GLOSSARY

Beta-Carotene is a provitamin A carotenoid in carrots and other vegetables, differing from retinol in conversion and risk.

Carotenoid is a pigment-family name, not a guarantee of provitamin A activity: lutein and lycopene should not be counted as retinol. Beta-carotene, alpha-carotene and beta-cryptoxanthin can contribute, with differing activity per mass. Varied fruit and vegetable colours diversify compounds, not identical vitamin doses from every colour or member.

Retinol activity equivalents compare vitamin A activity rather than simply adding pigment masses. Under the common convention, 1 microgram retinol corresponds to 12 micrograms dietary beta-carotene or 24 micrograms dietary alpha-carotene or beta-cryptoxanthin. These factors depend on form and source; supplemental beta-carotene uses a different factor, so the label's basis must be identified.

A precursor can be converted into a vitamin form or related product, but conversion need not be complete or identical between people. Precursor mass cannot automatically be equated with active-vitamin mass. Digestive function, food properties and metabolic regulation matter; precursor also does not mean inactive in every respect or beneficial without quantity limits.

Ordinary carrots are not equivalent to high-dose beta-carotene supplements, particularly when assessing a smoker's exposure.

Liver and some animal or fortified foods provide preformed vitamin A; dark-green and orange vegetables can provide precursors. Contributions vary with food and portion. For athletes, varied sources are more useful than frequent liver consumption or stacking retinol products. Accompanying energy and fat also belong in the actual meal plan rather than being ignored because a vitamin is present.

Chronically excessive preformed vitamin A can cause toxicity, with pregnancy requiring particular care. Food carotenoids are not simply equivalent in risk, but high-dose beta-carotene supplements are also not safe for everyone, especially smokers. Source, form and amount matter; a capsule being plant-derived does not guarantee that it is appropriate or harmless.

Bioavailability concerns the fraction absorbed and available for use, with package content only the starting point. Food matrix, cooking, chemical form and individual conditions can alter it. Natural or active branding alone does not establish universal superiority. Compare actual amounts, appropriate units and evidence for the particular preparation rather than relying on a promotional word.