Carotenoids

Carotenoids are a large family of naturally occurring pigments characterized by an extended system of conjugated double bonds. They are produced by plants, algae, and many microorganisms and contribute yellow, orange, and red coloration to many biological tissues and foods. Humans cannot synthesize carotenoids and therefore obtain them primarily from the diet .^1,2

Carotenoids generally have an isoprenoid structure built around a long conjugated chain. This structure is responsible for their characteristic light absorption and color. Carotenoids are commonly divided into two chemical groups: carotenes, which contain only carbon and hydrogen, and xanthophylls, which also contain oxygen. Beta-carotene and lycopene are carotenes, whereas lutein and zeaxanthin are xanthophylls .¹

Some carotenoids function as provitamin A compounds, meaning that the human body can enzymatically convert them into vitamin A. Beta-carotene, alpha-carotene, and beta-cryptoxanthin have provitamin A activity. Other dietary carotenoids, including lycopene, lutein, and zeaxanthin, cannot be converted into vitamin A and are classified as non-provitamin A carotenoids .²

Carotenoid is therefore a broader term than beta-carotene or provitamin A. Beta-carotene is one specific carotenoid, and vitamin A formation is only one possible metabolic fate of certain members of this chemically diverse family. Different carotenoids have distinct structures, absorption patterns, tissue distributions, and metabolic pathways .^1,2