rickets – Refers to defective mineralisation or calcification of bones in children due to a deficiency or impaired metabolism of vitamin D, calcium, or phosphorous. It can lead to fractures and deformed bone formation.
- Scurvy – Refers to a disease caused by vitamin C deficiency, which is characterised by swollen, bleeding gums and poor wound healing.
- Xeropthalmia – Refers to a condition in which vitamin A deficiency results in abnormal dryness of the conjunctiva and cornea of the eye, with inflammation and ridge formation.
Dietary Supplement – A product that is intended to supplement the intake of one or more nutrient component (vitamin, mineral, herb or other botanical, amino acid, metabolite, extract, or combination thereof) as a pill, capsule, tablet, or liquid.
Dietetics – A branch of science concerned with the application of nutritional principles and planning, the preparation of foods, and regulation of the diet in relation to both promoting health and preventing disease.
Dietitian – An expert in the field of dietetics. A dietitian is a regulated healthcare professional who is licensed to assess, diagnose, and treat nutritional problems. A dietitian meets a set of strict academic and professional requirements, including:
- Completion of a 4-year Bachelor Degree in Nutrition and Dietetics, or a 3-year Science Degree followed by a Master Degree in Nutrition and Dietetics.
- Satisfactory results on a registration exam.
- Practical experience in an approved health-care facility, foodservice organisation, and community healthcare setting.
Digestion – The process of making food absorbable by breaking it down into simpler chemical compounds in the body by mechanical and chemical means.
- Chemical Digestion –
- Mechanical Digestion –
DRI – Dietary Reference Intakes. The general term used for a set of reference values used to plan and assess nutrient intakes of normal, healthy individuals.
Duodenum – The first part of the small intestine that follows immediately after the stomach, and leads to the jejunum.
Elimination – The discharge of waste material from the body.
Emulsification – The breakdown of dietary fat globules in the duodenum into smaller droplets to provide a larger surface area on which the enzyme pancreatic lipase can act to digest fats into fatty acids and glycerol. Emulsification is assisted by the action of the bile.
Enrichment – The voluntary addition by a food manufacturer of one or more nutrient(s) to a food product with the sole purpose of adding nutritional value to the food. Differs from Fortification.
Enzyme – Any protein that acts as a catalyst to speed up biochemical reactions.
- Amylase – A group of enzymes that catalyses the breakdown of starch molecules.
- Cholesterol esterase – An enzyme that catalyses the hydrolytic cleavage of cholesterol into other sterols and triglycerides.
- Elastase – An enzyme that catalyses the digestion of elastic tissue.
- Enterokinase // Enteropeptidase – An enzyme that catalyses the conversion of trypsinogen to trypsin.
- Isomaltase // Dextrinase – An intestinal enzyme that catalyses the hydrolysis of isomaltose and dextrins.
- Lactase – An enzyme that catalyses the hydrolysis of lactose into 1 molecule of glucose + 1 molecule of galactose.
- Maltase – An enzyme that catalyses the hydrolysis of maltose into 2 molecules of glucose.
- Pepsin – An enzyme that makes up a large proportion of digestive juices found in the stomach. It released into the stomach as inactive pepsinogen, which is activated to form pepsin by the acidic pH of the stomach.
- Sucrase – An enzyme that catalyses the hydrolysis of sucrose into 1 molecule of glucose + 1 molecule of fructose.
Excretion – The act or process of discharging waste matter from the body.
Fasted State – The metabolic state of a person who hasn’t eaten for a period of time, characterised by a number of metabolic adjustments. In this state, the body starts to rely on endogenous sources of energy (glycogen, fat, protein), rather than exogenous sources of energy (food absorbed from the GIT).
Fatty Acid – A carboxylic acid with a long hydrophobic tail that is either saturated or unsaturated.
- Unsaturated – A fatty acid with a carbon chain that has one or more double bond.
- Saturated – A fatty acid with a carbon chain that has no double bonds.
