Vitamin b absorption timing
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Vitamin B12 Absorption Timing: Key Markers and Timeframes
Early and Delayed Absorption Peaks of Vitamin B12
Research shows that after oral intake of vitamin B12, absorption and appearance in the blood are not immediate. In healthy adults, a significant increase in vitamin B12 markers, such as holo-transcobalamin (holo-TC), is first seen at around 6 hours after ingestion, with the largest increase observed at 24 hours post-dose 146. Another study found that after a single oral dose, there is a late absorption peak, accounting for about 12% of total absorption, which occurs after an average lag time of 8.7 hours from dosing . This suggests that vitamin B12 absorption is a gradual process, with both early and delayed peaks.
Measurement of Absorption Using Blood Markers
Holo-TC and transcobalamin saturation are considered the best markers for recent vitamin B12 absorption, showing larger and more consistent increases than total serum vitamin B12 after oral intake 1456. Increases in these markers are typically measured at 6 to 24 hours after dosing, with a 15% or greater rise indicating effective absorption 156. Measuring these markers at 24 hours post-dose is recommended for assessing absorption efficiency 14.
Absorption from Different Intestinal Sites
Most vitamin B12 is absorbed in the small intestine, but studies also show that a small amount (about 7%) can be absorbed from the colon, with this process occurring over several hours 23. The appearance of vitamin B12 in the plasma is delayed, with peak concentrations not appearing until 8 to 12 hours after administration, supporting the idea that absorption is slow and may occur lower in the intestine .
Practical Implications for Supplement Timing
Both multivitamin gummies and tablets containing vitamin B12 show similar absorption patterns, with significant increases in blood markers observed between 6 and 10 hours after a single dose . This means that blood tests to assess vitamin B12 absorption should ideally be performed 6 to 24 hours after oral intake for the most accurate results 1456.
Conclusion
Vitamin B12 absorption after oral intake is a gradual process, with significant increases in blood markers like holo-TC and transcobalamin saturation typically observed between 6 and 24 hours post-dose. Measuring these markers at 24 hours provides the best indication of absorption efficiency. Both the small intestine and, to a lesser extent, the colon contribute to vitamin B12 absorption, and the timing of blood sampling is crucial for accurate assessment.
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