Cooking vegetables can release nutrients and boost antioxidant capabilities
Maximize nutrition by matching the cooking method to the vegetable
Good defaults are steaming and microwaving
Whether you love vegetables or not, there’s one thing you know for sure: Veggies are really good for you. And you can make them even more nutritious if you prepare them in ways that maximize their benefits.
Oddly enough, that’s not likely to be raw. Studies show the process of cooking actually breaks down tough outer layers and cellular structure of many vegetables, making it easier for your body to absorb their nutrients.
For example, compared to raw, “studies found that eating cooked spinach and carrots resulted in higher blood levels of the antioxidant beta carotene, which then converts to vitamin A,” said registered dietitian Elaine Magee, author of “Food Synergy: Unleash Hundreds of Powerful Healing Food Combinations to Fight Disease and Live Well.”
And it’s not just limited to vitamins, Magee said. “Cooking vegetables also helps increase the amount of minerals, like calcium, magnesium and iron, available to the body,” she said.
Steam, don’t boil
As a general rule, it’s best to keep cooking time, temperature and the amount of liquid to a minimum. That’s why steaming is one of the best ways to cook most vegetables. It turns out that’s especially true for broccoli, long touted as one of our top anti-cancer foods.
“When buying fresh broccoli, look for firm florets with a purple, dark green, or bluish hue on the top,” Magee said. “as they are likely to contain more beta carotene and vitamin C than florets with lighter green tops.”
A 2009 study prepared broccoli using five popular methods – boiling, microwaving, steaming, stir-frying and stir-frying/boiling. Researchers found steaming kept the highest level of nutrients.
“Boiling vegetables causes water soluble vitamins like vitamin C, B1 and folate to leach into the water,” Magee said. “So unless you are going to drink the water along with your vegetables, such as when making soups and stews, these vitamins are typically poured down the sink. Steaming is a gentler way to cook because the vegetables don’t come in contact with the boiling water.”
Another 2009 study found peas, cauliflower and zucchini to be particularly susceptible to a loss of nutrients through boiling, losing more than 50% of their antioxidants. “Water is not the cook’s best friend when it comes to preparing vegetables,” the researchers summarized.
But what’s a rule without exceptions? In this case, it’s carrots. Another study showed both boiling and steaming increased levels of beta carotene. But try to cook carrots whole, as cutting can reduce nutrients by 25%.
In fact, cooking veggies whole is often the best choice to preserve nutrients. When that’s not practical, be sure to cut them into large uniform pieces that will cook evenly. And wait to wash your vegetables until just before you cut – washing before storing may promote bacterial growth and speed up spoilage, Magee said.
When in doubt, microwave
Microwaving uses little to no water, and can heat the veggie quickly from within, preserving nutrients such as vitamin C that break down when heated. A 2003 study found significantly higher levels of phytonutrients in zucchini, carrots and beans cooked with minimal water. Phytonutrients are compounds naturally found in plants that provide health benefits and disease protection in the human body.
Another exception: Don’t microwave cauliflower. The 2009 Spanish study found the highest losses of nutrients in cauliflower after boiling and microwaving.
Saute, don’t fry
Studies show that during deep-fat frying, fat penetrates the food and vegetables dehydrate. But sauteing in a bit of healthy cooking oil, such as extra-virgin olive oil, is a great way to cook many vegetables. Not only does it maximize flavor, but the addition of olive oil “appears to increase the absorption of phytonutrients like phenols and carotenes,” said Magee, who is also the corporate dietitian for the grocery firm Albertsons Companies. That’s because many of the vitamins and nutrients in vegetables are fat soluble, meaning your body absorbs them better in the presence of fat.