Health Glossary - A to Z

[Tim Wescott]

"A"

Absorption: The taking up of liquids by solids or of gases by solids; intake of fluid or other substances by cells of the skin or mucous membranes; the passage of digested foods from the gastrointestinal tract into blood or lymph.

Acetylation: the addition of an acetyl group (-COCH3) group to a molecule.

Acetylcholine: A neurotransmitter liberated by peripheral nervous system neurons and some central nervous system neurons. It is excitatory at neuromuscular junctions but inhibitory at some other synapses.

Acidic: having a pH of less than 7.

Acute: having a rapid onset, short and relatively severe course; not chronic.

Adjunct: assisting in the prevention, amelioration, or cure of a disease.

Adrenal glands: a pair of small glands, located above the kidneys, consisting of an outer cortex and inner medulla. The adrenal cortex secretes cortisone-related hormones and the adrenal medulla secretes epinephrine (adrenaline) and norepinephrine (noradrenaline).

AI: adequate intake. A recommended intake value based on observed or experimentally determined approximations or estimates of nutrient intake by a group of healthy people that are assumed to be adequate, The AI is used when the RDA cannot be determined.

AIDS: acquired immune deficiency syndrome. AIDS is caused by the HIV (Human Immunodeficiency Virus) virus, which attacks the immune system, leaving the infected individual vulnerable to opportunistic infection.

Alkaline: basic; having a pH of more than 7.

Allele: One of a set of alternative forms of a gene. Diploid cells possess two homologous chromosomes (one derived from each parent) and therefore two copies of each gene. In a diploid cell, a gene will have two alleles, each occupying the same position on homologous chromosomes.

Alpha Lipoic Acid: Alpha-lipoic acid is an antioxidant and an enhancer of other antioxidants. Normal metabolism and other processes produce oxidative or free radical byproducts that damage all living tissues in the body. The antioxidant properties of alpha-lipoic acid help to protect these tissues from damage caused by aging, sugar metabolism and certain pollutants in our environment and the foods we eat. In, particular, alpha-lipoic acid can reduce damage oxidative damage to blood vessels, brain, peripheral nerves, liver, skin and bone. Other beneficial effects have been demonstrated that are not yet well understood. Alpha-lipoic acid is effectively used to treat neuropathy, muscle fatigue, diabetic insulin resistance, vitamin E deficiency, vascular dysfunction, radiation injury, mushroom poisoning, and alcoholic hepatitis.
It inhibits cataract formation and also frequently used as an anti-aging supplement. Click here for more info.

Alzheimer's disease: a neurological condition characterized by the degeneration of brain cells. Symptoms include memory loss, confusion, and physical decline. Alzheimer's disease usually occurs later in life and worsens over time.

Amino acids: organic (carbon-containing) molecules that serve as the building blocks of proteins.

Anaerobic: refers to the absence of oxygen or the absence of a need for oxygen.

Analog: a chemical compound that is structurally similar to another but differs slightly in composition (e.g., the replacement of one functional group by another).

Anaphylaxis: a rapidly developing and severe systemic allergic reaction. Symptoms may include swelling of the tongue, throat, and trachea, which can result in difficulty breathing, shock, and loss of consciousness. If not treated rapidly, anaphylaxis can be fatal.

Anemia: the condition of having less than the normal number of red blood cells or hemoglobin in the blood, resulting in diminished oxygen transport. Anemia has many cause, including: iron, vitamin B-12, or folate deficiency, bleeding, abnormal hemoglobin formation (e.g., sickle cell anemia), rupture of red blood cells (hemolytic anemia), and bone marrow diseases.

Anencephaly: a birth defect, known as a neural tube defect, resulting from failure of the upper end of the neural tube to close during embryonic development. Anencephaly is a devastating and sometimes fatal birth defect resulting in the absence of most or all of the cerebral hemispheres of the brain.

Angina pectoris: pain generally experienced in the chest, but sometimes radiating to the arms or jaw, due to a lack of oxygen supply to the heart muscle.

