Health researchers have determined that increased consumption of fruits and vegetables leads to reduced risk of heart disease and cancer. Nutritionists at the National Cancer Institute and other health professionals recommend eating at least five servings of fruits and vegetables a day. Snap beans are a fair source of Vitamins A and C, calcium, iron, and potassium.
Beans should be light yellow in color or green; firm and crisp in texture; and smooth with no evidence of seeds bulging. Avoid beans with flabby, tough pods and bulging seeds. Boiling or steaming fresh beans in water kills many food-borne, illness-causing organisms that may be present. This is a viable option for individuals who are especially susceptible to these organisms (immune compromised persons and young children) to reduce their potential risk.
This is a great article on the nutritional value of beans of all kinds, along with a guide on what to know when cooking and storing beans. It also tells you what to be aware of when preserving beans by canning.