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Labeled 5-methyltetrahydrofolate appeared in plasma; appearance was about 0.6 ± 0.2 nmol/h versus 7 ± 1.2 nmol/h after a separate 172-nmol intravenous administration. This demonstrates colonic absorption of a supplied folate preparation under the study conditions. It does not quantify habitual microbial folate contribution, prove a shikimate intervention, or establish equal absorption of every microbial folate form. [Folate is absorbed across the colon of adults: evidence from cecal infusion of (13)C-labeled [6S]-5-formyltetrahydrofolic acid.](https://pubmed.ncbi.nlm.nih.gov/19439459/)","model_system":"Cecal 684-nmol isotope administration; separate intravenous comparator.","directness":"reported_statement","verification_status":"source_recorded","notes":"Exact excerpt of the retained AI-assisted reviewed reference; primary sources are cited in primary_references and access scope is retained. 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