Angiography (coronary): a diagnostic test used to identify the exact location and severity of coronary artery disease. During angiography a small tube or catheter is inserted into an artery and guided with the assistance of a fluoroscope (x-ray) to the opening of the coronary arteries which supply blood to the heart. A dye, visible on x-rays, is then injected into each coronary artery to reveal the extent and severity of blockages. Images produced by angiography are known as angiograms.

Anion: a negatively charged ion.

Antagonist: a substance that counteracts the cellular effects of a natural compound, for example, a nutrient or a hormone.

Antibodies: also known as immunoglobulins (Ig), antibodies are specialized proteins produced by white blood cells that circulate in the blood recognizing and binding to foreign proteins, microorganisms or toxins in order to neutralize them. They are a critical part of the immune response.

Anticoagulant: a class of compounds that inhibit the formation of blood clots.

Anticonvulsant: a class of medication used to prevent seizures, commonly used in individuals with seizure disorders or epilepsy.

Antigen: a substance that is capable of causing an immune response.

Antihistamine: a chemical that blocks the affect of histamine in a susceptible tissues. Histamine is released by immune cells during an allergic reaction and also during infection with viruses which cause the common cold. The interaction of histamine with the mucus membranes of the eyes and nose results in "watery eyes" and the "runny nose" often accompanying allergies and colds. Antihistamines can alleviate such symptoms.

Antioxidant: any substance that prevents or reduces damage caused by reactive oxygen species (ROS) or reactive nitrogen species (RNS). ROS and RNS are highly reactive chemicals that attack other molecules and modify their chemical structure. Antioxidants are commonly added to foods to prevent or delay their deterioration due to exposure to air.

Antiresorptive agents: medications or hormones that inhibit bone resorption.

Apoptosis: gene-directed cell death or programmed cell death that occurs when age, condition, or state of cell health dictates. Cells that die by apoptosis do not usually elicit the inflammatory responses that are associated with necrosis. Cancer cells are not able to undergo apoptosis.

Arginine: L-Arginine is crystalline, free-form amino acid. It is a important factor in muscle metabolism and works to transport, store and excrete nitrogen and is involved in DNA synthesis. It is also a precursor of guanidophosphate, phosphoarginine, and creatine, three high-energy compounds found in muscles.

Arrhythmia: an abnormal heart rhythm. The heart rhythm may be too fast (tachycardia), too slow (bradycardia) or irregular. Some arrhythmias, such as ventricular fibrillation, may lead to cardiac arrest if not treated promptly.

Asthma: a respiratory condition characterized by difficulty breathing and reversible narrowing of the airways, known as bronchospasm.

Ataxia: a lack of coordination or unsteadiness usually related to a disturbance in the cerebellum, a part of the brain that regulates coordination and equilibrium.

Atherosclerosis: also known as arteriosclerosis, atherosclerosis results from the accumulation of cholesterol-laden plaque in artery walls. Plaque accumulation causes a narrowing and a loss of elasticity of the arteries, sometimes referred to as hardening of the arteries.

ATP: adenosine triphosphate. An important compound for the storage of energy in cells, as well as the synthesis (formation) of nucleic acids.

Atrophic gastritis: a chronic inflammation of the lining of the stomach, which ultimately results in the loss of glands in the stomach (atrophy) and decreased stomach acid production.

Atrophy: decrease in size or wasting away of a body part or tissue.

Autoimmune disease: Autoimmune diseases occur when the body tissues are mistakenly attacked by its own immune system. The immune system is a complex organization of cells and antibodies designed normally to destroy pathogens, particularly viruses and bacteria that cause infections. Individuals with autoimmune diseases have antibodies in their blood which target their own body tissues.

[Tim Wescott]

"B"

Bacteria: single-celled organisms that can exist independently, symbiotically (in cooperation with another organism) or parasitically (dependent upon another organism, sometimes to the detriment of the other organism). Examples of bacteria include acidophilus (found in yogurt), streptococcus the cause of strep throat, and E. coli (a normal intestinal bacteria, as well as a disease-causing agent).

Bainbridge reflex: The increased heart rate that follows increased pressure or distension of the right atrium.

