Glossary of Terms & Definitions
Listed Alphabetically - "C"
Cachexia: a state of ill health, malnutrition and wasting.
Calcification: the process of deposition of calcium salts, primarily hydroxyapatite. In the formation of bone this is a normal condition. In other organs, this could be an abnormal condition. Calcification of the aortic valve causes narrowing of the passage (aortic stenosis). Also called mineralization.
Calorie: a unit of heat. A calorie (cal) is the standard unit and the amount of heat necessary to raise 1 gram of water from 14 to 15 degrees C. The kilocalorie (kcal), used in metabolic and nutrition studies, is equal to 1000 calories.
Cancer: also known as malignancy, cancer refers to abnormal cells, which have a tendency to grow uncontrollably and metastasize or spread to other areas of the body. Cancer can involve any tissue of the body and can have many different forms in one tissue. Cancer is a group of more than one hundred different diseases.
Carbohydrate: considered a macronutrient because carbohydrates provide a significant source of calories (energy) in the diet. Chemically, carbohydrates are neutral compounds composed of carbon, hydrogen and oxygen. Carbohydrates come in simple forms known as sugars and such as starches and fiber.
Carboxylation: the introduction of a carboxyl group (-COOH) or carbon dioxide into a compound.
Carcinogen: a cancer-causing agent; adjective: carcinogenic.
Carcinogenesis: the formation of cancer cells from normal cells.
Carcinoid syndrome: the pattern of symptoms exhibited by individuals with carcinoid tumors. Carcinoid tumors secrete excessive amounts of the neurotransmitter, serotonin. Seratonin causes blood vessels to dilate (widen). Symptoms include flushing, diarrhea, and sometimes wheezing.
Cardiomyopathy: literally, disease of the heart muscle that often leads to abnormal function.
Cardiovascular: referring to the heart and blood vessels.
Cardiovascular diseases: literally, diseases affecting the heart and blood vessels. The term has come to encompass a number of conditions that result from atherosclerosis, including myocardial infarction (heart attack), congestive heart failure, and stroke.
Carnitine: a compound that is required to transport long chain fatty acids across the inner membrane of the mitochondria, in the form of acyl-carnitine, where they can be metabolized for energy.
Cartilage: a soft, elastic tissue that composes most of the skeleton of vertebrate embryos and except for a small number of structures is replaced by bone during ossification in the higher vertebrates. Cartilage cushions joints, connects muscles with bones, and makes up other parts of the body such as the larynx (voice box) and the outside portion of the ears.
Case-control study: a study in which the risk factors of people who have been diagnosed with a disease are compared with those without the disease. Because the risk factor (e.g., nutrient intake) is generally measured at the time of diagnosis, it is difficult to determine whether the risk factor was present prior to the development of the disease. Another potential draw back is the difficulty in obtaining well-matched control subjects.
Case reports: individual observations based on small numbers of subjects. This type of research cannot indicate causality but may indicate areas for further research.
Catalyze: increase the speed of a chemical reaction without being changed in the overall reaction process. See enzyme.
Catecholamines: substances with a specific chemical structure (a benzene ring with two adjacent hydroxyl groups and a side chain of ethylamine) that function as hormones or neurotransmitters. Examples include epinephrine, norepinephrine, and dopamine.
Cataract: clouding of the lens of the eye. As cataracts progress they can impair vision and may result in blindness.
Cation: a positively charged ion.
Celiac disease: also known as celiac sprue, celiac disease is an inherited disease in which the intestinal lining is inflamed in response to the ingestion of a protein known as gluten. Treatment of celiac disease involves the avoidance of gluten, which is present in many grains, including rye, oats, and barley. Inflammation and atrophy of the lining of the small intestine leads to impaired nutrient absorption.
Cell membrane: also called the plasma membrane. The external limiting membrane of a cell. It is composed of lipids (fat molecules) that have a hydrophobic (insoluble in water) end and a hydrophilic (water-soluble) end. Cell membranes are made of lipid bilayers in which the lipids line up in two layers with the hydrophobic ends facing each other and the hydrophilic ends facing the outside and the inside of the cell.
Cell signaling: communication among individual cells so as to coordinate their behavior to benefit the organism as a whole. Cell-signaling systems elucidated in animal cells include cell-surface and intracellular receptor proteins, protein kinases and protein phosphatases (enzymes that phosphorylate and dephosphorylate proteins), and GTP-binding proteins.
Central nervous system (CNS): the brain, spinal cord, and spinal nerves.
Cerebrospinal fluid: the fluid that bathes the brain and spinal chord.
Cerebrovascular disease: disease involving the blood vessels supplying the brain, including cerebrovascular accident (CVA), also known as a stroke.
Chelate: the combination of a metal with an organic molecule to form a ring-like structure known as a chelate. Chelation of a metal may inhibit or enhance its bioavailability.
Chemotherapy: literally, treatment with drugs. Commonly used to describe the systemic use of drugs to kill cancer cells, as a form of cancer treatment.
Cholesterol: a lipid used in the construction of cell membranes and as a precursor in the synthesis of steroid hormones. Dietary cholesterol is obtained from animal sources, but cholesterol is also synthesized by the liver. Cholesterol is carried in the blood by lipoproteins (e.g., LDL and HDL). In atherosclerosis, cholesterol accumulates in plaques on the walls of some arteries.
Cholestatic liver disease: liver disease resulting in the cessation of bile excretion. Cholestasis may occur in the liver, gall bladder or bile duct (duct connecting the gall bladder to the small intestine).
Cholinergic: resembling acetylcholine in action, a cholinergic drug for example. Cholinergic nerve fibers liberate or are activated by the neurotransmitter, acetylcholine.
