Catalase (CAT) catalyzes the conversion of H2O2 to water and oxygen. SNPs in the CAT gene promoter region, CAT-844 AA and CAT-262 CT or TT, have been associated with essential hypertension among Chinese157, smoking Russians154, Greeks155, but not African-Americans and Caucasians156. However, CAT haplotype [−844G,−89A,−20T] relative to the CAT haplotype [−844A,−89T,−20C] was predictive of a decrease in diastolic blood pressure after bariatric surgery in a French population378. In individuals with low-level lead exposure, CAT rs769217, C>T, is associated with increased blood markers of oxidative stress and hypertension379. By contrast, CAT rs1049982, −20 C>T, is associated with lower blood pressure230. In individuals with a family history of hypertension, 20-35% of the variation of plasma hydrogen peroxide may be due to genetic factors380, 381.