AIM:To perform a meta-analysis of observational studies and randomized controlled trials(RCTs)on the association between Helicobacter pylori(H.pylori)and iron deficiency anemia(IDA).METHODS:A defined search strategy was used to search Medline,Embase,the Cochrane Library,Clinical Trials,Cochrane Central Register of Controlled Trials,Premedline and Healthstar.Odds ratio(OR)was used to evaluate observational epidemiology studies,and weighted mean difference(WMD)was used to demonstrate the difference between control and intervention groups.RESULTS:Fifteen observational studies and 5 RCTs were identified and used for calculation.The pooled OR for observational studies was 2.22(95%CI:1.52-3.24,P<0.0001).The WMD for hemoglobin(HB) was 4.06 g/L(95%CI:-2.57-10.69,P=0.01),and the WMD for serum ferritin(SF)was 9.47μg/L(95%CI:-0.50-19.43,P<0.0001).Results were heterogeneous for all comparisons.CONCLUSION:This meta-analysis on observational studies suggests an association between H.pylori and IDA.In RCTs,eradication of H.pylori can improve HB and SF levels but not significantly. AIM: To perform a meta-analysis of observational studies and randomized controlled trials (RCTs) on the association between Helicobacter pylori (H. pylori) and iron deficiency anemia (IDA). METHODS: A defined search strategy was used to search Medline, Embase , the Cochrane Library, Clinical Trials, Cochrane Central Register of Controlled Trials, Premedline and Healthstar. Odds ratio (OR) was used to evaluate observational epidemiology studies, and weighted mean difference (WMD) was used to demonstrate the difference between control and intervention groups .RESULTS: Fifteen observational studies and 5 RCTs were identified and used for calculation. The pooled OR for observational studies was 2.22 (95% CI: 1.52-3.24, P <0.0001). WMD for hemoglobin (HB) was 4.06 g / L (95% CI: -2.57-10.69, P = 0.01) and the WMD for serum ferritin (SF) was 9.47 μg / L (95% CI: -0.50-19.43, P <0.0001). Results were heterogeneous for all comparisons .CONCLUSION: This meta-analysis on observational studies suggests an association between H.pylori and IDA. In RCTs, eradication of H. pylori can improve HB and SF levels but not significantly.