Chorionic villus sampling (CVS): a procedure for obtaining a small sample of tissue from the placenta (chorionic villi) for the purpose of prenatal diagnosis of genetic disorders. CVS can be performed between 9 to 12 weeks of pregnancy.
Chromosome: a structures composed of a long DNA molecule and associated proteins that carries part of the hereditary information of an organism.
Chronic disease: an illness lasting a long time. By definition of the U.S. Center for Health Statistics, a chronic disease is a disease lasting 3 months or more.
Cirrhosis: a condition characterized by irreversible scarring of the liver, leading to abnormal liver function. Cirrhosis has a number of different causes, including chronic alcohol use and viral hepatitis B and C.
Citric acid cycle: A series of biological reactions that occurs in the matrix of mitochondria in which electrons are transferred to coenzymes and carbon dioxide is formed. The electrons carried by the coenzymes then enter the electron transport chain, which generates a large quantity of ATP. Also called the Krebs cycle.
Clinical trial: a research study, generally used to evaluate the effectiveness of a new treatment in human participants. Clinical trials are designed to answer specific scientific questions and to determine the efficacy of new treatments for specific diseases or health conditions.
Clone: an exact copy of a DNA segment; produced by recombinant DNA technology.
Coagulation: the process of involved in forming a blood clot
Coenzyme: a molecule that binds to an enzyme and is essential for its activity, but is not permanently altered by the reaction. Many coenzymes are derived from vitamins.
Cofactor: a compound that is essential for the activity of an enzyme.
Cognitive: an adjective referring to the processes of thinking, learning, perception, awareness, and judgment.
Cohort study: a study that follows a large group of people over a long period of time, often 10 years or more. In cohort studies, dietary information is gathered before disease occurs, rather than relying on recall after disease develops.
Collagen: a fibrous protein that is the basis for the structure of skin, tendon, bone, cartilage and all other connective tissue.
Collagenous matrix (of bone): The organic (nonmineral) structural element of bone. Collagen is a fibrous protein that provides the organic matrix upon which bone mineralize crystallizes.
Colon: sometimes called the large bowel or intestine, the colon is a long, coiled, tubelike organ that removes water from digested food after it has passed through the small intestine. The remaining material, solid waste called stool, moves through the colon to the rectum and leaves the body through the anus.
Colorectal adenoma: a tumor of the colon or rectum that arises in glandular tissue. Although not cancer, colorectal adenomas may develop into colorectal cancer over time.
Colorectal cancer: cancer of the colon (large intestine) or rectum.
Congenital hypothyroidism: also known as cretinism, congenital hypothyroidism occurs in two forms, although there is considerable overlap. The neurologic form is characterized by mental and physical retardation and deafness. It is the result of maternal iodine deficiency that affects the fetus before its own thyroid is functional. The myxedematous or hypothyroid form is characterized by short stature and mental retardation. In addition to iodine deficiency, the hypothyroid form has been associated with selenium deficiency and the presence of goitrogens in the diet that interfere with thyroid hormone production.
Congestive heart failure (CHF): a disorder of the heart, resulting in the loss of the ability to pump blood efficiently enough to meet the demands of the body. Symptoms may include swelling, shortness of breath, weakness, and exercise intolerance.
Cornea: the transparent covering of the front of the eye that transmits and focuses light into the eye.
Coronary artery: the vessels that supply oxygenated blood to the heart muscle itself, so named because they encircle the heart in the form of a crown.
Coronary artery bypass graft (CABG): a surgical procedure used in individuals with significant narrowings and blockages of coronary arteries to create new routes around narrowed and blocked arteries, permitting increased blood flow to the heart muscle. The bypass graft for a CABG can be a vein from the leg or an inner chest wall artery.
Coronary heart disease (CHD): also known as coronary artery disease and coronary disease, coronary heart disease is the result of atherosclerosis of the coronary arteries. Atherosclerosis may result in narrowing or blockage of the coronary arteries and is the underlying cause of myocardial infarction (heart attack).
Corticosteroid: any of the steroid hormones made by the cortex (outer layer) of the adrenal gland. Cortisol is a corticosteroid. A number of medications are analogs of natural corticosteroid hormones.
Creatine phosphate: a high-energy compound found in muscle cells which is used to convert ADP into ATP by donating phosphate molecules to the ADP. ATP is the molecule which is converted into ADP with a release of energy that the body then uses.
Crohn's disease: an inflammatory disease of the gastrointestinal tract, often affecting the small intestine and colon.
Cross-sectional study: a study of a group of people at one point in time to determine whether a risk factor or a level of a risk factor is associated with the occurrence of a disease. Because the disease outcome and the risk factor (e.g., nutrient intake) are measured at the same time, a cross-sectional study provides a "snapshot" view of their relationship. Cross-sectional studies cannot provide information about causality.
Cystic fibrosis (CF): a genetic (inherited) disease characterized by the production of abnormal secretions, leading to the accumulation of mucus in the lungs, pancreas, and intestine. This build-up of mucus causes difficulty breathing and recurrent lung infections, as well as problems with nutrient absorption due to problems in the pancreas and intestines. Without treatment, CF results in death for 95 percent of affected children before age five; however, the longest-lived CF patient survived into his late 30s.
Cytochrome P-450: an enzyme that plays an important role in the metabolism of drugs and toxins in the liver. It also plays a role in the synthesis (formation) of steroid hormones in the adrenal cortex.
Cytokine: a protein made by cells that affects the behavior of other cells. Cytokines act on specific cytokine receptors in the cells they affect.