Vitamin D Council Glossary

Rachitic

Affected with, suffering from, or characteristic of rickets.

Radiology (Radiologically)

The use of X-rays and radioactive substances in the diagnosis and treatment of disease.

Radiopacity

A measurement of the ability of electromagnetic radiation, such as an X-ray, to pass through a particular material.

Randomized controlled trial

Study design used for determining whether a cause-effect relation exists between treatment and outcome. Also useful for assessing the cost-effectiveness of a treatment.

Rate-limiting step

The slowest step in a reaction that determines the overall rate.

Reactive oxygen species

Natural byproducts of oxygen metabolism that are highly reactive and significantly damage cell structures.

Recommended Daily Allowance (RDA)

The average daily dietary intake level that is sufficient to meet the nutrient requirement of nearly all healthy individuals in a particular life stage and gender group.

Retinoic acid

Oxidized form of vitamin A that is a regulator substance in morphogenesis. Also functions in the growth and development of bone and the maintenance of epithelium.

Retinoid (Retinoids)

One of various natural or synthetic derivatives of vitamin A that has many important and diverse functions throughout the body including roles in vision, regulation of cell proliferation and differentiation, growth of bone tissue, immune function, and activation of tumor suppressor genes.

Retinol

Animal form of vitamin A that belongs to the family of chemical compounds known as retinoids.

Retinopathy

Non-inflammatory damage to the retina of the eye that is usually a result of blood supply problems.

Ribonucleic acid (RNA)

Nucleic acid polymer important in the translation of genetic information from DNA into protein products.