Your body can only absorb a little bit of vitamin B12 at a time—about as much as what’s in a single serving of meat or fish. If you eat or take way more than that in one meal, your body just can’t use the extra, so most of it goes to waste.

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Evidence from Studies

Supporting (1)

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Vitamin B12 Sources and Bioavailability

Narrative Review

2007 Nov

The study says your body can only absorb a little bit of vitamin B12 at a time—about 1.5 to 2 micrograms per meal—and if you eat more than that, your body can’t use the extra. This matches exactly what the claim says.

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

Vitamin B12 Sources and Bioavailability

Score: 1

DOI: 10.3181/0703-MR-67

Similar Assertions

When you eat fish, sheep meat, or chicken, your body absorbs vitamin B12 from them at different rates—fish gives you about 42% of the B12, sheep meat gives you 56% to 89%, and chicken gives you 61% to 66%, so not all meats give you the same amount of this important vitamin.

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76%

If you eat twice as much vitamin B12 from food, your blood levels of B12 don’t go up much—your body just doesn’t absorb it very well, especially as you get older.

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72%