Minerals　control　on　the　oral　bioavailability　of　arsenic　(As)　in　soil　has　been　evidenced　in　human　health　risk　assessments.　However,　little　is　known　about　the　metabolism　of　soil　mineral-associated　As　by　human　gut　microbiota.　This　study　evaluated　the　relative　bioavailability　(RBA)　and　bioaccessibility　of　As　in　As(V)-sorbed　Aluminum　(Al)　oxides　(α-Al2O3　and　γ-Al2O3),　affected　by　gut　microbiota　and　Fe(III).　The　in　vitro　method　yielded　higher　As　bioaccessibility　in　the　small　intestinal　phase　of　α-Al2O3　(30.3　%–54.8　%)　and　in　the　colon　phase　of　γ-Al2O3　(29.7　%–45.6　%),　respectively.　In　the　presence　of　Fe,　As　release　was　decreased　by14.5　%–48.1　%　in　the　small　intestine　but　increased　by　37.5　%–86.3　%　in　the　colon　(p　＜　0.05).　Speciation　analysis　revealed　that　gut　microbiota　reduced　nearly　half　of　the　As(V)　to　As(III)　in　the　colon　digests,　with　up　to　21.0　%　of　As(III)　remaining　in　the　solid　phase.　More　than　92.0　%　of　Fe(III)　in　the　colon　digests　was　reduced　to　Fe(II),　which　would　facilitate　As　reduction　but　inhibit　methylation.　A　mouse　bioassay　was　conducted　to　estimate　As-RBA　(21.3　%–58.8　%)　in　Al　oxides,　decreased　by　Fe(III)　addition　under　high　As　exposure.　Our　findings　provide　new　insights　into　the　role　of　Al　oxides　in　the　risk　assessment　from　inadvertent　oral　ingestion　of　As-contaminated　soils.　©　2025　Elsevier　B.V.