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Oxalates are natural compounds found in many plant foods, with spinach, rhubarb, Swiss chard, beets, almonds and other nuts, potatoes, wheat bran, chocolate and tea among the richest common sources. For most people they are not a problem: the body handles them and gets rid of them in urine and stool. They matter mainly for people who form calcium oxalate kidney stones, the most common kind of stone, and even then kidney groups say the first steps are enough fluid and enough calcium, not cutting out every plant food. Below is what oxalates are, which foods are high and low, and when to talk to a clinician.
Peptide Labs does not sell oxalate tests or low-oxalate products. This article is general nutrition information, not medical advice. If you have had a kidney stone, follow the plan from your own clinician or dietitian.
Key Takeaways
- Oxalate is a plant compound; about half of the oxalate in urine comes from food and half is made by the body.
- Spinach, chard, rhubarb, beets, nuts, potatoes with skin, bran, chocolate and tea are common high sources.
- Dairy, meat, fish and eggs contain essentially no oxalate.
- Eating calcium-rich food at meals lowers how much oxalate is absorbed.
- The National Kidney Foundation says a strict low oxalate diet is not helpful for most people.
What are oxalates?
Oxalate (oxalic acid and its salts) is made by many plants and is also an end product of human metabolism. A 2019 review by kidney stone researchers at Wake Forest (Mitchell and colleagues, American Journal of Physiology) notes that in healthy people roughly half of the oxalate in urine comes from the diet and half is made inside the body. In the gut, much of the oxalate in food is already bound to calcium as insoluble crystals that pass out in stool; only the dissolved part can be absorbed. Absorption studies in that review found people absorb a small share of soluble oxalate, with large differences from person to person.
Oxalate also binds calcium inside foods. The NIH Office of Dietary Supplements (ODS) explains that only about 5% of the calcium in spinach is absorbed, compared with about 27% from milk, because of oxalic acid. ODS adds that in a varied diet these effects probably have little or no nutritional consequence, so there is no reason to fear spinach; just do not count it as a main calcium source. Our calcium foods guide covers better-absorbed options.
High oxalate foods
There is no USDA oxalate field, and published oxalate numbers vary with the lab method, plant variety, growing conditions and cooking, a problem researchers Holmes and Kennedy highlighted when they developed better methods in 2000. So instead of precise numbers, the table groups foods by what kidney organizations and the research review name. Your dietitian may use a specific database with serving values if you need a detailed plan.
| Food | Where it is named as high | Notes |
|---|---|---|
| Spinach | NIDDK, NKF, Mitchell 2019 review (avoid group) | Among the richest common sources |
| Swiss chard | NKF, Mitchell 2019 review (avoid group) | Leafy green |
| Rhubarb | NIDDK, NKF, Mitchell 2019 review (avoid group) | Stalks are very high |
| Star fruit | Mitchell 2019 review (avoid group) | Listed in the avoid group |
| Beets | NKF, Mitchell 2019 review (limit group) | Both roots and greens |
| Almonds and other nuts | NIDDK, NKF, Mitchell 2019 review (limit group) | Peanuts too, per NIDDK |
| Potatoes with skin | NKF, Mitchell 2019 review (limit group) | Skin adds oxalate |
| Wheat bran and bran cereals | NIDDK, Mitchell 2019 review (limit group) | Rice bran is also high |
| Chocolate and cocoa | Mitchell 2019 review (limit group) | Hot chocolate counts |
| Brewed tea | Noonan 1999 review, UChicago program | Major source in tea-drinking diets |
| Navy beans, sweet potatoes, collard greens | NKF, NIH ODS | Other foods often named |
Several of these are otherwise nutritious foods covered in our guides to almonds, beetroot and sweet potatoes. Being on this list does not make a food unhealthy; it only matters for people a clinician has told to watch oxalate.
Supplements and drinks to know about
Concentrated plant products can carry more oxalate than a normal serving of food. The National Kidney Foundation names turmeric, cinnamon and green superfood blends. In a small 2008 crossover study of 11 healthy adults (Tang and colleagues, American Journal of Clinical Nutrition), turmeric raised urine oxalate more than cinnamon, because most of turmeric’s oxalate dissolves in water. Case reports have also linked heavy daily chaga mushroom powder to oxalate kidney injury, as covered in our mushroom coffee guide. See our turmeric side effects and cinnamon articles before using either in supplement form, and ask about juice cleanses built on spinach or beets if you have stone history. Our vitamin C guide discusses the separate question of high-strength vitamin C supplements and stones.
