I'm concerned that I may be overcooking vegetables, and that I'm not getting the needed nutrition. Does a raw food diet give me that much more in the way of micronutrients from food? .
Cooking vegetables--especially overcooking them--can reduce levels of both fat-soluble (A, E, K, and D) and water-soluble (B and C) vitamins.
But despite the potential loss of some vitamins during the cooking process, certain nutrients actually become more available to your body after you cook them.
For example, your body absorbs more lycopene, an antioxidant found in tomatoes, from cooked and processed (e.g. tomato paste, salsa, etc.) products compared to fresh tomatoes. Cooking or the grinding and chopping that happens during the processing of tomatoes breaks down cell walls, making it easier for your body to access lycopene during digestion.
What's more, steaming collard greens, kale, mustard greens, broccoli, green bell peppers, and cabbage improves their ability to "bind" bile acids during digestion, which can help clear toxic metabolites.
Bad News About Boiling
The one cooking method to avoid is boiling, which tends to leach the nutrients out of food. For example, steaming spinach can lead to a 60-percent reduction in vitamin C. And microwaving broccoli in boiling water for 5 minutes has been shown to reduce vitamin C levels and antioxidant activity both by 65 percent. The one exception to my "Don't boil!" rule concerns potatoes, which retain the same amount of vitamins C and B whether boiled or steamed.
Steaming vegetables in the microwave is convenient--just make sure you're steaming and not boiling them. Use only 1 to 3 tablespoons of water in a wide bowl or plate, add the vegetables, and cover tightly with plastic wrap. Pierce the plastic wrap to make a small slit to let out steam. This will ensure that you maximize the steam effect and don't boil your vegetables in water.
Aim to eat a variety of vegetables in a variety of different ways. Eat spinach raw in salads to maximize the amount of vitamin C you'll eat, but also have steamed or sautéed spinach in an omelet or with a piece of salmon. Steamed or sautéed spinach won't have as much vitamin C, but cooking spinach breaks down compounds, called oxalates, that prevent your body from absorbing the calcium in spinach.
Just as you wouldn't stick to one weight-training routine, day in and day out, you shouldn't stick to one way of eating your vegetables, either.