- Trans – An unsaturated fatty acid produced by the partial hydrogenation of vegetable oils.
- Essential – Important fatty acids that humans need to consume in the diet due to the fact that the body is unable to synthesise them. These fatty acids are required for important bodily structures, functions, and processes.
- Short-chain Fatty Acid (SCFA) – A fatty acid made up of 2-6 carbons. Primarily absorbed through the portal vein and transported directly to organs.
Fed State – The metabolic state in the period following a meal, which is characterised by high levels of different nutrients in the bloodstream, including high levels of circulating blood glucose.
(Dietary) Fibre – The edible parts of plants or analogous carbohydrates that are resistant to digestion and absorption in the human small intestine with complete or partial fermentation in the large intestine. Dietary fiber includes polysaccharides, oligosaccharides, lignin, and associated plant substances. Dietary fibers have many beneficial physiological effects.
- Insoluble fibre – Fibre that does not dissolve in water, is metabolically inert and provides bulking. Insoluble fibre can act as a prebiotic and can be fermented in the large intestine. Bulking fibers are able to absorb water as they move through the digestive system, thus promoting good bowel function and easing defecation.
- Soluble fibre – Fibre that dissolves in water, is readily fermented in the colon, and can form a viscous mass in the GIT. Soluble fibre delays gastric emptying, which promotes satiety and an extended feeling of fullness.
Food – Any nutritious substance that people eat or drink in order to maintain life, maintenance, and growth.
Food-Based Dietary Guidelines – The South African Food-Based Dietary Guidelines are short, positive, science-based messages that aim to change the eating behaviour of the general population towards more optimal diets that meet energy and nutrient requirements, whilst simultaneously helping to protect against the development of noncommunicable diseases.
Fortification – The addition of one or more micronutrient(s) to a food product whether or not it was originally contained in the food for the purpose of preventing or correcting a demonstrated deficiency of one or more nutrient(s) in the general population or a specific population group within a country. Differs from Enrichment.
Free Radical – An atom or molecule that has a single unpaired electron that is able to cause oxidative damage to biological structures. Often associated with causing inflammation, disease, and illness.
Functional Food – Refers to whole foods and fortified, enriched, or enhanced foods that have potentially beneficial effects on health when consumed as pert of a varied diet on a regular basis, at effective levels. Includes:
- Convential foods with health benefits
- Modified foods (fortified, enriched, enhanced)
- Medical foods
- Foods for special dietary use
Gastrointestinal tract (GIT) – (also Digestive Tract) A long, continuous tube consisting of various organs through which food passes as it moves from the mouth to the anus.
Glucagon – See Hormone.
Hormone – A chemical substance produced in the body that controls and regulates the activity of certain cells or organs as part of the endocrine system.
- Cholecystokinin (CCK) – A hormone that is secreted in the duodenum in response to the presence of fats. It causes the contraction of the gallbladder, which releases bile, and the pancreas, which releases pancreatic enzymes.
- Cortisol – A steroid hormone that is produced in the adrenal gland, and is released in response to stress and low blood-glucose concentration. It functions to increase blood sugar, suppress the immune system, and aid in the metabolism of fat, protein, and carbohydrates.
- Epinephrine // Adrenaline – A hormone that is produced by the adrenal glands and certain neurons. It functions as part of the fight-or-flight response by increasing blood flow to muscles, cardiac output, pupil dilation, and blood-sugar levels.
- Gastrin – A hormone secreted by pyloric glands, which stimulates the secretion of gastric acid and pepsin in the stomach.
- Glucagon – A peptide hormone that functions to raise blood-glucose concentration. It has the opposite effect of insulin, playing a role in a negative feedback system that helps the body maintain stable blood-glucose levels.
- Glucagon-like Peptide-1 (GLP-1) – A hormone that stimulates the release of insulin and inhibits the release of glucagon. It delays the absorption of carbohydrates and contributes to satiety.
