In a clinical study involving patients with type 2 diabetes, an almond-based diet with a low-carbohydrate content, which had been previously shown to possess marked prebiotic properties [110, 111], resulted in augmentation of the number of SCFA-producing bacteria species, such as Roseburia, Ruminococcus and Eubacterium, which led to an increase in fasting blood GLP-1 levels and also promoted antidepressive effects after three months [112]. This evidence concerns the gene GCG and type 2 diabetes mellitus.