{"id":"399c1c74-8848-50b3-aa66-567b38797576","stable_key":"dff9f743-3766-5f20-a71e-d6d2bd5bfb6f:va-iron-absorption-no-enhancement2003","predicate":"did_not_enhance","statement":"Five isotope studies did not confirm enhanced iron absorption after adding retinyl palmitate to corn-bread meals.","claim_class":"observational","status":"source_derived_draft","evidence_grade":"ungraded","direction":"neutral","is_public":true,"mechanism_event_id":"af3eb481-f524-54ac-8d45-02fa1c6301ce","mechanism_event_label":"Follow-up experiments did not reproduce the earlier positive result.","subject":{"id":"62e3f5bd-503b-5ea8-b102-966aa3b7319c","slug":"retinyl-palmitate","display_name":"All-trans-retinyl palmitate","entity_type_key":"small_molecule"},"object":{"id":"4429d8ae-d732-5f5e-acc1-2c872e23da62","slug":"nonheme-iron-absorption","display_name":"Nonheme iron absorption","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"af3eb481-f524-54ac-8d45-02fa1c6301ce","stable_key":"dff9f743-3766-5f20-a71e-d6d2bd5bfb6f:va-iron-absorption-no-enhancement2003-event","event_type":"observed_intervention","label":"Follow-up experiments did not reproduce the earlier positive result.","description":"Five isotope studies did not confirm enhanced iron absorption after adding retinyl palmitate to corn-bread meals.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"89bcaf42-b4ab-5760-8c2e-44eace10cee0","slug":"iron","display_name":"Iron","entity_type_key":"nutrient_element"},"role":"absorbed_nutrient","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"62e3f5bd-503b-5ea8-b102-966aa3b7319c","slug":"retinyl-palmitate","display_name":"All-trans-retinyl palmitate","entity_type_key":"small_molecule"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"4429d8ae-d732-5f5e-acc1-2c872e23da62","slug":"nonheme-iron-absorption","display_name":"Nonheme iron absorption","entity_type_key":"cellular_process"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"Vitamin A/iron absorption replication disagreement.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Water/coffee meal conditions; stable and radioisotope methods.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Possible effect modification by poor vitamin A status remained unresolved; beta-carotene was not directly retested.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"Vitamin A research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"vitamin-a","display_name":"Vitamin A","entity_type_key":"chemical_species"}},{"dimension":"organism","value_text":"Homo sapiens","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Follow-up experiments did not reproduce the earlier positive result.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[va-walczyk2003] No enhancing effect of vitamin A on iron absorption in humans (2003). https://pubmed.ncbi.nlm.nih.gov/12499334/ DOI: 10.1093/ajcn/77.1.144","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"Intestinal absorption","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"c42254c4-2175-5f7f-aa01-13e29b8e266b","evidence_kind":"source_excerpt","locator":"Lines 1566-1576","start_line":1566,"end_line":1576,"excerpt":"### va-iron-absorption-no-enhancement2003\nFive isotope studies did not confirm enhanced iron absorption after adding retinyl palmitate to corn-bread meals.\nCondition category: normal\nnutrient_topic: Vitamin A research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: Follow-up experiments did not reproduce the earlier positive result.\norganism: Homo sapiens\ntissue_or_cell_type: Intestinal absorption\nexperimental_model: Water/coffee meal conditions; stable and radioisotope methods.\nlimitations: Possible effect modification by poor vitamin A status remained unresolved; beta-carotene was not directly retested.\ncross_nutrient: Vitamin A/iron absorption replication disagreement.