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In this article:
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Kale is one of several kinds of produce with high levels of oxalic acid.
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When oxalic acid and calcium combine in the urine, it can create kidney stones.
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Talk to your Swedish doctor to find out if you could be at high risk for developing kidney stones.
Explore the truth about kale’s role in kidney stone development
You may be astonished to learn that such a healthy food could lead to such an uncomfortable problem. For a long time, kale has been at the top of the heath food list. But now there is concern that too much consumption of the leafy green could lead to potential kidney stones.
How is that possible?
Kale and many other foods contain high levels of oxalate. Oxalic acid is naturally occurring and found in plants such as spinach, chard, beets, berries and kale. When your urine contains higher levels of calcium and oxalate than it can dilute, those calcium and oxalate crystals bind together and form into hard masses, or “stones," in the kidney. The only way to remove them from the body is to “pass” the stones through urination.
For some people, the body will naturally expel oxalic acid without issue. However, other individuals might have a genetic predisposition that deters the body from processing the acid, resulting in kidney stones.
When should you avoid kale?
Kale is an excellent source of vitamin C and is packed with iron. It’s also a low-calorie food and is great for your skin due to its anti-aging properties. But with all things, moderation is a necessity. Fruit is beneficial for the body, but too much of it and you could deal with irritable bowel syndrome, frequent bloating or weight gain. The same goes for kale. Don’t get us wrong; you should still eat it, just don’t overdo it.
As mentioned earlier, if you have a predisposition to kidney stones you may want to decrease the amount of kale you’re consuming daily or opt for other foods with similar health benefits. Also, if you’ve had kidney stones in the past, speak to a physician about whether or not it’s wise to remove kale from your diet entirely.
Ways to avoid kidney stones
Now that you know kale isn’t necessarily the only culprit, how else can you avoid kidney stones? Besides reducing intake of high-oxalate foods, you can also counteract the formation of stones by:
- Hydrating often – Drinking more water helps prevents kidney stones because it ensures your urine output will be high. Not enough water means your body won’t have enough fluids to dissolve the oxalate crystals in your urine.
- Eating less salt – Too much salt in urine can prevent calcium from being reabsorbed into the blood. This causes high urine calcium levels, which can lead to stones.
- Cutting back on animal protein – Animal protein is often acidic and can increase uric acid, which can increase the likelihood of calcium oxalate kidney stones.
- Eating calcium-rich foods – Since kidney stones are formed by calcium and oxalates binding in the kidneys, it may seem counterintuitive to put more of that combination in your body. However, it is recommended that you eat calcium and high oxalate foods together, so they bind in your stomach and intestines – not your kidneys.
Are you a kale fanatic? If so, you may want to err on the safe side and reconsider how much kale or other oxalate-rich foods should be in your diet.
Find a doctor
If you have questions about your risk factors for kidney stones, contact the Primary Care Department at Swedish. We can accommodate both in-person and virtual visits.
Whether you require an in-person visit or want to consult a doctor virtually, you have options. Swedish Virtual Care connects you face-to-face with a nurse practitioner who can review your symptoms, provide instruction and follow up as needed. If you need to find a doctor, you can use our provider directory.
Join our Patient and Family Advisory Council.
This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.
