Cardiovascular disease

Diseases affecting the heart and blood vessels, encompassing a number of conditions that result from atherosclerosis, including heart attack (myocardial infarction), congestive heart failure, and stroke.

Cardiovascular system

The blood, heart, and blood vessels form the cardiovascular system.

Carpal tunnel syndrome

A disorder that causes numbness, pain, and weakness of the hand and fingers due to compression of the median nerve at the wrist. It may result from repetitive stress injury of the wrist or from soft tissue swelling, which sometimes occurs with pregnancy or thyroid hormone deficiency (hypothyroidism).

Case reports

(also known as anecdote, case history, or single case report)
Individual observations based on small numbers of subjects.

Case reports are considered to provide weak empirical evidence because the risk of bias is very high. Case reports may indicate areas for further research.

Case-control study

A study that compares retrospectively people with a specific disease or outcome of interest (cases) to people from the same population without that disease or outcome (controls), and which seeks to find associations between the outcome and prior exposure to a particular factor of interest (e.g., a micronutrient).

Due to the potential for many forms of bias (e.g., when selecting cases and controls or recalling nutrition behaviors) in this study type, case control studies provide relatively weak empirical evidence even when properly executed.


A process in which the rate (speed) of a chemical reaction is either increased (accelerated) or decreased (slowed down, inhibited) by a chemical substance known as catalyst. The catalyst, unlike other reagents that participate in the chemical reaction, is not consumed by the reaction itself and may participate in multiple chemical transformations.


A clouding of the lens of the eye, progressively impairing vision. Cataracts appear to be formed by protein oxidation in the lens of the eye; such oxidation may be prevented by antioxidants, such as vitamin A, vitamin C, vitamin E, and beta-carotene.

Cerebrovascular diseases

A group of brain dysfunctions related to disease of blood vessels supplying the brain. Hypertension is the most important cause of damage to the blood vessels, which can result in stroke.


A compound that is an integral structural component of cell membranes and a precursor in the synthesis of steroid hormones. Dietary cholesterol is obtained from animal sources but is also synthesized by the liver. Cholesterol is carried in the blood by lipoproteins: low-density lipoproteins (LDL) and high-density lipoproteins (HDL).

Chronic disease

A disease that is long-lasting or recurrent.

Clinical trial

(also known as an intervention study)
An intervention trial generally used to evaluate the efficacy and/or safety of a treatment or intervention in human participants.


A molecule that binds to an enzyme and is required for its biological activity. Many coenzymes are derived from vitamins.


A compound that is essential for the activity of an enzyme.

Cognitive performance

Quality of mental information processing, including perception, attention, reaction time (sensorimotor speed), decision making, problem solving, and memory.

Cohort study

An observational study in which a defined group of people (the cohort) is followed over time. The outcomes of people in subsets of this cohort are compared to examine people who were exposed or not exposed (or exposed at different levels) to a particular intervention or other factor of interest (e.g., a vitamin). Cohort studies are either prospective or retrospective

Because of their
 observational nature, cohort studies do not provide empirical evidence that is as strong as that provided by properly executed randomized controlled clinical trials.


A fibrous protein that is the basis for the structure of skin, tendon, bone, cartilage and all other connective tissue.


Referring to the portion of the large intestine that includes the colon (extending from the end of the small intestine) and the rectum (the last portion of the large intestine, connecting the colon to the anus).

Congestive heart failure (CHF)

A condition in which the heart loses the ability to pump blood efficiently enough to meet the demands of the body. Symptoms may include swelling (edema), shortness of breath, weakness and exercise intolerance.

Controlled trial

A clinical trial that has a control (placebo) group. Such trials are not necessarily randomized.

Coronary Heart Disease (CHD)

Result of atherosclerosis of the heart (coronary) arteries: narrowing or blockage of the coronary arteries, which is the underlying cause of heart attack (myocardial infarction).