Kristie Leong M.D. is a family practitioner with a strong background in nutrition.
What Is Kale?
Kale is a leafy green vegetable packed with vitamins and minerals, fiber, antioxidants, and other nutrients. It's also one of the healthiest vegetables you can eat—one cup of chopped kale provides about 2.5 grams of protein and 2.6 grams of fiber along with plenty of vitamin’s A, C, B6, and K. Plus, it’s rich in calcium and potassium.
Leafy greens, like kale, are a versatile food, you can enjoy as a main course or side dish, in soups and salads, and even for breakfast. Why not add kale to an omelet or your breakfast burrito? But if you notice your kale has turned yellow, you might wonder if it's still safe to eat or if you should toss it.
What It Means When Kale Turns Yellow
If you look at a bunch of kale, you might notice the stems and leaves are no longer a rich green shade. Instead, they have turned yellow. You may even see bunches of kale in the grocery store that have yellowing of their leaves and stems.
Yellowing is a sign that chlorophyll, the pigment that gives leafy greens their green coloration is breaking down. But don't let it scare you. It's simply a sign that your leafy kale is getting older and is no longer in its prime.
Yellow Kale Is Aging Kale
From a health standpoint, the color change doesn't mean that kale is unsafe to eat. It means the kale is no longer fresh and vibrant, as it was right after harvest. You can still safely cook kale that has turned yellow.
You should also inspect the kale closely and look for other signs of spoiling such as moldy areas. One sign of mold growth is black spots on the leaves. If you see blackened areas, it's safest to discard kale.
Also, ensure the kale you're about to cook or eat doesn't have a strong odor. Kale normally has a faint earthy aroma. As kale rots, it releases a sulfur aroma that mimics rotten eggs. If you notice an odor, toss it. Unpleasant smells are a sign you should discard a vegetable.
How Yellowing Affects Its Taste
As leafy greens, like kale, age, their flavor can degrade, too. So, you may not get the same satisfaction from cooking and eating yellow kale as you would a fresher batch.
However, if you cook yellowed kale with a sauce, it should improve its taste and you’ll still get the fiber, vitamins, and minerals that kale is famous for.
If you add a source of healthy fat to kale, like olive oil, it will enhance the amount of beta-carotene (a precursor to vitamin A) that you absorb from the vegetable.
Kale Is a Nutrient-Dense Food
Kale is also a good source of antioxidants and compounds with anti-inflammatory activity. However, a study found that cooking kale reduces its antioxidant activity by decreasing the quantity of vitamin C (antioxidant vitamin), beta-carotene (an antioxidant and precursor to vitamin A), and polyphenols, other antioxidant compounds with anti-inflammatory activity. Therefore, raw kale has a nutritional edge over cooked kale.
Cooking Kale That Has Turned Yellow
Kale that has yellowed isn’t harmful to cook or eat, as long as it shows no signs of rotting, such as black spots and a strong odor. If the kale is also wilted, it may have lost a significant quantity of nutrients but is still edible. Since older kale isn’t as tasty, cooking it in a tasty source can make it more enjoyable. Any way you eat it, kale is a nutrient-dense food that deserves a place on your plate. Enjoy!
- "10 Health Benefits of Kale." 29 Jun. 2018, https://www.healthline.com/nutrition/10-proven-benefits-of-kale.
- "Kale | The Nutrition Source | Harvard T.H. Chan School of Public Health." https://www.hsph.harvard.edu/nutritionsource/food-features/kale/.
- Sikora E, Bodziarczyk I. Composition and antioxidant activity of kale (Brassica oleracea L. var. acephala) raw and cooked. Acta Sci Pol Technol Aliment. 2012 Jul-Sep;11(3):239-48. PMID: 22744944.
- Ribaya-Mercado JD. Influence of dietary fat on beta-carotene absorption and bioconversion into vitamin A. Nutr Rev. 2002 Apr;60(4):104-10. doi: 10.1301/00296640260085831. PMID: 12002680.
- "Beta Carotene: Benefits, Foods to Eat, and More - Healthline." 13 Aug. 2020, https://www.healthline.com/health/beta-carotene-benefits.
- "Kale, cooked, boiled, drained, without salt Nutrition Facts ... - Self." https://nutritiondata.self.com/facts/vegetables-and-vegetable-products/2462/2.