 The control group will be selected to represent an age, sex and cardiovascular risk factors -matched group without current CAD. Further exclusion criteria in the control group will be antibiotic consumption in the following 3 months, inflammatory bowel disease, or other significant chronic disease that may influence the microbiota such as cancer, autoimmune disease, and chronic immunosuppressive treatment. The control group will undergo cardiac CT or coronary angiography according to clinical suspicion in order to rule-out CAD and irrespective of the study protocol. 