Oh, those leafy greens! They tell you to eat more of them, and for good reason. Leafy greens top the list of nutrient-dense vegetables. No wonder! They’re chock-full of fiber, magnesium, calcium, vitamin C, and B-vitamins, particularly folate. Plus, they contain phytonutrients with anti-inflammatory activity.
But how much nutrition are you getting when you enjoy a freshly cooked bowl of greens? The leafy greens you buy at a farmer’s market may start with a lot of nutrients, but by the time you place them on the table, that may have changed.
Chopping Greens Long Before Eating Them Reduces Their Nutrient Content
When you chop a leafy green, like kale, you break down the cell wall of the plant, and that starts the oxidation process. This increases the rate at which the nutrients degrade. While most minerals maintain their value when exposed to air, vitamins are more sensitive, especially folate and vitamin C.
Dark greens, like kale, also lose their healthful properties more quickly than lighter ones like spinach and lettuce, but darker greens are usually higher in phytonutrients that act as antioxidants than lighter ones. So, it’s smart to pick darker leaves. Leafy greens also lose vitamin C and some B-vitamins in storage, as these vitamins are sensitive to light and heat. As a general guideline, you should eat kale within a day or two of purchasing it.
Cooking Leafy Greens and How It Affects Nutrient Values
Cooking reduces vitamin C, since it’s a heat-sensitive vitamin, but cooking still has benefits. Sauteing greens in olive helps your body absorb more of their fat-soluble nutrients, like beta-carotene. Without a source of fat, you’ll absorb far less beta-carotene. Your body can benefit from beta-carotene since it has anti-inflammatory and antioxidant activity. In addition, a portion of the beta-carotene in fruits and vegetables, including leafy greens, is converted to vitamin A, an antioxidant vitamin.
Cooking also affects the fiber content of vegetables. Boiling causes some loss of fiber while steaming and microwaving preserve most of the fiber. Fiber’s interaction with bile in your digestive tract helps reduce levels of bad cholesterol in your blood, and soluble fiber also helps with blood sugar control. Other benefits arise from the breakdown of phenolic compounds in greens like kale. These compounds play a protective role against inflammation, cancer, and heart disease.
Whatever cooking method you use, keep cooking times short to preserve fiber and nutrients. Steaming or microwaving with a small amount of water works well since the vitamins leach into the water. With less water, you get reduced vitamin loss. The worst method is to boil greens in water, as it leads to significant vitamin loss. If you must boil your vegetables, hang on to the water, since it contains vitamin C and B-vitamins, and use it to make a soup or add it to a smoothie. One advantage of boiling leafy greens is that it reduces the oxalate content of greens, such as spinach. Oxalates reduce the absorption of some minerals and are linked with kidney stones in susceptible individuals.
One method that preserves vitamins is to quickly cook (in an open pan) with a little water to preserve nutrition, or sauté (in a skillet with oil) over medium heat for 5 minutes until wilted.
Some People Are Turned Off by the Bitterness of Leafy Greens
To get any of the nutrients in leafy greens, like kale, you must eat them. Sadly, not everybody loves kale. Some people say their bitterness turns them off. Studies show some are genetically more sensitive to the bitter tones in leafy greens and may have a hard time eating them. However, some types of kale are less bitter. One of them is a raggedy leaf known as Lacinato Kale, which can be served raw in salads, steamed, or sauteed.
Braising greens helps reduce the bitter flavor too, and adding a little lemon juice and salt can further reduce bitterness. Plus, there are a myriad of spices you can add to perk up the flavor of greens and mask the bitterness. Heart-healthy spices like turmeric, ginger, cumin, and garlic will jazz up the flavor of greens and offer anti-inflammatory benefits too.
Raw or Cooked Greens?
There are advantages to eating raw and cooked greens. With raw greens, you get more vitamin C, but you may not absorb as much beta-carotene without a source of fat. If you place leafy greens in a salad, include a healthy source of fat, like avocado or nuts, and use an olive oil-based salad dressing. Any source of fat will boost how much beta-carotene your body absorbs, but olive oil and nuts are among the healthiest fat sources.
Make sure the greens you purchase are fresh. If it’s a little wilted at the store, leave them behind. Never buy slimy greens, have soft spots, or are browning on the edges. If possible, buy local, since they’re less likely to have sat around long enough to lose their vitamins.
The Bottom Line
You lose vitamins when you cook leafy greens, and the cooking method matters. Stick to short cooking times and as little water as possible. Adding a source of fat offers advantages too, since it helps you absorb fat-soluble nutrients, such as beta-carotene. Enjoy them raw too, but don’t let them sit around before munching on them. And remember, the only healthy greens are the ones you eat!
References:
- “Effect of different cooking methods on the content of ….” 12 Dec. 2017, ncbi.nlm.nih.gov/pmc/articles/PMC6049644/.
- “Do Vegetables Lose Nutrients When Cooked? | Livestrong.com.” 03 Sept. 2019, livestrong.com/article/465595-do-vegetables-lose-nutrients-when-cooked/.
- “Leafy Greens to Get to Know – WebMD.” webmd.com/food-recipes/ss/slideshow-know-your-leafy-greens.
- “Effect of different cooking methods on vegetable oxalate ….” pubmed.ncbi.nlm.nih.gov/15826055/.
- Lee S, Choi Y, Jeong HS, Lee J, Sung J. Effect of different cooking methods on the content of vitamins and true retention in selected vegetables. Food Sci Biotechnol. 2017;27(2):333-342. Published 2017 Dec 12. doi:10.1007/s10068-017-0281-1.
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