The Claim

In two healthy adult individuals, daily supplementation with 10,000 IU of vitamin A for approximately 21 days was associated with a roughly 10-fold reduction in the urinary excretion of labeled compounds after ingestion of [14C]beta-carotene.

Source: Absorption and retinol equivalence of β-carotene in humans is influenced by dietary vitamin A intake Published, JLR Papers in Press, June 1, 2003. DOI 10.1194/jlr.M300116-JLR200

What the research says

Supports is higher

Support is ahead, but a single strong opposing study can change this.

Supports
24score
Challenges
0score

These are independent scores, not a percentage. Higher-grade studies count more, so a single strong opposing study can outweigh several weaker ones.

Correlation
1 study reviewed
In plain English

Taking a specific dose of vitamin A every day for about three weeks might make your body get rid of much less of a certain form of beta-carotene through urine, based on a small observation in two healthy adults.

See the scientific wording

In two healthy adults, vitamin A supplementation at 10,000 IU/day for about 21 days was associated with an approximately 10-fold reduction in urinary excretion of labeled compounds following ingestion of [14C]beta-carotene.

What the research says

1 study
  1. Study: Absorption and retinol equivalence of β-carotene in humans is influenced by dietary vitamin A intake Published, JLR Papers in Press, June 1, 2003. DOI 10.1194/jlr.M300116-JLR200

    The study gave two people a vitamin A supplement for about 3 weeks and found it caused a big drop in the amount of a special marker in their urine after they ate a form of vitamin A from plants. This matches exactly what the claim says.

Score breakdown, mechanism chain, raw evidence, ideal studies needed & 1 supporting studies

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