Vitamin b12 absorption timing
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Timing of Vitamin B12 Absorption in Humans
Circadian Variation in Vitamin B12 Absorption
Research shows that the time of day significantly affects how well vitamin B12 is absorbed. In a study with healthy volunteers, absorption was highest when vitamin B12 was taken at 1:00 PM compared to early morning (7:00 AM), evening (7:00 PM), or night (1:00 AM). This suggests that midday may be the optimal time for vitamin B12 absorption, likely due to circadian rhythms influencing gastrointestinal function .
Absorption Kinetics and Peak Timing
After taking an oral dose of vitamin B12, blood levels of the vitamin typically peak between 8 to 12 hours post-ingestion. This delayed peak indicates that vitamin B12 is absorbed slowly through the digestive tract, with the highest concentrations in the blood occurring several hours after intake . Another study measuring absorption after a single dose of multivitamin found significant increases in serum vitamin B12 and its active form (holo-transcobalamin) between 6 and 10 hours after dosing, further supporting the idea of a delayed absorption window .
Late and Colonic Absorption
In addition to the main absorption in the small intestine, a smaller, late absorption peak was observed about 8.7 hours after dosing, accounting for roughly 12% of total absorption. This late phase may be due to some vitamin B12 being absorbed in the colon, although this accounts for a much smaller portion compared to the small intestine .
Dose-Dependent Absorption and Saturation
Vitamin B12 absorption is also influenced by the amount taken at one time. Active absorption saturates at doses around 1.2–2.5 micrograms, with higher doses resulting in a lower percentage absorbed, likely due to the body’s limited capacity for active transport. At higher doses, a small amount is absorbed passively, but this is much less efficient .
Conclusion
Vitamin B12 absorption is highest when taken around midday, with blood levels peaking 8–12 hours after ingestion. While most absorption occurs in the small intestine, a small amount can be absorbed later in the colon. The body’s ability to absorb vitamin B12 is also limited by dose, with active absorption saturating at relatively low amounts. For optimal absorption, timing and dose should be considered, with midday intake potentially offering the best results 12356.
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