Inclusion Criteria:  History of known coronary artery disease as defined by having one or more of the following:  history of myocardial infarction angiogram demonstrative >=50% stenosis in at least 1 major epicardial coronary artery a previous stress test that showed evidence of ischemia (that has not been revealed to be a false positive test by angiography) CT coronary study showing EITHER a coronary artery calcium (CAC) score of >400, OR a description of "significant stenosis" of one or more epicardial arteries.  Exclusion Criteria:  Unstable angina or myocardial infarction by history, ECG, and/or enzymatic criteria within 1 month of enrollment. LV dysfunction as defined by an LV ejection fraction documented as < 45% within 1 year of enrollment by an echocardiogram, MRI, or nuclear imaging. Uncontrolled hypertension with a blood pressure greater than 170/100 mmHg at the screening visit. Known history of chronic renal insufficiency, liver dysfunction, or cancer besides non-melanoma skin carcinomas or localized prostate cancer requiring systemic treatment within five years of enrollment. Known history of cognitive impairment or inability to follow study procedures. Patient with GI tract illness such as short gut syndrome, inflammatory bowel disease, or an ileostomy. Patient with an implanted defibrillator or permanent pacemaker on which the potential participant is known to rely upon for greater than 50% of ventricular depolarizations. Patients who received probiotics, prebiotics, or short chain fatty acid supplements (e.g. propionate, butyrate, acetate-containing supplements) within the past 4 weeks. Patients who received antibiotics in the last 12 weeks. Patients with dosing changes of vasoactive medications and HMG-CoA reductase inhibitors in the 6 weeks prior to enrollment. Pregnancy Those who are daily drinkers or use illicit drugs.