Vitamin A

Vitamin A is defined by form.

It exists in two primary categories:

• Preformed vitamin A (retinoids) — such as retinol and retinyl esters, directly active
• Provitamin A carotenoids — such as beta-carotene, which require conversion

These forms are not equivalent.

At a high level, evaluation comes down to three signals:

• Form type — whether the product delivers active retinoids or conversion-dependent carotenoids
• Dose and accumulation — relevance of intake in the context of fat-soluble storage
• Conversion efficiency — variability in how carotenoids are transformed into active vitamin A

Vitamin A is fat-soluble.

It is stored in the body rather than rapidly excreted.

This changes how dose should be interpreted.

Retinoids provide direct activity.
Carotenoids provide potential.

The two are often grouped under a single label.
Their behavior is not interchangeable.

Form determines both function and risk.
Context defines appropriate intake.