A landmark study examining vitamin B12 absorption reveals a counterintuitive finding: even at extremely low absorption percentages, high-dose supplements deliver substantial amounts of the essential nutrient. When patients consume a 1,000 microgram dose, only 1.3% is absorbed—yet this still yields approximately 13 micrograms of bioavailable B12, exceeding five times the daily recommended intake. This efficiency paradox occurs because the body’s primary absorption mechanism, intrinsic factor, saturates at just 1.5 micrograms per dose. Beyond this threshold, a secondary passive diffusion pathway activates, absorbing 1-2% of any additional B12 consumed. For patients with compromised intrinsic factor function or those requiring rapid repletion, this backup system becomes clinically significant. The research clarifies why high-dose supplementation remains an effective therapeutic strategy despite appearing inefficient on paper. Read the full article on GMJ Newsroom.
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