Taking a lot of vitamin A every day for about three weeks might make your body break down beta-carotene (from food) into vitamin A less efficiently.

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Against

Evidence from Studies

Supporting (1)

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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

Cross-Sectional Study

Human

2003 Aug

Contradicting (0)

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No contradicting evidence found

Gold Standard Evidence Needed

According to GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this specific claim, ordered from strongest to weakest evidence.

Source 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

Score: 24

DOI: 10.1194/JLR.M300116-JLR200

Similar Assertions

Taking a lot of vitamin A every day for about three weeks might help two healthy people absorb more beta-carotene from their food, based on how much showed up in their urine over the next month.

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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.

83%

After taking vitamin A supplements for three weeks, two people ended up getting more usable vitamin A from beta-carotene—even though their bodies were breaking it down less, which is kind of surprising.

74%