“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 […]

“Cross-over trial” — a clinical trial in which at least two interventions or treatments are applied to the same individuals after an appropriate wash-out period. One of the treatments is often a placebo. In a randomized cross-over design, interventions are applied in a randomized order to ensure that the order of treatments did not contribute […]

“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.

“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.

“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.