Oxalates are natural compounds found in many plant-based foods, and for most people they pass through the body without issue. However, for the estimated one in ten adults who develop kidney stones — most of which are calcium oxalate stones — understanding which foods are high in oxalates can be genuinely important. Knowing where oxalates hide helps you make smarter choices without giving up nutritious eating.
1. Spinach
Spinach is often considered a superfood, but it tops the list of oxalate foods by a wide margin. A single cooked cup can contain over 750 milligrams of oxalate. Research indicates that among common high-oxalate foods, only spinach significantly increased urinary oxalate excretion by about 29.3 milligrams, while other foods had minimal impact. This does not mean you need to eliminate spinach entirely. However, if you are prone to kidney stones, limiting portion sizes or pairing spinach with calcium-rich foods may help reduce oxalate absorption. Cooking spinach and discarding the water can also lower its oxalate content somewhat.
2. Almonds
Almonds are packed with healthy fats, protein, and vitamin E, yet they also rank among the higher oxalate foods in the nut family. A quarter cup of almonds contains roughly 120 to 150 milligrams of oxalate. Studies suggest that the bioavailability of oxalate from almonds sits around 2.8 percent, meaning your body absorbs a relatively small fraction. Still, frequent snacking on large quantities could add up over time. Enjoying almonds in moderation and staying well-hydrated is a practical approach for most people.
3. Beets
Beets are celebrated for their deep color, natural nitrates, and potential cardiovascular benefits. They are also one of the more concentrated sources of dietary oxalate. Both raw and cooked beets can deliver over 100 milligrams per serving. The oxalate is present in both the root and the greens, with beet greens actually containing even higher levels. If you enjoy beets regularly, consider balancing them with lower-oxalate vegetables throughout your day. Roasting or boiling beets and draining the liquid may slightly reduce the total oxalate you consume.
4. Sweet Potatoes
Sweet potatoes offer fiber, beta-carotene, and a satisfying natural sweetness that makes them a kitchen staple. However, a medium baked sweet potato can contain anywhere from 60 to over 140 milligrams of oxalate depending on the variety. This places them firmly in the moderate-to-high category among oxalate foods. Peeling sweet potatoes before cooking may help, since some oxalate concentrates near the skin. Rotating sweet potatoes with lower-oxalate alternatives like regular potatoes or butternut squash is a simple way to keep your overall intake in check.
5. Rhubarb
Rhubarb is a tart, seasonal ingredient popular in pies and jams, but it is one of the highest oxalate foods available. A half-cup of cooked rhubarb can contain over 500 milligrams of oxalate. The oxalic acid in rhubarb is part of the reason the leaves are considered toxic and only the stalks are eaten. Because of its extreme oxalate density, clinical guidance often recommends that people with a history of calcium oxalate kidney stones avoid rhubarb altogether. For everyone else, enjoying it occasionally in small portions is unlikely to cause problems.
6. Dark Chocolate and Cocoa
Dark chocolate has earned a reputation as a heart-friendly indulgence, rich in antioxidants and minerals. Yet cocoa beans are naturally high in oxalate, and a one-ounce serving of dark chocolate may contain 20 to 30 milligrams. The good news is that research suggests the bioavailability of oxalate from chocolate is relatively low compared to leafy greens. This means your body absorbs less of it into the bloodstream. Moderate chocolate consumption is unlikely to significantly raise urinary oxalate for most individuals. Sticking to reasonable portions remains the best strategy.
7. Peanuts
Peanuts and peanut butter are affordable protein sources enjoyed worldwide, but they carry a notable oxalate load. A quarter cup of peanuts provides roughly 25 to 30 milligrams of oxalate. Clinical evidence shows that oxalate absorption from nuts and legumes ranges from about 2 to 15 percent, influenced by the soluble form and what else you eat alongside them. Pairing peanut butter with calcium-containing foods like yogurt or milk may help bind some oxalate in the gut before it is absorbed. This small dietary tweak can make a meaningful difference over time.
8. Brewed Tea
Tea is one of the most consumed beverages in the world, and both black and green varieties contain measurable oxalate. A standard cup of black tea can contain between 12 and 30 milligrams depending on brewing time and tea variety. However, studies indicate the bioavailability of oxalate from brewed tea is remarkably low, estimated at only about 0.08 percent. This suggests that for most tea drinkers, the oxalate contribution is minimal in practical terms. If you drink several cups daily and have oxalate concerns, consider shortening brew times or alternating with herbal teas that tend to be lower in oxalate.
9. Swiss Chard
Swiss chard is a colorful leafy green loaded with vitamins A, C, and K, along with magnesium and iron. It is also one of the higher oxalate foods in the vegetable world. One cooked cup can deliver over 600 milligrams of oxalate. Research highlights that green leafy vegetables are primary sources of dietary oxalate, and controlled intake is especially important for those managing kidney stone risk. Boiling Swiss chard rather than sautéing it can leach a portion of the oxalate into the cooking water. If you love leafy greens, rotating chard with lower-oxalate options like kale or romaine lettuce is a smart move.
10. Soy Products
Soy-based foods like tofu, edamame, and soy milk are protein-rich staples in plant-based diets, yet they contain moderate to high levels of oxalate. A cup of soy milk may have 20 to 30 milligrams, while textured soy protein can contain even more. The oxalate content also varies significantly by brand and processing method. Fermented soy products such as tempeh and miso tend to have somewhat lower oxalate levels than unfermented varieties. If soy is a regular part of your diet, choosing fermented options and drinking plenty of water throughout the day are practical ways to manage your overall oxalate exposure.
Understanding which foods are high in oxalates does not mean you need to eliminate them from your diet entirely — most people tolerate these foods without any issues. The key is awareness, moderation, and pairing high-oxalate foods with calcium-rich options to reduce absorption. Talk to your doctor or a registered dietitian if you have a history of kidney stones or other concerns about your oxalate intake.
Medical Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional before making health decisions.