Balance study: a nutritional balance study involves the measurement of the intake of a specific nutrient as well as the elimination of that nutrient in urine, feces, sweat, etc. If intake is greater than loss of a particular nutrient the individual is said to be in "positive balance." If intake is less than loss, an individual is said to be in "negative balance" for the nutrient of interest.

Ball-and-socket joint: A synovial joint in which the rounded surface of one bone moves within the cup-shaped depression or fossa of another bone, as in the shoulder or hip joint. Also called a spheroid joint.

Basal metabolic rate (BMR): The rate of metabolism measured under standard or basal conditions considered to be awake, at rest and fasting)

Bile: a yellow, green fluid made in the liver and stored in the gallbladder. Bile may then pass through the common bile duct into the small intestine where some of its components aid in the digestion of fat.

Bile acids: components of bile, formed by the metabolism of cholesterol. Bile acid deficiency may lead to the formation of cholesterol gallstones, because bile salts (formed from bile acids) are required to dissolve cholesterol in bile so that it may be eliminated via the intestines.

Bioavailable: the portion of a nutrient (or other chemical) that can be absorbed, transported, and utilized physiologically.

Biomarker: a physical, functional, or biochemical indicator (e.g., the presence of a particular metabolite) of a physiological or disease process.

Blood-brain barrier (BBB): A barrier consisting of specialized brain capillaries and astrocytes that prevents the passage of materials from the blood to the cerebrospinal fluid in the brain.

Bone mineral density (BMD): a term used in quantifying the mineralization of bone. The mineral component of bone consists largely of calcium and phosphorus. BMD is possitively associated with bone strength and resistance to fracture. BMD can be determined through a low radiation X-ray technique known as DEXA.

Bone remodeling: the continuous turnover process of bone that includes bone resorption and bone formation. An imbalance in the regulation of bone remodeling's two contrasting events, bone resorption and bone formation, increases the fragility of bone and may lead to osteoporosis.

Buffer: a chemical used to maintain the pH of a system by absorbing hydrogen ions (which would make it more acidic) or absorbing hydroxyl ions (which would make it more alkaline).

[Tim Wescott]

"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.

[Tim Wescott]

"C" cont.

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.

[Tim Wescott]

"D"

Decarboxylation: A chemical reaction involving the removal of a carboxyl (-COOH) group from a compound.

Decussation: A crossing-over; usually refers to the crossing of 90% of the fibers in the large motor tracts to opposite sides in the medullary pyramids.

Deep fascia: A sheet of connective tissue wrapped around a muscle to hold it in place.

Delta cell: a cell in the pancreatic islets (islets of Langerhans) in the pancreas that secretes somatostatin. Also called a D cell.

Dementia: Significant loss of intellectual abilities such as memory capacity, severe enough to interfere with social or occupational functioning. Criteria for the diagnosis of dementia include impairment of attention, orientation, memory, judgment, language, motor and spatial skills. By definition, dementia is not due to major depression or psychosis. Alzheimer's disease is the most common cause of dementia. Other causes include but are not limited to: AIDS, alcoholism (the dementia is due to thiamine deficiency), insufficient blood flow to the brain (vascular dementia), brain injury, brain tumors, drug toxicity, multiple sclerosis, and infections of the central nervous system.

Dental caries: cavities or holes in the outer two layers of a tooth--the enamel and the dentin. Dental caries are caused by bacteria which metabolize carbohydrates (sugars) to form organic acids which dissolve tooth enamel. If allowed to progress, dental caries may result in tooth decay, infection, and loss of teeth.

Depletion-repletion study: a nutritional study designed to determine the requirement for a specific nutrient. Generally, subjects are placed on a diet designed to deplete them of a specific nutrient over time. Once depletion is achieved, gradually increasing amounts of the nutrient under study are added to the diet until the individual shows evidence of sufficiency or repletion.

Dermatitis: inflammation of the skin. This term is often used to describe a skin rash.

DEXA: dual energy X-ray absorptiometry. A precise instrument that uses the energy from very small doses of X-rays to determine bone mineral density (BMD) and to diagnose and follow the treatment of osteoporosis.

