A group of electron carriers in mitochondria that transport electrons to and from each other in a sequence, in order to generate compounds for the storage of energy in cells such as adenosine triphosphate (ATP). ATP serves as the cell's major energy source and drives a number of biological processes including muscle contraction and the production of protein.

An organic molecule that catalyzes (i.e., increases or decreases the rates of) chemical reactions. Enzymes are vitally important to the regulation of the chemistry of cells and organisms. Nearly all known enzymes are proteins.

A study that investigates factors affecting the health and illness of populations, and serves as the foundation for interventions (treatment) made in the interest of public health and preventive medicine. 
 
An epidemiological or population study is considered a cornerstone methodology of public health research for identifying risk factors for disease and determining optimal treatment. However, as such a study is usually based on observational or survey design it can only generate a hypothesis. For testing a hypothesis a randomized controlled trial is essential.

The average daily dietary intake level of a nutrient expected to satisfy the needs of 50% of the people in that age group.

A fatty acid consists of the elements carbon (C), hydrogen (H) and oxygen (O) arranged as a carbon chain skeleton with a carboxyl group (-COOH) at one end. Fatty acids can be “saturated” and “unsaturated”. Saturated fatty acids have all the hydrogen that the carbon atoms can hold; they are saturated with hydrogen atoms. Unsaturated fatty acids are not saturated with hydrogen, and therefore, have double bonds (=) between the carbons atoms. While “monounsaturated fatty acids” have only one double bond, “polyunsaturated fatty acids” have more than one double bond. Fatty acids are frequently represented by a notation such as “C18:2”, which indicates that the fatty acid consists of an 18-carbon chain and 2 double bonds.

Free radicals are unstable molecules (e.g., oxygen) with an unpaired electron. They are very reactive, (e.g., reactive oxygen species) trying to capture the needed electron to gain stability. Generally, free radicals attack the nearest stable molecule, "stealing" its electron. When the attacked molecule loses its electron, it becomes a free radical itself, beginning a chain reaction. Once the process is started it can cascade, finally resulting in the disruption of a living cell. Some free radicals arise normally during metabolism. Sometimes the body’s immune system’s cells create them to neutralize viruses and bacteria. However, environmental factors such as pollution, radiation, cigarette smoke and herbicides can also generate free radicals.

Referring to or affecting the digestive tract, which includes the mouth, throat (pharynx), gullet (esophagus), stomach and bowel (intestines).

Process by which information from a gene is used in the synthesis of a functional gene product – often a protein. Gene expression starts with transcription; the production of RNA copies of the DNA section coding for the gene to be expressed. This RNA transcript may then be translated into a protein.

A condition in which women without previously diagnosed diabetes exhibit high blood glucose levels during pregnancy.

Proteins that bind to DNA and package it into compact structures to form nucleosomes—integral structural components of chromosomes. The compact packaging of DNA must be relaxed somewhat for DNA copying (replication) and gene expression (‘transcription’) to occur. Modification of histones through the attachment of acetyl (-COCH3) or methyl (-CH3) groups (acetylation or methylation), and of biotin (biotinylation) has been shown to affect the structure of histones, thereby affecting replication and transcription of DNA.

A sulfur-containing amino acid, which is an intermediate in the metabolism of methionine, another sulfur-containing amino acid.  Homocysteine appears to be a nerve and vessel toxin, promoting mortality and cardiovascular disease as well as stroke, Alzheimer's disease, birth defects, recurrent pregnancy loss, and eye disorders.

Elevated homocysteine levels in the blood have been associated with increased risk of cardiovascular disease. Most research indicates that a blood plasma homocysteine level of less than 10 micromoles/liter is associated with a lower risk of cardiovascular disease and a reasonable treatment goal for individuals at high risk. However, it is not yet clear whether lowering homocysteine levels will reduce cardiovascular disease risk.

The metabolism of homocysteine provides an example of the interrelationships among nutrients necessary for optimum physiological function and health: the amount of homocysteine in the blood is regulated by three vitamins: vitamin B9, vitamin B12, and vitamin B6.

A molecule released by cells into the blood to act as chemical “messenger”, transporting a signal from one cell to another. Cells respond to a hormone when they produce a specific receptor for that hormone. The hormone binds to the receptor protein, resulting in the activation of a signal transduction mechanism that ultimately leads to cell type-specific responses.

An inherited degenerative disorder of the brain. Symptoms include movement disorders and impaired cognitive function. Symptoms typically develop in the fourth decade of life and progressively deteriorate over time.

A medical condition in which the blood pressure is permanently (chronically) elevated. Persistent hypertension is one of the risk factors for strokes, heart attacks and heart failure, and is a leading cause of chronic kidney (renal) failure. Beginning at a systolic pressure of 115 mmHg and a diastolic pressure of 75 mmHg (commonly written as 115/75 mmHg), cardiovascular disease risk doubles for each increment of 20/10 mmHg. A normal blood pressure is 90–119/60–79 mmHg.

A test or research done in the test tube (“in glass”), outside a living organism.

An assay that evaluates a biological process occurring inside the body (“inside a living organism").

A condition in which normal amounts of insulin (hormone responsible for glucose uptake from blood) are inadequate to produce a normal insulin response, resulting in elevated levels of fat in the blood (associated with diabetes mellitus Type 2), reduced glucose uptake in muscle, and impaired glucose storage in liver (contributing to elevated blood glucose levels).

A unit of measurement for the amount of a substance (e.g., vitamin), based on measured biological activity or effect.

Vitamin A
1 IU is the biological equivalent of 0.3 micrograms (mcg) retinol, or of 0.6 micrograms beta-carotene; 1 nanogram (ng)/ml = 3.5 nanomol (nmol)/l.
 
Vitamin C
1 IU is 50 micrograms (mcg) L-ascorbic acid; 1 ng/ml = 5.5 nmol/l.
 
Vitamin D
1 IU is the biological equivalent of 0.025 micrograms (mcg) cholecalciferol/ergocalciferol; 1 ng/ml = 2.5 nmol/l.

Vitamin E
1 IU is the biological equivalent of about 0.667 mg d-alpha-tocopherol, or of 1 mg of dl-alpha-tocopherol acetate; 1 ng/ml = 2.78 nmol/l.

A study (usually a clinical trial) in which the investigators actively intervene/experiment to test a hypothesis (e.g., the effect of a treatment or intervention on a health- or disease-related outcome).

Conclusions of intervention studies (e.g., randomized controlled trials) can be inaccurate when they try to transfer effects of an intervention (e.g., a high-dose micronutrient therapy) seen in patients or vulnerable groups (e.g., smokers) to consumers using a particular factor in the interest of prophylaxis (e.g., taking fortified foods and/or dietary supplements to prevent micronutrient deficiency).

An atom or molecule with an (positive or negative) electrical charge.