Kale is a leafy green beloved for its sturdy texture and earthy flavor, but it also contains oxalates—naturally occurring compounds that can contribute to kidney stone formation in sensitive individuals. The good news is that cooking methods like boiling and steaming can significantly reduce kale’s oxalate content, making it gentler on your system while keeping it delicious. This guide explains exactly how to prepare kale to lower its oxalates, with a simple recipe and practical tips you can use right away.
Ingredients
- 1 bunch (about 12 oz / 340 g) fresh kale, any variety (curly, lacinato, or red)
- 4 cups (960 ml) water, for boiling
- 1 tablespoon (15 ml) olive oil (optional, for serving)
- 1 clove garlic, minced (optional)
- 1/4 teaspoon salt, or to taste
- 1 tablespoon (15 ml) lemon juice (optional, for serving)
Instructions
- Rinse the kale thoroughly under cold running water to remove any grit or dirt. Pat dry with a clean towel.
- Strip the leaves from the tough central stems by holding the stem at the base and pulling upward along the leaf with your other hand. Discard the stems (or save them for stock). Tear or chop the leaves into bite-sized pieces.
- Bring 4 cups (960 ml) of water to a rolling boil in a large pot over high heat. Add the kale pieces and stir gently to submerge them.
- Boil the kale for 3 to 5 minutes, until the leaves are tender but still bright green. Do not overcook, or the texture will become mushy.
- Drain the kale in a colander. For maximum oxalate reduction, discard the cooking water—oxalates leach into the water, so do not reuse it for soups or sauces.
- If desired, heat the olive oil in a skillet over medium heat and sauté the garlic for 30 seconds until fragrant. Add the drained kale and toss for 1–2 minutes to coat. Season with salt and lemon juice if using.
- Serve warm as a side dish, or use in salads, grain bowls, or pasta.
Tips
- Boiling beats steaming: Boiling in a large volume of water removes more oxalates than steaming, because the water carries them away. If you prefer steaming, know that it reduces oxalates less effectively—about half as much as boiling.
- Don’t reuse the cooking water: The water you boil kale in contains the leached oxalates. Discard it; using it for broth or cooking grains will reintroduce the oxalates.
- Pair with calcium-rich foods: Calcium binds to oxalates in the digestive tract, reducing absorption. Serve kale with yogurt, cheese, tahini, or almonds to lower the amount of oxalate your body takes in.
- Choose younger leaves: Baby kale and smaller leaves tend to have lower oxalate content than mature, dark leaves. If you’re sensitive, opt for baby kale or mix it with other low-oxalate greens like arugula or butter lettuce.
Serving Suggestions
This boiled kale works as a simple side for grilled chicken, fish, or tofu. Toss it with cooked quinoa, cherry tomatoes, and feta for a grain bowl, or fold it into scrambled eggs. For a warm salad, dress it with olive oil, lemon zest, and toasted pine nuts.
Variations
- Sautéed with spices: After boiling, sauté the kale with cumin seeds, red pepper flakes, and a splash of coconut milk for an Indian-inspired dish.
- Asian-style: Dress the boiled kale with soy sauce, sesame oil, rice vinegar, and a sprinkle of sesame seeds.
- Kale pesto: Blend boiled, drained kale with basil, garlic, pine nuts, Parmesan, and olive oil for a lower-oxalate pesto.
- Creamed kale: Stir boiled kale into a simple béchamel sauce with nutmeg for a comforting side.
Storage and Reheating
Store cooked kale in an airtight container in the refrigerator for up to 3–4 days. To reheat, warm it in a skillet over medium heat for 2–3 minutes, or microwave in 30-second bursts until hot. You can also freeze cooked kale for up to 3 months; thaw overnight in the fridge and reheat gently. The texture will soften further, so it’s best for soups or stews after freezing.
Frequently Asked Questions
Does cooking kale remove all oxalates? No, cooking reduces oxalates but doesn’t eliminate them entirely. Boiling in a large amount of water can remove about 30–50% of the oxalates, depending on the variety and cooking time. The remaining oxalates are still present, so if you are highly sensitive, moderate your portions.
Is raw kale higher in oxalates than cooked? Yes, raw kale contains more oxalates than cooked. For example, a cup of raw kale has about 20 mg of oxalates, while a cup of boiled kale has roughly 8–10 mg. So cooking is a simple way to cut your intake.
Can I drink the water I boiled kale in? No, you should discard the cooking water. It contains the oxalates that leached out of the leaves, so drinking it would reintroduce them. Use fresh water for other cooking.
Is kale high in oxalates compared to spinach? Kale is actually lower in oxalates than spinach. Spinach is extremely high (about 750 mg per cup raw), while kale is moderate (about 20 mg per cup raw). So kale is a better choice for people watching oxalate intake, especially when cooked.
Does adding calcium to kale help reduce oxalate absorption? Yes, consuming calcium-rich foods alongside high-oxalate foods helps bind oxalates in the gut, reducing the amount absorbed into the bloodstream. This can lower the risk of kidney stone formation.
Can I eat kale if I have kidney stones? Many kidney stones are calcium oxalate, so reducing oxalate intake is often recommended. Cooking kale to lower its oxalate content and pairing it with calcium-rich foods can make it safer, but consult your doctor or dietitian for personal advice, as stone types vary.
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Safety notes: safe minimum internal temperatures from USDA FSIS; raw and undercooked fish guidance from the U.S. FDA. Food safety notes
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