DHA: (Docosahexaenoic Acid – Omega-3 fatty acid) (Pronunciation: doh-KOH-sah-HEX-ah-een-OH-ic). DHA (docosahexaenoic acid is and omega-2 fatty acid that belongs to the class of nutrients called essential fatty acids. DHA, abundant in cold-water fish, is essential for neurological development and for normal brain function in adults. It lowers serum triglyceride levels, making it useful for preventing cardiovascular and other problems. DHA deficiencies are associated with difficulties in learning, attention deficit hyperactivity disorder, unipolar depression, aggressive hostility, senility, sporadic Alzheimer’s, cystic fibrosis and other problems. DHA supplementation improves learning and is useful for hypertension, arthritis, atherosclerosis, depression, adult-onset diabetes, blood clots and some cancers. Read More...

Diabetes (diabetes mellitus): a chronic condition associated with abnormally high levels of glucose (sugar) in the blood. The two types of diabetes are referred to as insulin-dependent (type I) and non-insulin dependent (type II). Type I diabetes results from a lack of adequate insulin secretion by the pancreas. Type II diabetes (also known as adult-onset diabetes) is characterized by an insensitivity of the tissues of the body to insulin secreted by the pancreas (insulin resistance).

Diabetic ketoacidosis: a potentially life-threatening condition characterized by ketosis (elevated levels of ketone bodies in the blood) and acidosis (increased acidity of the blood). Ketoacidosis occurs when diabetes is not adequately controlled.

Diastolic blood pressure: the lowest arterial blood pressure during the heart beat cycle. The diastolic blood pressure is measured while the heart muscle is filling with blood.

Differentiation: changes in a cell resulting in its specialization for specific functions, such as those of a nerve cell. In general, differentiation of cells leads to a decrease in proliferation.

Diffusion: a process, which does not require energy expenditure, by which particles in solution move from a region of higher concentration to one of lower concentration.

Dimer: a complex of two protein molecules. Heterodimers are complexes of two different proteins, while homodimers are complexes of two of the same protein.

Diuretic: an agent that increases the formation of urine by the kidneys, resulting in water loss from the individual using the diuretic.

DNA: deoxyribonucleic acid. A long thread-like molecule made up of large numbers of nucleotides. Nucleotides in DNA are composed of a nitrogen containing base, a 5-carbon sugar (deoxyribose), and phosphate groups. The sequence of bases in DNA serves as the carrier of genetic (hereditary) information.

Docosahexaenoic Acid: See DHA

Double blind: refers to a study in which neither the investigators administering the treatment nor the participants know which participants are receiving the experimental treatment and which are receiving the placebo.

DRI: dietary reference intake. Refers to a set of at least four nutrient-based reference values (RDA, AI, UL, EAR), each with a specific use in defining recommended dietary intake levels for individual nutrients in the U.S. The DRIs are determined by expert panels appointed by the Food and Nutrition Board of the Institute of Medicine.

DV: daily value. Refers to the dietary reference values required as the basis for declaring nutrient content on all products regulated by the U.S. Food and Drug Administration (FDA), including nutritional supplements. The DVs for vitamins and minerals reflect the National Academy of Sciences' 1968 RDAs, and do not reflect the most up to date Dietary Reference Intakes.

[Tim Wescott]

"E"

EAR: estimated average requirement; a nutrient intake value that is estimated to meet the requirement of half of the healthy individuals in a particular life stage and gender group.

Echocardiography: a diagnostic test that uses ultrasound to make images of the heart. It can be used to assess the health of the valves and chambers of the heart, as well as to measure cardiac output.

Ectoderm: The primary germ layer that gives rise to the nervous system and the epidermis of skin and its derivatives.

Effector: An organ of the body, either a muscle or a gland, that responds to a motor neuron impulse.

Eicosanoids: Local hormones derived from a 20-carbon fatty acid (arachidonic acid); two important types are prostaglandins and leukotrienes.

Electroencephalogram (EEG): a recording of the electrical activity of the brain, used to diagnose neurological conditions such as seizure disorders (epilepsy).

