我国恶性肿瘤的发病率和死亡率呈逐年上升趋势。恶性肿瘤，尤其是胃肠道肿瘤的发生和发展与肠道微环境失 调即肠道微生物紊乱密切相关；脂肪酸尤其是必需脂肪酸是人体生长发育及维持生命过程的重要营养物质，肠道微生物介 导胃肠道消化和吸收脂肪酸。脂代谢失调和肠道微生物作用密切关联，引发胃肠道炎症，导致肠道通透性增加，毒素进入 体内，最终产生免疫反应。肠道微生物群通过病原微生物和肿瘤抗原之间的交叉反应，形成T细胞储备和（或）微生物产品， 刺激模式识别受体，从而影响免疫反应的类型和强度。通过对免疫的影响， 微生物群有助于对远处肿瘤的免疫控制或逃逸。 微生物源性代谢产物也可以通过直接细胞自主致癌机制来促进局部肿瘤的发展。恶性肿瘤的防治过程中，应重视脂肪酸营 养和肠道微环境的重要作用。脂肪酸也可以根据患者的需要通过肠外通路提供。晚期恶性肿瘤患者往往伴有营养不良或异 质性。补充ω-3 多不饱和脂肪酸可以改善患者的体质，有助于肿瘤的治疗。通过补充益生菌或移植肠道微生物群，可以矫 正肠道微生物群紊乱，在肿瘤的防治中发挥重要作用。

The incidence and mortality rate of malignant tumors in China are increasing year by year. The occurrence and development of malignant tumors, especially gastrointestinal tumors, are closely related to disorder of intestinal microenvironment. Fatty acids, especially essential fatty acids, are important nutrients for human growth and life support. Fatty acids are actively involved in the intestinal microbiota during digestion and absorption in the gastrointestinal tract. Disorders of fat metabolism are closely related to the intestinal microbiota, and are associated with gastrointestinal inflammation, increased permeability of intestinal wall and the entry of toxins into the body, to resulted in an immune response. Intestinal microbiota, through cross-reactions between pathogenic microorganisms and tumor antigens, form a T-cell reserve and/or microbial product that stimulates pattern recognition receptors, affect the type and intensity of the immune response. Through the effects on immunity, microbiota help to control of or escape from the immune response to distant tumors. Microbial-derived metabolites can also promote the development of local tumors through direct cell-independent carcinogenesis. There is a relationship between the intestinal microbiota-gut-brain axis or the microbial-intestinal-liver axis with the external organs of the gastrointestinal tract. The important role of fatty acid nutrition and intestinal microenvironment should be taken into account in the prevention and treatment of malignant tumor. Fatty acids may also be given through the parenteral pathway, depending on the patient's needs. Patients with advanced malignant tumors are often accompanied by malnourishment or heterogeneity. Supplementation of ω -3 polyunsaturated fatty acids can improve the physique of patients and contribute to the treatment of tumors. By supplementing probiotics or transplanting intestinal microbiota, the disorders of intestinal micriobiota can be fixed and play an important role in the prevention and treatment of tumor.