Dietary cinnamon essential oil improves the amino acids, lipid quality, long‐chain polyunsaturated fatty acid biosynthesis, and gut microbiota of Nile tilapia

BACKGROUND: Cinnamon essential oil (EO) exhibits high antioxidant and antibacterial activities; however, its effects on nutrient deposition and gut microbiota in Nile tilapia remain unclear. This study investigated the effect of dietary cinnamon EO on amino acid (AA) and fatty acid (FA) composition, long-chain polyunsaturated fatty acid (LC-PUFA) metabolism, and gut microbiota of Nile tilapia (Oreochromis niloticus). RESULTS: cinnamon EO for 30 days. Supplementation linearly increased taste-active AAs and essential AAs (P < 0.05). The T3 group exhibited the highest aspartate and serine contents, with 2.3-fold and 5-fold increases compared to the control, respectively. The EO significantly improved the FA composition, with the greatest increase observed for C22:6n3 in the T3 group. Cinnamon EO supplementation improved lipid quality indices (atherogenicity index, thrombogenicity index, hypocholesterolemic index, and nutritive value index; P < 0.05). T3 supplementation significantly upregulated key LC-PUFA biosynthesis genes, including Δ6Δ5 fads2, Δ4 fads2 and elovl5 (P < 0.05). Δ6Δ5 fads2 and Δ4 fads2 mRNA levels were increased 3- and 8-fold, respectively, compared with the control group (P < 0.05). T3 supplementation increased the relative abundance of Firmicutes and Proteobacteria at the phylum level. The unclassified_Planctomycetaceae and unclassified_Rhizobiales abundances were positively correlated with the mRNA levels of Δ4 fads2 and elovl5 (0.997, 0.994. P < 0.01). CONCLUSION: Dietary cinnamon EO improved AA and FA composition and enhanced LC-PUFA biosynthesis, which was associated with alterations in gut microbiota. © 2026 Society of Chemical Industry.