Moreover, a Taiwanese study on periodontal disease and f-Hb concentrations reported that participants with a concentration of ≥20.0 μg Hb/g faeces had a 33.0% higher risk of their periodontal disease deteriorating to severe when compared to those with f-Hb concentrations <20.0 μg Hb/g faeces [36]. This evidence concerns the gene GSTM1 and periodontal disorder.