Vegetables provide significant amounts of fiber, vitamins, minerals and beneficial plant chemicals without containing a lot of calories, making them a good way to meet your nutrient needs. Whether you eat your vegetables raw or cooked, and the cooking method you use, can affect their nutritional value, but both raw and cooked vegetables are nutritious.
Cooking your vegetables can destroy some of the nutrients, especially if you cook them in water. You'll lose up to 30 percent of the amount of vitamins when cooking vegetables and, if you cook them in water, up to another 20 percent of vitamins and up to 15 percent of water-soluble minerals, notes the Consumer Reports website. Some of the nutrients most sensitive to cooking include potassium, vitamin C, folate and thiamine. You'll lose fewer nutrients if you microwave or steam your vegetables instead of boiling, baking, roasting, frying or sauteing them.
Cooking actually increases the availability of some nutrients, including vitamin A, calcium, iron and the antioxidant lycopene. The cell walls of the vegetables break down during cooking, making it easier for your body to absorb these nutrients. Also, some vegetables, such as spinach, shrink in size when cooked, so when you eat them cooked you get more nutrients from a cup of the vegetable than you would if you ate a cup of the same vegetable raw, even accounting for nutrient losses, notes the University of Florida Extension.
Eating more fruits and vegetables, both raw and cooked, may help lower your risk for certain types of cancer, according to a review article published in "Cancer Epidemiology, Biomarkers & Prevention" in September 2004. The evidence is stronger for raw vegetables than for cooked vegetables, however, in part because some of the nutrients that help prevent cancer are destroyed during the cooking process. For example, a beneficial plant chemical called myrosinase, which helps break down substances in broccoli to form isothiocyanates, a compound that helps prevent cancer, is destroyed by cooking. This causes cooked broccoli to have about two-thirds fewer isothiocyanates than raw broccoli, according to a study published in "Nutrition and Cancer" in 2000.
Vegetables can sometimes be contaminated with bacteria or other substances that can cause food-borne illnesses. Cooking destroys many of these substances, making cooked vegetables safer than raw from a food-safety standpoint, especially for people with compromised immune systems. Refrigerating raw produce, keeping it separate from meat and poultry and items that have touched these foods and washing your produce before you eat it can decrease the risk of food poisoning from raw vegetables.