Compound or practice · Supplement

Beta-Carotene

A provitamin-A carotenoid that's healthy from food but became the cautionary tale of supplements — high doses raised lung-cancer risk in smokers.

Overall grade: Grade C
Last revised: Jul 10, 2026; 2
graded outcomes: 0
references listed

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A structured monograph in Prometheus's bundled library. Its grades are the monograph's own reading of the evidence, not a peer-reviewed review.

2 at grade B — 2 graded rows

What is known

Each outcome with its grade (how strong the evidence is, A to D), the size of the effect where the entry records one, and how often studies agree.

Outcome	Grade	Effect size	Agreement
Vitamin-A statusCorrects deficiency	Evidence grade B	Moderate	high
Lung cancer (smokers, high-dose)Increased risk	Evidence grade B	Small	high

Vitamin-A statusEvidence grade B
Corrects deficiency
Moderatehigh
Lung cancer (smokers, high-dose)Evidence grade B
Increased risk
Smallhigh

The evidence in words

What it is

Beta-carotene is an orange plant pigment the body converts to vitamin A, found in carrots and leafy greens.

How it works

It's converted to retinol as needed (a safe way to get vitamin A) and acts as an antioxidant pigment.

What the evidence shows

Carotenoid-rich diets track with better health, but isolated high-dose beta-carotene supplements famously increased lung-cancer risk in smokers (ATBC, CARET trials) — a landmark reminder that an isolated supplement can behave unlike the food. Modest doses help correct vitamin-A deficiency.

Safety & interactions

Food amounts are safe (excess just yellows skin). High-dose supplements are contraindicated in smokers and asbestos-exposed people.

Bottom line

Get carotenoids from food. Skip isolated high-dose beta-carotene supplements — especially if you smoke.

Entries that share this one's tags or conditions.

Beta-Carotene for Lung cancer (smokers, high-dose)Evidence grade B — Increased riskEvidence grade B
Beta-Carotene for Vitamin-A statusEvidence grade B — Corrects deficiencyEvidence grade B
Beta-Carotene: side effects, safety & interactionsFood amounts are safe (excess just yellows skin). High-dose supplements are contraindicated in smokers and asbestos-expoEvidence grade C
ChagaAn antioxidant-rich fungus with essentially no human trials — and a real oxalate/kidney caution.Evidence grade D

Sources

This entry lists no references of its own.

Last revised Jul 10, 2026. A grade is this entry's reading of the evidence, not medical advice.