Prior to bone marrow transplantation adverse reactions to myeloablative drugs can lead to decreased appetite taste salivary gland function gastric emptying and intestinal function in patients as well as severe mucosal inflammation and graft versus host disease GVHD leading to secondary malnutrition. GVHD can directly damage organs and tissues such as the skin liver mucosa lungs esophagus and musculoskeletal system. Long term use of immunosuppressants to prevent and treat GVHD can lead to endocrine and metabolic system diseases including insulin resistance abnormal lipid metabolism hypothyroidism or hypogonadism resulting in malnutrition. Patients with pre-existing malnutrition before transplantation can sustain malnutrition for several years after receiving allogeneic bone marrow transplantation. Improving the nutritional status of patients through nutritional therapy can not only reduce the incidence of acute GVHD in transplant patients shorten implantation time but also reduce infection related mortality and prolong survival.