Green beans are a healthy food. They are low in calories, fat and sugar and high in vitamin C, vitamin K and manganese. They also provide potassium, magnesium, iron, vitamin A and dietary fiber.
Green beans maintain their nutritional content through freezing and cooking. To maintain optimal nutritional value, green beans should be frozen for a maximum of 6 months. Steaming green beans preserves more vitamins and minerals than other forms of cooking, but they can also be served boiled, baked or fried.
Raw green beans are not harmful in small quantities, but must be eaten in moderation. Green beans contain compounds called lectins, which are toxic in large quantities. Cooking green beans destroys the lectins and renders the beans safe to eat. Another health concern associated with green beans is the presence of oxalates, which can crystallize and exacerbate existing kidney and gallbladder problems. Oxalates are not destroyed by cooking, but they do not pose a problem for people with healthy kidney and gallbladder function.
Green beans are closely related to kidney, navy and black beans. These plants are native to Central and South America; their spread to Europe and Asia occurred thanks to 16th-century Spanish and Portuguese explorers.