Cooking vegetables can loosen their cell walls, making it easier for your body to absorb their nutrients. But leaving them in the oven or on the stove for too long can have the opposite effect, says Bethany Snodgrass, holistic health coach and operations manager at the Equinox Fitness Training Institute in New York City.
“Exposure to heat changes the chemical structure of foods,” Snodgrass explains. For many vegetables, cooking actually boosts their vitamins and minerals. Cooked red cabbage, for example, has a 270 percent higher antioxidant level than it does when raw, she says—but only if it’s cooked correctly. Heat loosens and re-hydrates vegetable fibers, which makes it easier for your body to break down and access the nutrients. Once the temperature reaches 300 degrees F, though, cooking starts to destroy beneficial amino acids.
The bottom line
You can roast vegetables below 300 degrees, but Snodgrass says you’ll preserve the most nutrients by lightly steaming or boiling them. Stop cooking them when they’re vibrant in color, with some give on the outside but still firm on the inside, Snodgrass says. Crunchy vegetables, like carrots, should still snap when you break them, even after cooking.