Probiotic supplementation in PD patients has been shown to improve stool consistency and reduce bloating and abdominal pain (Cassani et al., 2011; Barichella et al., 2016; Knudsen et al., 2017; Dutta et al., 2019; Gazerani, 2019; Srivastav et al., 2019; Castelli et al., 2021; Tan et al., 2021a), improve the MDS-UPDRS (Movement Disorders Society-Unified Parkinson’s Disease Rating Scale) and insulin metabolism (Tamtaji et al., 2019). This evidence concerns the gene INS and Parkinson disease.