Are Oxalates Dangerous? Food List + Tips For Reducing Oxalate Content
Anyone with a history of kidney stones probably already knows about high-oxalate foods. These are foods that can contribute to kidney stone-causing crystals, affect your calcium absorption, and put you at risk for kidney disease down the line.
Consuming oxalates, also called oxalic acid, may not be dangerous for everyone else. This is one of those bio-individualized health questions that applies to people in specific circumstances but not to others. For my patients, optimizing nutrition means examining everything you eat to find any deficiencies or food triggers causing your symptoms.
If oxalates trigger health problems for you, you have several options.
I’ll try to simplify all of this so you can decide whether to ditch the oxalates, starting with what they do and where to find them.
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What Are Oxalates?
Oxalates are naturally occurring compounds that bind with calcium in plants. (1) For certain people, this process forms oxalate crystals that increase the risk for the formation of kidney stones as they build up.
They aren’t traditional antinutrients, as most people handle high-oxalate foods just fine. But for people at risk for kidney stones, they can interfere with the body’s ability to get the nutrients it needs for overall wellness.
To make matters more confusing, they’re typically in highly nutritious foods that do support wellness, like leafy greens, legumes, cereals, and nuts. It’s the oxalates themselves that aren’t essential to our health, and the build-up of oxalates can be harmful to some. (2)
Are Oxalates Bad For Me?
For most people, oxalates aren’t a big deal. Our bodies target them for excretion as they move through digestion without additional issues. If you’re at high risk for the types of kidney stones caused by oxalates, your oxalate consumption can be a problem.
For people with a history of or at risk for kidney stones, high oxalate intake may impact kidney function and contribute tokidney stones. Oxalates can bind with calcium in the urinary tract and cause kidney stones to form. These are called calcium oxalate kidney stones, the most common type of kidney stone.
Kidney stones can block the flow of urine and cause urinary tract infections. They can also increase the risk of chronic kidney disease, especially in those with primary hyperoxaluria. (3) Primary hyperoxaluria is the genetic form of a condition caused by too much oxalate in the urine.
You may not know if you have the risk factors for these stones until your healthcare provider does a series of tests after the fact. Unfortunately, it’s often the result of your first experience with kidney stones.
Since oxalates affect calcium absorption, especially in those with kidney disease, you could start noticing health issues associated with low calcium. These include:
- Muscle pain and fatigue
- Brittle nails and hair
- Numbness or tingling of the mouth, throat, feet, and/or hands
In severe cases, calcium deficiencies can affect bone health, leading to osteomalacia (soft bone disease) and osteoporosis. (4)
Too many oxalates can also mess with your gut. Kidney damage can increase inflammation along the digestive tract and wreak havoc on your microbiome and existing gut conditions. (5) A healthy microbiome is essential in excreting excess oxalates, so there are multiple implications here.
With my patients, I always start by trying to get to the root of any health problems. In most people, oxalates aren’t an issue. They may not even be the cause of your kidney dysfunction—you could be low in magnesium or dealing with adrenal fatigue. Maybe you need a natural detox or are not drinking enough water. (Yes, sometimes it is that simple.)
If you’re ready to get to the root of your issues, functional medicine can help. As one of the first functional medicine telehealth clinics in the world, we provide webcam health consultations and personalized medical advice for people around the globe.
The Top High-Oxalate Foods
Foods that contain over 10 mg of oxalates per serving are considered high-oxalate foods. Totals vary somewhat based on how foods are grown and tested, but we have a general idea of the biggest “offenders.”
Common high-oxalate foods include:
| Food | Oxalate Content (mg) |
| Spinach, raw | 656 |
| Rhubarb | 541 |
| Swiss chard | 350 |
| Rice bran | 281 |
| Buckwheat groats | 133 |
| Almonds | 122 |
| Corn grits | 97 |
| Skin-on baked potatoes | 97 |
| Navy beans | 76 |
| Beets | 76 |
| Cocoa powder | 67 |
| Cornmeal | 64 |
| Bran flakes | 57 |
| Okra | 57 |
| French fries | 51 |
| Cashews | 49 |
| Raspberries | 48 |
| Miso | 40 |
| Yams | 40 |
| Turnip | 30 |
| Rutabaga | 31 |
| Walnuts | 31 |
| Wheat flour | 29 |
| Sweet potatoes | 28 |
| Oranges | 29 |
| Peanuts | 27 |
| Dates/Dried figs | 24 |
| Avocados | 19 |
| All-purpose flour | 17 |
| Pumpkin seeds | 17 |
| Tomato sauce | 17 |
| Kiwi | 16 |
| Kidney beans | 15 |
| Parsnips | 15 |
| Tofu | 13 |
| Grapefruit | 12 |
| Sunflower seeds | 12 |
| Dried prunes | 11 |
| Collards | 10 |
Much of this list is full of high-fiber, phytonutrient-rich plant foods that you can eat as part of a healthy diet. A low-oxalate diet doesn’t have to be about completely eliminating these foods; it's really more about balance.
If you’re prone to kidney stones, first limit foods with very high levels of oxalates and watch your portion sizes of oxalate-rich foods. (6) You can also reduce the overall oxalate content in your food.
