There is possible evidence that eating fruit and vegetables can help lower the risk of developing asthma or COPD, but note that this is based on relatively few studies; more research needs to be done to definitively answer this question.
To prevent or manage heart disease: focus on fruit, vegetables, whole grains, seafood, beans, eggs, nuts, seeds, poultry, lean meats, low-fat dairy. Limit fried foods, bacon, cheese, sweets like pies, cakes, cookies, donuts, candy. The risk of heart disease can also be reduced by maintaining a healthy weight. For more assistance about your diet, ask your doctor to refer you to a registered dietitian, or find one in your area by searching EatRight.org.