Ecological study

An epidemiological study that examines the relationships between exposures and disease rates in a series of populations (e.g., different countries). Ecological studies often rely on published statistics such as food disappearance data or disease-specific death rates.


A substance (ionic salt) that dissociates into charged particles (ions) in solution, making it capable of conducting electricity.

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 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.

Epidemiological study / Population study

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 healthresearch 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.

Estimated Average Requirements (EAR)

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