How To Reduce Oxalate Content
To reduce oxalate content in your food, you have a few options:
- Cooking: Steam, bake, or sauté leafy greens to reduce oxalate levels. Cooking can make it easier for your body to digest them, too. (Olive and coconut oils are low in oxalates.)
- Soaking: Soak beans, nuts, and seeds for 12 hours, drain them, then roast them at a low-to-medium temperature for 10-20 minutes to remove some of the oxalates.
- Moderating: Oxalate totals are based on serving sizes. Black pepper, a high-oxalate spice, usually comes in a dash. Its effects are negligible compared to those of a serving of greens.
- Pair with calcium: Some foods with high amounts of oxalates are high in calcium, but pairing them with low-fat dairy, eggs, or seafood can boost your calcium intake.
- Watch your vitamin C: Vitamin C is essential to immune system health but can also be metabolized into oxalate. (7) Many citrus fruits are higher oxalate foods, as well. If you’re at risk or concerned about kidney stones, it might be a good idea to get your vitamin C from food but not take an additional vitamin C supplement to keep your intake moderate.
- Choose low-oxalate alternatives: If you’re at an increased risk of kidney stones and watching your intake of oxalates, you have lots of options for low-oxalate foods.
Choose blueberries, blackberries, or strawberries over raspberries and nectarines over oranges. Go for kale, broccoli, and Brussels sprouts over spinach and lentils over navy beans. Dried cranberry is a good choice over dates and figs.
Salmon and sardines are good animal proteins that can help make sure you’re getting enough calcium. Supplements can help here, too.
Dairy is generally low-oxalate, but soy milk is a good alternative if you can’t have it due to food intolerances. (Soybeans are a moderate source of oxalates at 7 mg/serving.)
If you’re at high risk for kidney stones, drink plenty of water and eat lots of hydrating foods. Water helps your body reduce waste through urine and dilute high concentrations of oxalates. (8) High-sugar and high-sodium foods can have the opposite effect.
FAQs
For most people at risk, high oxalate level symptoms are the formation of kidney stones. Kidney stones cause severe pain in the side or back, lower abdomen, or groin, pain during urination, blood in your urine, and frequent urination.
In those with IBD-induced kidney dysfunction or imbalanced gut microbiomes, high oxalate levels can exacerbate symptoms like abdominal pain, bloating, and diarrhea. (9)
Many high-oxalate foods, such as leafy greens and legumes, are rich sources of fiber, antioxidants, and essential vitamins and minerals like potassium, iron, and magnesium. The benefits of high-oxalate foods may outweigh the risks for most healthy adults without a history of kidney issues.
Drinking plenty of water, especially after sweating and heavy exercise, can help your body excrete oxalates more efficiently. Avoid too much sugar and sodium and prioritize calcium-rich foods to avoid calcium deficiencies, which are more common in those affected by oxalates.
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- Franceschi, V.R. & Nakata, P.A. (2005). Calcium oxalate in plants: formation and function. Annual Review of Plant Biology, 56, 41-71.
- Bargagli, M., Tio, M.C., Waikar, S.S., et al. (2020). Oxalate intake and kidney outcomes. Nutrients, 12(9), 2673.
- Rule, A.D., Bergstralh, E.J., Melton, L.J. 3rd, et al. (2009). Kidney stones and the risk for chronic kidney disease. Clinical Journal of the American Society of Nephrology, 4(4), 804-811.
- Cashman, K.D. (2002). Calcium intake, calcium bioavailability and bone health. British Journal of Nutrition, 87 Suppl 2, S169-S177.
- Mahmoodpoor, F., Rahbar Saadat, Y., Barzegari, A., et al. (2017). The impact of gut microbiota on kidney function and pathogenesis. Biomedecine & Pharmacotherapy, 93, 412-419.
- Crivelli, J.J., Wood, K.D., & Assimos, D.G. (2021). Is it time to retire the low-oxalate diet? No! Journal of Endourology, 35(10), 1435-1437.
- Lamarche, J., Nair, R., Peguero, A., et al. (2011). Vitamin C-induced oxalate nephropathy. International Journal of Nephrology, 146927.
- Mitchell, T., Kumar, P., Reddy, T, et al. (2019). Dietary oxalate and kidney stone formation. American Journal of Physiology-Renal Physiology, 316(3), F409-F413.
- Liu, M., Devlin, J.C., Hu, J., et al. (2021). Microbial genetic and transcriptional contributions to oxalate degradation by the gut microbiota in health and disease. Elife, 10, e63642.
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BY DR. WILL COLE
Dr. Will Cole, DNM, IFMCP, DC is a leading functional medicine expert who consults people around the globe, starting one of the first functional medicine telehealth centers in the world. Named one of the top 50 functional and integrative doctors in the nation, Dr. Will Cole provides a functional medicine approach for thyroid issues, autoimmune conditions, hormonal imbalances, digestive disorders, and brain problems. He is also the host of the popular The Art of Being Well podcast and the New York Times bestselling author of Intuitive Fasting, Ketotarian, Gut Feelings, and The Inflammation Spectrum.
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