Electrolytes: Any compound that separates into ions when dissolved in water and is able to conduct electricity; ionized (dissociated into positive and negative ions) salts in the body fluids. Major electrolytes in the body include sodium, potassium, magnesium, calcium, chloride, bicarbonate, phosphate.

Electron: a stable atomic particle with a negative charge.

Electron transport chain: a group of electron carriers in mitochondria that transport electrons to and from each other in a sequence, in order to generate ATP.

Element: One of the 103 chemical substances that cannot be divided into simpler substances by chemical means. For example, hydrogen, magnesium, lead, and uranium are all chemical elements. Trace elements are chemical elements that are required in very small (trace) amounts in the diet to maintain health. For example, copper, selenium, and iodine are considered trace elements.

Enamel: the hard, white, outermost layer of a tooth.

Endocrine system: the glands and parts of glands that secrete hormones that integrate and control the body's metabolic activity. Endocrine glands include the pituitary, thyroid, parathyroids, adrenals, pancreas, ovaries, and testes.

Enzyme: a biological catalyst. That is, a substance that increases the speed of a chemical reaction without being changed in the overall process. Enzymes are vitally important to the regulation of the chemistry of cells and organisms.

Epidemiologic study: a study examining disease occurrence in a human population.

Epilepsy: also known as seizure disorder. Individuals with epilepsy experience seizures, which are the result of uncontrolled electrical activity in the brain. A seizure may cause a physical convulsion, minor physical signs, thought disturbances, or a combination of symptoms.

Esophagus: a soft muscular tube that connects the throat to the stomach. When a person swallows, the muscular walls of the esophagus contract to push food down into the stomach.

Etiology: the causes or origin of a disease.

Excretion: the elimination of wastes from blood or tissues.

Extracellular fluid (ECF): the volume of body fluid excluding that in cells. ECF includes the fluid in blood vessels (plasma) and fluid between cells (interstitial fluid).

[Tim Wescott]

"F"

Fat: See Triglyceride.

F cell: A cell in the pancreatic islets (islets of Langerharns) that secretes pancreatic polypeptide.

Familial adenomatous polyposis: a hereditary syndrome characterized by the formation of many polyps in the colon and rectum, some of which ultimately develop into colorectal cancer.

Fatty acid: an organic acid molecule consisting of a chain of carbon molecules and a carboxylic acid (COOH) group. Fatty acids are found in fats, oils, and as components of a number of essential lipids, such as phospholipids and triglycerides. Fatty acids can be burned by the body for energy.

Feeding (hunger) center: A cluster of neurons in the lateral nuclei of the hypothalamus that, when stimulated, brings about feeding.

Femoral neck: a portion of the thighbone (femur). The femoral neck is found near the hip, at the base of the head of femur, which makes up the ball of the hip joint. Fractures of the femoral neck sometimes occur in individuals with osteoporosis.

Fibroblast: A large, flat cell that secretes most of the matrix (extracellular) material of the areolar and dense connective tissues.

Fibrocystic breast condition (FCC): a benign (noncancerous) condition of the breasts, characterized by lumpiness and discomfort in one one or both breasts.

Fortification: the addition of nutrients to foods to prevent or correct a nutritional deficiency, to balance the total nutrient profile of food, or to restore nutrients lost in processing.

Fracture: a break in a bone or cartilage, often but not always the result of trauma.

Free radical: a very reactive atom or molecule typically possessing a single unpaired electron.

Fructose: a very sweet 6-carbon sugar abundant in plants. Fructose is increasingly common in sweeteners such as high-fructose corn syrup.

[Tim Wescott]

"G"

Gallbladder: A small pear shaped pouch adjacent to the liver that secretes bile. The gallbladder stores bile which is secreted by the liver and releases bile into the small intestine through the common bile duct.

Gallstones: A solid mass, “pebbles” formed by the precipitation (crystallization) of cholesterol (most common in the U.S. and Europe) or bilirubin (most common in Asia) in the gallbladder. Gallstones may be asymptomatic (without symptoms) or they may result in inflammation and infection of the gallbladder.

Ganglion: Usually, a group of nerve cell bodies lying outside of the central nervous system (CNS); also used for one group of nerve cell bodies within the CNS - the basal ganglia.

