**Study Summary**: This study is checking how a vegetarian diet affects the body's natural defense (innate immunity) in people who recently had a heart attack (called a myocardial infarction) and in healthy people. A myocardial infarction happens when blood flow to the heart is blocked, and it can be a serious health issue. Participants will try a vegetarian diet for five weeks, then go back to their regular diet for six weeks, and then switch diets again for five more weeks. Blood tests will be done during the study to see changes in inflammation, which is how the body responds to injury or illness. **Key Points**: - **Duration**: The study lasts about three months, with two main diet phases and a stabilizing period. - **Participation**: Both heart attack patients and their healthy partners can join, but they can't already be on a vegetarian diet or have certain health conditions. - **Incentives**: Participants will receive blood tests and questionnaires to track health changes, but the document does not mention specific compensation.

Note: Some people may not be eligible due to health conditions like diabetes or previous heart attacks.