- Gastric Inhibitory Peptide (GIP) – A hormone that induces insulin secretion.
- Insulin – A peptide hormone produced in the pancreas, which functions to increase the uptake of glucose from the bloodstream into body cells and thus decrease blood-sugar levels.
- Oestrogen – The primary female sex hormone, which is responsible for the development and regulation of the female reproductive system and secondary sex characteristics.
- Progesterone – A hormone that is involved in the menstrual cycle, pregnancy, and embryogenesis in females.
- Secretin – A hormone that stimulates the secretion of pancreatic juices when chyme enters the small intestine.
- Somatostatin – A hormone that acts on acid-producing cells to reduce the secretion of gastrin, secretin, and histamine.
Hunger – A compelling need for food, often accompanied by the painful sensation or state of weakness due to the need.
Ingestion – The process of consuming a substance, normally by taking it in through the mouth into the gastrointestinal tract through eating or drinking.
Insoluble fibre – See (Dietary) Fibre.
Insulin – See Hormone.
Ketogenesis // Ketosis – A condition characterised by increased levels of ketone bodies in the body. The metabolic state in which most of the body’s energy supply comes from circulating ketone bodies.
Ketone Bodies – Three different water-soluble biochemical compounds that are produced as by-products when fatty acids are broken down for energy in the liver. They can be used by the heart and brain during periods of fasting and starvation in place of glucose.
Lipid – A group of organic compounds that includes fats, oils, sterols, waxes, fat-soluble vitamins, mono-/di-/triglycerides, phospholipids, and others.
Lipoprotein – A lipid-protein compound that allows fats to be transported in water both.
Malnutrition – Any condition that develops when the body doesn’t have the correct amount of nutrients.
- Overnutrition – Dietary imbalance due to excess intake.
- Undernutrition – Dietary imbalance due to inadequate intake, or excessive excretion, of essential nutrients.
Medium-Chain Fatty Acids – Fatty acids that have a hydrophobic tail made up of 6-12 carbon atoms. They are easily absorbed and metabolised by the body.
Metabolism – The sum of all chemical and physical processes by which the body breaks down and builds up molecules. Metabolism can either require or release energy, depending on the process.
- Anabolism – The process of making new, larger molecules from smaller ones with an input of energy. It is important for growth, maintenance, and synthesis of new body tissues.
- Catabolism – The breakdown of larger, more complex molecules into smaller, more basic ones, releasing energy in the process.
Micelle – A cluster of phospholipid molecules, which are dispersed by the action of bile salts, in the gut which plays a critical role in the transport of fats and fat-soluble compounds into small intestinal cells.
Microbiota – The ecological community of commensal, symbiotic and pathogenic microorganisms that literally share our body space. Our gut microbiota (also known as gut flora) is the name given to the microbial population living in our intestine.
Mineral – An inorganic substance that is needed in small amounts in the diet to maintain health and support physiological function.
- Major // macromineral – Required in the diet in amounts of > 100 mg/day (Ca, Mg, K, Na, S, P, Cl).
- Trace // micromineral – Required in the diet in amounts of < 100 mg/day (Zn, Fe, Cu, I, Se, Mn, Cr, F, Mb).
Motility – The spontaneous movement of food through the digestive system.
Mouth – The opening in the lower part of the human face, surrounded by the lips, through which food is taken in and from which speech and other sounds are emitted.
Night Blindness – See Deficiency.
Nutrient – A substance that provides nourishment essential for the maintenance of life, maintenance, and growth in a living organism.
- Macronutrient – Any nutrient that is required in relatively large amounts in the diet (carbohydrates, proteins, fats).
- Micronutrient – Any nutrient that is essential in the diet in small amounts to support normal physiological functions (vitamins, minerals).
- Essential – A nutrient that must be consumed as part of food or as a supplement due to the fact that it can’t be produced by the body in sufficient quantities or at all.