Gastroesophageal reflux disease (GERD): a condition in which stomach contents, including acid, back up (reflux) into the esophagus, causing inflammation and damage to the esophagus. GERD can lead to scarring of the esophagus, and may increase the risk of cancer of the esophagus in some patients.

Gastrointestinal: referring to or affecting the stomach and intestines (small and large bowel).

Gene: Biological unit of heredity; a region of DNA that controls a specific hereditary characteristic, usually corresponding to a single protein.

Gene expression: the full use of the information in a gene through transcription and translation leading to production of a protein.

Genome: all of the genetic information (encoded in DNA) possessed by an organism.

Ginko Biloba: (Main function: Improves alertness and circulation). Herb that improves cognition, increases memory and learning in Alzheimer’s patients, alleviates some forms of tinnitus and vertigo, and protects neurons from oxidative damage. Ginko has been known to ameliorate circulation problems, cerebral edema, asthma and sexual dysfunction due to use of antidepressants. People also use Ginko Biloba to treat or prevent atherosclerosis, impotence, depression diabetic retinopathy, macular degeneration and aging – although there is disagreement about its efficacy for these conditions. CAUTION: Ginkgo Biloba is a blood thinner and should not be used along with other blood thinners (i.e. Coumadin, Heparin) unless instructed by a physician. People on MAO inhibitors (i.e. Nardil, Parnate), St. John’s wort, NSAIDs (i.e. Aspirin, Motrin) should be cautious when taking Ginkgo Biloba. Read more...

Gluconeogenesis: the production of glucose from non-carbohydrate precursors, such as amino acids (the building blocks of proteins).

Glucose: a 6-carbon sugar which plays a major role in the generation of energy for living organisms.

Glycogen: a large, highly branched polymer (repeating units) of glucose molecules, used to store energy in muscle and liver cells.

Glycogenesis: The process by which molecules of glucose combine to form a molecule called glycogen.

Glycogenolysis: The breakdown of glycogen into glucose molecules.

Glycolysis: A series of of chemical reactions in the cytosol of a cell in which a molecule of glucose is split into two molecules of pyruvic acid with the production of two molecules of adenosine triphosphate (ATP).

Goiter: enlargement of the thyroid gland. Goiter is one of the earliest and most visible signs of iodine deficiency. The thyroid enlarges in response to persistent stimulation by TSH (see Function). In mild iodine deficiency, this adaptation response may be enough to provide the body with sufficient thyroid hormone. However, more severe cases of iodine deficiency result in hypothyroidism. Thyroid enlargement may also be caused by factors other than iodine deficiency, especially in iodine sufficient countries, such as the U.S.

Goitrogen: a substance that induces goiter formation by interfering with thyroid hormone production or utilization.

Gout: a condition characterized by abnormally high blood levels of uric acid (urate). Urate crystals may form in joints, resulting in inflammation and pain. Urate crystals may also form in the kidney and urinary tract, resulting in kidney stones. The tendency to develop elevated blood uric acid levels and gout is often inherited.

GTP: guanosine triposphate. A high energy molecule, required for a number of biochemical reactions, including nucleic acid and protein synthesis (formation

[Tim Wescott]

"H"

Haldane effect: In the presence of oxygen, less carbon dioxide binds in the blood because when oxygen combines with hemoglobin, the hemoglobin becomes a stronger acid, which combines with less carbon dioxide.

Haploid: Having half the number of chromosomes characteristically found in the somatic cells of an organism; characteristic of mature gametes.

Hartnup's disease: a genetic disorder resulting in defective absorption of the amino acid, tryptophan.

HDL: high density lipoproteins. HDL transport cholesterol from the tissues to the liver where it can be eliminated in bile. HDL-cholesterol is considered good cholesterol, because higher blood levels of HDL-cholesterol are associated with lower risk of heart disease.

Heme: compounds of iron complexed in a characteristic ring structure known as a porphyrin ring.

Hemodialysis: a medical procedure that uses a specialized machine to filter waste products from the blood, while restoring its normal constituents. Hemodialysis is needed to perform the work of the kidneys if they can no longer function effectively.

