Is spinach bad for you?
The claim: Spinach is bad for you because of oxalate.
Last checked 9 October 2026
Not for most people. Spinach is one of the highest-oxalate foods there is, and that matters if you form calcium oxalate kidney stones, or have hyperoxaluria or a gut condition that raises oxalate absorption. For everyone else, a large US study concluded dietary oxalate is not a major risk factor, and spinach's calcium is the real casualty: far less of it is absorbed than from milk.
Oxalate is a plant compound that binds calcium. The US kidney institute, NIDDK, lists spinach among the foods people who have had calcium oxalate stones may want to avoid, and says drinking enough water matters most. In three large US cohorts, people who ate spinach often had somewhat more stones in two of the three groups, but the authors concluded dietary oxalate is not a major risk factor. Boiling spinach and pouring away the water removes much of the soluble oxalate. Heavy daily juicing, with dehydration, has caused kidney failure, rarely.
What oxalate is, and where it is
A 2023 review of oxalate in foods sums it up:
Oxalate is an antinutrient present in a wide range of foods, with plant products, especially green leafy vegetables, being the main sources of dietary oxalates.
The results showed that spinach, New Zealand spinach, rhubarb, Swiss chard, taro leaves, sorrel, soybean, amaranth, parsley, and licorice contained high oxalate levels and can be considered high-oxalate foods, especially some green leafy vegetables.
And at the other end:
In contrast, others can be referred to as low-oxalate foods: fruits (except for star fruit, elderberry, and dried fig), cabbage, broccoli, cauliflower, cucumber, kale, pumpkin, chickpeas, lentils, cowpea, arugula, cress, garlic, and green onion.
Kale, broccoli and cauliflower are on the low list, so not all greens are the same.
How much is in a cup
Here is the oxalate in a cup of each raw high-oxalate vegetable this site has a figure for. Spinach has a range, because published measurements differ widely:
published oxalate values are 329.6–2350 mg total oxalates/100 g fresh weight (FW) for spinach
Many factors can influence oxalate accumulation in plants, such as growth, ripeness, variety, season, time of harvest, and cultivation conditions (e.g., use of nitrate fertilizer or soil conditions)
| Food | Oxalate per 100 g, raw | Cup | Oxalate in that cup | Source |
|---|---|---|---|---|
| Rhubarb | 986.7 mg (raw stalks) | 1 cup, diced (122 g) | 1,200 mg | Savage GP, Vanhanen L, Mason SM, Ross AB 2000, J Food Compos Anal 13:201-206 (doi:10.1006/jfca.2000.0879), Table 2 (mg/100 g wet matter) |
| Spinach | 329.6–2,350 mg (raw) | 1 cup (30 g) | 98.9–705 mg | Salgado et al. 2023, Foods 12(17):3201 (review of published values) |
| Swiss chard | 525.5 mg (raw leaves) | 1 cup (36 g) | 189 mg | Savage GP, Vanhanen L, Mason SM, Ross AB 2000, J Food Compos Anal 13:201-206 (doi:10.1006/jfca.2000.0879), Table 2 (mg/100 g wet matter) |
| Beets (beetroot) | 105 mg (raw beetroot, before blanching) | 1 cup (136 g) | 143 mg | Lisiewska et al. 2011, Agricultural and Food Science 20:305–314 |
These are raw figures. Boiling and pouring away the water lowers the soluble part (see "Does cooking help?" below).
Kidney stones: what the evidence says
A large US study followed three groups of health professionals for years. Spinach was the main source of oxalate in their diets:
Spinach accounted for >40% of oxalate intake.
The relative risks for participants who ate eight or more servings of spinach per month compared with fewer than 1 serving per month were 1.30 (95% CI 1.08 to 1.58) for men and 1.34 (95% CI 1.10 to 1.64) for older women.
Oxalate intake and spinach were not associated with risk in younger women. These data do not implicate dietary oxalate as a major risk factor for nephrolithiasis.
The US kidney institute's advice is aimed at people who have already had stones:
Drinking enough liquid, mainly water, is the most important thing you can do to prevent kidney stones.
If you’ve had calcium oxalate stones, you may want to avoid these foods to help reduce the amount of oxalate in your urine:
Even though calcium sounds like it would be the cause of calcium stones, it’s not. In the right amounts, calcium can block other substances in the digestive tract that may cause stones.
Its list of foods to consider avoiding is nuts, peanuts, rhubarb, spinach and wheat bran.