\n[va-walczyk2003] No enhancing effect of vitamin A on iron absorption in humans (2003). https://pubmed.ncbi.nlm.nih.gov/12499334/ DOI: 10.1093/ajcn/77.1.144","model_system":"Water/coffee meal conditions; stable and radioisotope methods.","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [va-walczyk2003] No enhancing effect of vitamin A on iron absorption in humans (2003). https://pubmed.ncbi.nlm.nih.gov/12499334/ DOI: 10.1093/ajcn/77.1.144","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"0c5474e2-be48-547b-b287-9c07a59c9ff1","stable_key":"import-dff9f743-3766-5f20-a71e-d6d2bd5bfb6f","title":"Vitamin A: forms, mechanisms, deficiency and excess (2026-09-17)","document_type":"imported_text","citation_label":"AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. Not publisher full text.","file_path":"","sha256":"b217224b262abbd77d6a0c8c9beefff9c022fae4d31e2a5273915d769b9a6546","revision_id":"61008909-871f-575c-b5e2-21542689ea3c","review_status":"unverified_draft","notes":""}}],"relations":[],"conflicts":[{"id":"6119ee31-043f-5f5b-8e83-9dc4460bf1a8","title":"Does vitamin A enhance nonheme iron absorption from cereal meals?","kind":"contradiction","status":"open","why":"The 1998 human studies reported enhancement; five follow-up experiments explicitly failed to reproduce it. The disagreement concerns direct meal iron absorption, separate from longer-term anemia responses.","resolution":"Unresolved across the tested settings. Compare baseline vitamin A status, meal composition, iron preparation and tracer methods. The follow-up investigated incomplete tracer equilibration without finding that it explained the earlier positive result. It did not directly retest beta-carotene.","created_at":"2026-09-17 09:38:26","record_type":"conflict","display_label":"Recorded conflict","record_url":"/conflicts/6119ee31-043f-5f5b-8e83-9dc4460bf1a8","sides":[{"conflict_id":"6119ee31-043f-5f5b-8e83-9dc4460bf1a8","ordinal":0,"label":"Reported enhancement with vitamin A/carotene","revision_id":"61008909-871f-575c-b5e2-21542689ea3c","start_line":1542,"end_line":1552,"quote":"### va-iron-absorption-positive1998\nVitamin A and beta-carotene increased labelled nonheme iron absorption from tested cereal meals.\nCondition category: normal\nnutrient_topic: Vitamin A research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: This study found that the meal additives made more iron available.\norganism: Homo sapiens\ntissue_or_cell_type: Intestinal absorption\nexperimental_model: Six human cereal-meal studies.\nlimitations: Not consistently replicated; the claimed iron-complex mechanism was proposed rather than structurally demonstrated.\ncross_nutrient: Vitamin A/carotene -> iron absorption; contested.\n[va-garciacasal1998] Vitamin A and beta-carotene can improve nonheme iron absorption from rice, wheat and corn by humans (1998). https://pubmed.ncbi.nlm.nih.gov/9482776/ DOI: 10.1093/jn/128.3.646","source_key":"import-dff9f743-3766-5f20-a71e-d6d2bd5bfb6f","source_title":"Vitamin A: forms, mechanisms, deficiency and excess (2026-09-17)","claim_ids":["6110776c-e8ce-5eb6-9a79-4c0e3dab68f7"]},{"conflict_id":"6119ee31-043f-5f5b-8e83-9dc4460bf1a8","ordinal":1,"label":"Retinyl-palmitate enhancement not reproduced","revision_id":"61008909-871f-575c-b5e2-21542689ea3c","start_line":1566,"end_line":1576,"quote":"### va-iron-absorption-no-enhancement2003\nFive isotope studies did not confirm enhanced iron absorption after adding retinyl palmitate to corn-bread meals.\nCondition category: normal\nnutrient_topic: Vitamin A research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: Follow-up experiments did not reproduce the earlier positive result.\norganism: Homo sapiens\ntissue_or_cell_type: Intestinal absorption\nexperimental_model: Water/coffee meal conditions; stable and radioisotope methods.\nlimitations: Possible effect modification by poor vitamin A status remained unresolved; beta-carotene was not directly retested.\ncross_nutrient: Vitamin A/iron absorption replication disagreement.\n[va-walczyk2003] No enhancing effect of vitamin A on iron absorption in humans (2003). https://pubmed.ncbi.nlm.nih.gov/12499334/ DOI: 10.1093/ajcn/77.1.144","source_key":"import-dff9f743-3766-5f20-a71e-d6d2bd5bfb6f","source_title":"Vitamin A: forms, mechanisms, deficiency and excess (2026-09-17)","claim_ids":["399c1c74-8848-50b3-aa66-567b38797576"]}]}],"corrections":[],"research":null}