- Non-essential – A nutrient that is found in foods and has an impact on health, but does not need to be consumed as part of the diet due to the fact that the body is able to synthesise it in sufficient quantities.
Nutrient Density – The ratio comparing the proportion of nutrients in a food compared to the number of calories it provides. Nutrient dense foods, such as fruits, vegetables, and whole grains, provide more nutrients per calorie. “Empty calorie” foods, such as soft drinks, processed cerals, and sweets, provide minimal nutrients per calorie.
Nutrition – The science of food, its components, and how they are metabolised and used in the body for proper functioning and health.
Oestrogen – See Hormone.
Osteomalacia – The softening of bones caused by impaired bone metabolism.
Osteoporosis – A disease in which the loss of bone tissue, resulting in decreased bone strength, increases the risk of broken bones and fractures. Often as a result of hormonal changes, and/or a deficiency of calcium, phosphorous, or vitamin D.
Oxidative Stress – An imbalance between the production of free radicals and the ability of the body to counteract their effect through their neutralisation by antioxidants.
Peristalsis // Peristaltic Contractions – Wave-like muscular contractions of the GIT and other tubular structures that move their contents onwards.
Pellagra – See Deficiency.
Phytonutrient – Natural chemicals found in plants, which help protect them from germs, fungi, bugs, and other threats. As part of the human diet, phytonutrients aren’t essential for keeping you alive. However the consumption of phytonutrients has been linked to the prevention of disease and promotion of health.
Portion – How much of a food that you choose to eat at one time.
Prebiotic – Non-digestible, selectively fermented food ingredients that promote the growth of beneficial gut bacteria.
Probiotic – Beneficial, live bacteria that are often taken orally to supplement normal gut flora in the colon.
Progesterone – See Hormone.
Protein – A macronutrient that is made up of long sequences of amino acids. Proteins are critical for all biological structures and many physiological functions.
Protein quality – The ability of a protein to be absorbed into the body and achieve desired metabolic actions.
- Protein Efficiency Ratio (PER) – This method is based on the assessment of animal growth (weight gain) divided by the intake of a specific food. It is able to assess protein needed for growth, but not for maintenance.
- Net Protein Utilisation (NPU) – This is a ratio of the amino acids that are converted into useable body proteins to the ratio of amino acids supplied. This method of assessing protein quality is influenced by the amounts of essential amino acids found in the body and limiting amino acids in a food.
- Biological Value (BV) – This is a measure of the absorbed amino acids that are incorporated into body proteins and tissues. BV does not take into consideration how a food is digested and absorbed and can be influenced by dietary intake and the way in which a food is prepared.
- Protein Digestibility Corrected Amino Acid Score (PDCAAS) – In light of the practical difficulties associated with using each of the other methods described, the PDCAAS method has been adopted as the current internationally approved method for assessing protein quality. In the simplest of terms, this method of assessing protein quality takes into consideration the amino acid requirements of humans and their ability to digest protein in a food.
Rickets – See Deficiency.
Saliva – A watery mixture of secretions from salivary and mucosal glands that contains enzymes, alpha-amylase, organic salts, and mucin.
Scurvy – See Deficiency.
Secretion – The process of secreting/releasing a chemical substance by cells or glandular organs.
Serving Size – The amount of food or drink that is recommended to be served in at a time.
Soluble Fibre – See (Dietary) Fibre.
Sphincter – A ring of muscle surrounding an opening or tube. It functions to guard or close the opening, for example the anus or the openings of the stomach.
Triglyceride – A glyceride that is made up of a single glycerol molecule with three fatty acid chains attached via an ester bond.
- Medium-chain Triglycerides (MCTs) – Triglycerides with fatty acids that contain 6-12 carbons (e.g. palm kernel oil // coconut oil).
Vitamin – An organic nutrient that is required in very small amouts for growth and maintenance of good health.
- Fat-soluble – Vitamins A, D, E & K
- Water-soluble – Vitamin C & the B-vitamins
Xeropthalmia – See Deficiency.