Objective To investigate the clinical effect of early use of enteral nutrition therapy in elderly diabetic patients suffering from severe lower respiratory tract infection.Methods A prospective,randomized,open,controlled trial was conducted.Patients aged ≥ 60 years old with diabetes mellitus complicated by severe lower respiratory tract infection admitted to Department of Geriatrics of the Ninth People's Hospital Affiliated to Shanghai Jiaotong University School of Medicine from July 2013 to June 2015 were enrolled,and they were divided into the observation group (nasogastric tube infusion of fresubin) and control group (ordinary liquid diet) according to the random number table method,with 60 patients in each group.Nutritional status,inflammation state and immunological indexes before treatment (0 day) and 4,7,14 days after treatment,the outcome of the disease and the nutrition related complications were compared between two groups.Results After treatment,serum albumin (ALB),pro-albumin (PA),immunoglobulin A and G (IgA,IgG) were significantly increased compared with those before treatment in both groups [at 7 days,ALB (g/L):28.37 ± 0.40 vs.26.72 ± 0.37 in control group,29.12 ± 0.25 vs.26.86 ± 0.26 in observation group;PA (mg/L):53.80 ± 6.28 vs.43.76 ± 6.93 in control group,58.46 ± 8.70 vs.44.68 ± 7.33 in observation group;IgG (g/L):11.62±4.72 vs.9.98±3.71 in control group,13.36±4.58 vs.9.88±3.27 in observation group;IgA (g/L):2.31 ±0.35 vs.1.50±0.39 in control group,3.07±0.48 vs.1.37±0.29 in observation group;all P ＜ 0.05].Compared with the control group,the level of PA in observation group was significantly increased from 7 days on (mg/L:58.46 ± 8.70 vs.53.80 ± 6.28,P ＜ 0.05),while ALB,IgG,IgA levels in observation group increased at 14 days [ALB (g/L):33.24 ± 0.45 vs.30.76±0.79,IgG (g/L):15.03 ±3.73 vs.11.45 ±2.83,IgA (g/L):3.56±0.32 vs.2.50±0.16,all P ＜ 0.05].The levels of C-reactive protein (CRP) and procalcitonin (PCT) in both groups gradually lowered,but they were significantly lower in observation group than those in the control group from 4 days on [CRP (mg/L):17.72±4.23 vs.20.96±5.83,PCT (ng/L):123±37 vs.257±88,both P ＜ 0.05],up to 14 days.The hospital mortality rate of the observation group was lowered compared with that of the control group (6.67％ vs.8.89％),and the duration of mechanical ventilation was significantly shortened (hours:145.00±19.39 vs.193.00± 18.97,P ＜ 0.05),insulin dosage was also significantly decreased (U:33.52 ± 5.74 vs.49.71 ± 6.99,P ＜ 0.05).There was no significant difference in the incidence of abdominal distension,diarrhea and reflux of gastric contents between the two groups,and they were relieved after treatment and had no influence on further enteral nutrition therapy.Conclusion Early administration of the complicated enteral nutrition in elderly diabetic patients with severe lower respiratory tract infection cannot only decrease the levels of pro-inflammatory factors in patients,but also shorten the duration of mechanical ventilation,enhance immunity,improve the curative effect with little influence on the blood glucose level.