Cooking vegetables and fruits using high heat, water, or both can destroy some of their nutrients. Here's how to get the most from their nutritional power.
Cooked or raw?
High temperatures can destroy 15 to 30 percent of some of the vitamins in vegetables. Boiling leaches another 10 to 20 percent, and up to 15 percent of minerals. But you can limit those losses by microwaving, sautéing, or steaming. And cooking actually increases the potency of some nutrients by helping to break down the cell walls of the plant. For example, cooking increases the availability of antioxidants in carrots, spinach, and tomatoes.
Still, including some raw produce in your diet expands your options and can help you reach the recommended five to nine daily servings of fruits and vegetables. Raw vegetables can replace potato chips or other caloric fare as snacks. And fresh fruit, especially with a low-fat whipped topping, makes great desserts. Increase your intake of raw vegetables slowly though, since they can cause gas.
Fresh or frozen?
For taste and nutrition, fruits and vegetables fresh from the garden or farm are best. But the "fresh" vegetables most of us eat have been hauled or flown across the country and then displayed for several days in stores, giving plenty of time for air, heat, and light to diminish their vitamin content. Even fruit, which continues to ripen after picking, can lose nutrients by the time you get it to the table. So frozen produce, which is usually flash-frozen soon after picking, can be at least as nutritious. Frozen fruits and vegetables can last for about a year.
Most canned produce doesn't stack up against fresh or frozen, since much of its vitamin content is destroyed by high processing temperatures or lost in the water in the can. And canned fruit is often packed in high-calorie syrup.
Now you are cooking
To maximize healthfulness, follow these tips when buying or cooking vegetables:
Microwave right. Use a microwave-safe dish and just enough water to keep the food from burning (around 1 teaspoon for two servings). Cover with plastic wrap or waxed paper.
Steam, don't boil. If you don't have an electric steamer, get an insert for a regular pot that holds the food above a small amount of boiling water. Save the water to cook rice or add to soup.
Stir-fry. Baking, roasting, and grilling expose food to high temperatures for longer times. Frying does too, though stir-frying cut-up vegetables in a bit of oil can minimize the losses.
Plant a garden. Don't worry if you have minimal space. Herbs, peppers, and tomatoes, for example, can grow in pots as long as they get adequate light.
Choose seasonal produce. Visit farmers' markets when possible to reduce the time from farm to table.
Consider organic. Some organically grown fruits and vegetables, such as apples and tomatoes, appear to have higher amounts of certain nutrients.
Get produce that lasts. Include some less-perishable vegetables, such as cabbage, carrots, and potatoes, in your cart.
Make smoothies. Put fruit or vegetables in a blender with low-fat yogurt or a little juice to make a nutritious drink.