Low oxalate foods
The University of Chicago Kidney Stone Program, which bases its lists on the Harvard School of Public Health oxalate database, gives these as lower-oxalate examples. They show that a low oxalate diet can still include plenty of plants:
- Vegetables: kale, lettuce, cauliflower, cucumber and mushrooms.
- Fruits: bananas and blueberries.
- Grains: white rice.
- Animal foods: milk, yogurt, cheese, meat, fish and eggs contain essentially no oxalate.
- Drinks: water and coffee.
Values differ between databases, so if you are on a prescribed plan, use the list your dietitian gives you rather than mixing lists from the internet.
Calcium, fluids and oxalate: why the meal matters
The most useful fact about oxalates is that calcium in the same meal binds oxalate in the gut so less is absorbed. The National Kidney Foundation says eating enough calcium can help with calcium oxalate stones, and NIDDK says calcium in the right amounts can block other substances in the digestive tract that may cause stones. That is why cutting calcium is usually the wrong move for stone formers. NIDDK suggests calcium from low-oxalate plant foods as well as dairy. The USDA table below shows common calcium foods per serving with the FDA Daily Value.
| Food (USDA FDC ID) | Serving | Calcium | % Daily Value |
|---|---|---|---|
| Plain low-fat yogurt (170886) | 6 oz (170 g) | 311 milligrams | 24% |
| Milk, 2% (171267) | 1 cup (244 g) | 293 milligrams | 23% |
| Orange juice with added calcium (169920) | 1 cup (249 g) | 349 milligrams | 27% |
| Kale, cooked (169238) | 1 cup (118 g) | 177 milligrams | 14% |
| Bok choy, cooked (170391) | 1 cup (170 g) | 158 milligrams | 12% |
| Spinach, cooked (168463) | 1 cup (180 g) | 245 milligrams | 19%, but poorly absorbed |
NIDDK calls drinking enough liquid, mainly water, the most important thing you can do to lower stone risk, and it notes that high sodium and large amounts of animal protein can raise risk. Soaking and boiling also lower the oxalate in vegetables, because oxalate leaches into the cooking water, according to a 1999 review by Noonan and Savage. Questions about calcium pills belong with your clinician; our calcium supplement guide explains the label differences.
Who actually needs a low oxalate diet?
Not everyone, and not even every stone former. The National Kidney Foundation states that a strict low oxalate diet is not helpful for most people because it makes a balanced diet hard. The University of Chicago program says it is mainly for people whose stones contain calcium oxalate and whose 24-hour urine test shows high oxalate. Your clinician decides that from a stone analysis and urine testing, and some people are also prescribed medicines such as potassium citrate (see our potassium citrate guide). Medicines matter too: the alli label (orlistat, a drug we cover in our alli guide) says to ask a doctor before use if you have ever had kidney disease or kidney stones.
Online claims that oxalates cause widespread pain, fatigue or skin problems, or that people go through oxalate dumping when they cut back, come mainly from anecdotes; we found no controlled trials supporting them. Seek care promptly for severe side or back pain, blood in urine, fever with urinary symptoms or trouble passing urine. Our sibling guide to nightshade vegetables looks at another food group with a loud online reputation.
Frequently Asked Questions
What are oxalates?
Natural compounds made by many plants and by the body. They bind calcium and leave through urine and stool.
What are the main high oxalate foods?
Spinach, Swiss chard, rhubarb, star fruit, beets, almonds and other nuts, potatoes with skin, wheat bran, chocolate and brewed tea are commonly named by kidney groups and researchers.
What are some low oxalate foods?
Dairy, meat, fish and eggs have essentially none, and kale, lettuce, cauliflower, cucumber, mushrooms, bananas, blueberries and white rice are lower-oxalate examples in the Harvard-based lists.
Should I follow a low oxalate diet?
Only if your clinician recommends it, usually after a stone analysis and urine test. The National Kidney Foundation says a strict version is not helpful for most people.
Does calcium help with oxalates?
Yes. Calcium eaten in the same meal binds oxalate in the gut, so less is absorbed. Kidney groups advise against cutting calcium.
Does cooking reduce oxalates?
Boiling and soaking lower oxalate because some leaches into the water, which is then discarded.
Questions about a label? Contact us or read our Buyer’s Guide. Food comes first; follow the label and ask a healthcare provider before starting a supplement or changing your diet for a medical reason, especially if you take medicines, are pregnant or have kidney disease. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Last reviewed October 2026.
Related guides: Nightshade Vegetables: List, Nutrition and Are Nightshades Bad for You?, Foods High in Calcium: USDA List, Non-Dairy Sources and Absorption, Leafy Greens: USDA List of Dark Greens, Spinach vs Kale and Tips.