Hemoglobin: the oxygen-carrying pigment in red blood cells.

Hemolysis: rupture of red blood cells.

Hemolytic anemia: Anemia resulting from hemolysis (the rupture of red blood cells).

Hemorrhage: excessive or uncontrolled bleeding.

Hepatic: Refers to the liver.

Hepatitis: literally, inflammation of the liver. Hepatitis caused by a virus is known as viral hepatitis. Other causes of hepatitis include toxic chemicals and alcohol abuse.

Hereditary spherocytosis: a hereditary form of anemia characterized by abnormally shaped red blood cells which are spherical and abnormally fragile. The increased fragility of these red blood cells leads to hemolytic anemia (anemia caused by the rupture of red blood cells).

Heterodimer: a dimer or complex of two different molecules, usually proteins.

Heterozygous: possessing two different forms (alleles) of a specific gene.

HIV: human immunodeficiency virus. The virus that causes AIDS.

Homocysteine: a sulfur-containing amino acid, which is an intermediate in the metabolism of another sulfur-containing amino acid, methionine. Elevated homocysteine levels in the blood have been associated with increased risk of cardiovascular disease.

Homodimer: a dimer or complex of two of the same molecule, usually a protein.

Homologous: having the same relative position, value, or structure.

Homozygous: possessing two identical forms (alleles) of a specific gene.

Hormone: a chemical secretion released by a gland or a tissue, which affects or regulates the activity of specific cells or organs. Complex bodily functions, such as growth and sexual development, are regulated by hormones.

Human growth hormone (HGH): Hormones secreted by the anterior pituitary gland that stimulates growth of body tissues, especially skeletal and muscular tissues. Also known as somatotropin and somatotropic hormone (STH).

Huperzine-A: (Main function: acetylcholine esterase inhibitor) (Pronunciation: hoo-PEHR-zeen). Huperzine is an alkaloid found in the club moss, Huperzia serrata – a plant used in Chinese traditional medicine. Huperzine is a potent inhibitor of the enzyme that disposes of acetylcholine in the brain; it therefore elevates acetylcholine levels. When taken orally, huperzine has shown a high bioavailability and rapid penetration into the brain. Side effects are minimal at therapeutic doses. Huperzine exhibits memory-enhancing activities in animals and humans. Its benefits are said to include increased alertness, greater short-term memory retention and increased energy. Huperzine shows promise for treating Alzheimer’s disease and other dementias because: It reduces oxidative damage produced by beta-ameloid protein (a protein overproduced in Alzheimer’s brains); It elevates acetylcholine levels that are typically depleted by Alzheimer’s; It has demonstrated ability to enhance memory; It has a longer duration of action and higher therapeutic index than tacrine and donepezil (the best FDA-approved Alzheimer’s drugs). Read more...

Hydroxyapatite: a calcium phosphate salt. Hydroxyapatite is the main mineral component of bone of bone and teeth, and is what gives them their rigidity.

Hydroxylation: a chemical reaction involving the addition of a hydroxyl (-OH) group to a compound.

Hyperparathyroidism: excess secretion of parathyroid hormone by the parathyroid glands resulting in the disturbance of calcium metabolism. Symptoms may include increased blood levels of calcium (hypercalcemia), decreased blood levels of phosphorus, loss of calcium from bone, and kidney stone formation.

Hypertension: high blood pressure, defined as a systolic blood pressure greater than 140 mm Hg and/or diastolic blood pressure greater than 90 mm Hg.

Hyperthyroidism: an excess of thyroid hormone which may result from an overactive thyroid gland or nodule, or from taking too much thyroid hormone.

Hypoparathyroidism: a deficiency of parathyroid hormone, which may be characterized by low blood calcium levels (hypocalcemia).

Hypothalamus: An area at the base of the brain that regulatesbodily functions, such as body temperature, hunger, and thirst.

Hypothesis: an educated guess or proposition that is advanced as a basis for further investigation. A hypothesis must be subjected to an experimental test to determine its validity.

Hypothyroidism: a deficiency of thyroid hormone which is normally made by the thyroid gland, located in the front of the neck.