In vitro

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

In vivo

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

Insulin resistance

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).

International Unit (IU)

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.

Intervention trial / Experimental study

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.


Two or more substances that are composed of the same elements in the same proportions but differ in properties because of differences in the arrangement of atoms. Cis- and trans-isomerism, for example, refers to the arrangement of atom groups adjacent to a carbon-carbon double bond (C=C); in the ‘cis-isomer’ the groups are on the same side of the double bond, while in the ‘trans-isomer’ they are on opposite sides.