GSTM1 and anemia (phenotype): Of interest anemia 9/23 (39%) versus 2/30 (7%) (Hb < 11.5 g/dl for women and < 12.6 g/dl for men) and lower mean baseline Hemoglobin (11.3 g/dl vs 13.6 g/dl, p < 0.0004, 95% CI − 3.51 to − 1.08) was present in the cohort found to have no significant gastrointestinal disease on follow up (Table 2).