Low-oxalate diets
Low-oxalate diets are for people with specific conditions. A patient charity's guide:
The general daily target is under 100 mg of oxalate per day (some clinicians recommend under 50 mg)
This guide is especially relevant for people with hyperoxaluria, recurrent calcium oxalate kidney stones, or related GI conditions
Pairing calcium-rich foods with meals – not supplements between meals – is equally important
That is advice for patients, not a safety limit for everyone: no food safety body we found has set one for oxalate.
Spinach's calcium
Spinach looks like a good source of calcium on a label. A study in healthy adults measured how much of it the body takes up, against milk:
Absorption was higher from milk in every case, with the mean absorption from milk averaging 27.6% and from spinach, 5.1%.
These results conclusively establish that spinach Ca is much less readily available than milk Ca.
Measurement of both Ca and oxalate in our test spinach revealed a very slight stoichiometric excess of oxalate; hence it is likely that all of the spinach Ca was effectively bound.
So far less of spinach's calcium is absorbed than milk's, because the oxalate binds it.
Does cooking help?
Boiling does, if you pour the water away:
Boiling markedly reduced soluble oxalate content by 30-87% and was more effective than steaming (5-53%) and baking (used only for potatoes, no oxalate loss).
Because soluble sources of oxalate appear to be better absorbed than insoluble sources, employing cooking methods that significantly reduce soluble oxalate may be an effective strategy for decreasing oxaluria in individuals predisposed to the development of kidney stones.
The figures in the table above are for raw vegetables.
When it does go wrong
Very large amounts can harm the kidneys. Doctors who reported one case wrote:
Acute oxalate nephropathy (AON) induced by high dietary intake of oxalate-rich food is a rare cause of acute kidney injury and end-stage renal disease (ESRD).
Six months earlier, he started a daily oxalate-rich fruit and vegetable juice diet high in spinach, with a calculated daily oxalate dietary intake of 1500 mg, about 10 times a typical diet.
A year later, he remains dialysis dependent.
That was a daily juice habit, with dehydration, not a side of spinach with dinner, and the same report calls it rare.
What you'll hear at the table
Spinach comes up whenever plants and "antinutrients" are argued over. Here is each claim, checked against its source.
You'll hear: Spinach is one of the highest-oxalate foods.
Holds up
The results showed that spinach, New Zealand spinach, rhubarb, Swiss chard, taro leaves, sorrel, soybean, amaranth, parsley, and licorice contained high oxalate levels and can be considered high-oxalate foods, especially some green leafy vegetables.
You'll hear: Oxalate gives you kidney stones.
Partly holds up
For people who form calcium oxalate stones, cutting oxalate is standard advice. For everyone else, a large US study found eating spinach often went with somewhat more stones in two of its three groups, and still concluded:
Oxalate intake and spinach were not associated with risk in younger women. These data do not implicate dietary oxalate as a major risk factor for nephrolithiasis.
You'll hear: Spinach is a great source of calcium.
Doesn't hold up
On a label, maybe. In the body, little of it is absorbed:
Absorption was higher from milk in every case, with the mean absorption from milk averaging 27.6% and from spinach, 5.1%.
You'll hear: Boiling spinach gets rid of the oxalate.
Partly holds up
Much of the soluble part, if you pour the water away. Not all of it:
Boiling markedly reduced soluble oxalate content by 30-87% and was more effective than steaming (5-53%) and baking (used only for potatoes, no oxalate loss).
You'll hear: Green smoothies can wreck your kidneys.
Partly holds up
Heavy daily juicing has, rarely, together with dehydration:
Six months earlier, he started a daily oxalate-rich fruit and vegetable juice diet high in spinach, with a calculated daily oxalate dietary intake of 1500 mg, about 10 times a typical diet.
Acute oxalate nephropathy (AON) induced by high dietary intake of oxalate-rich food is a rare cause of acute kidney injury and end-stage renal disease (ESRD).
You'll hear: Eat calcium with your spinach and it helps.
Holds up
That is the advice for people on low-oxalate diets, and the US kidney institute says calcium can block what causes stones:
Pairing calcium-rich foods with meals – not supplements between meals – is equally important
Even though calcium sounds like it would be the cause of calcium stones, it’s not. In the right amounts, calcium can block other substances in the digestive tract that may cause stones.
You'll hear: Meat is safer than spinach for kidney stones.
Doesn't hold up
For people who have had stones, the US advice points the other way:
Eating animal protein may increase your chances of developing kidney stones.
Consider replacing some of the meat and animal protein you would typically eat with beans, dried peas, and lentils, which are plant-based foods that are high in protein and low in oxalate.
You'll hear: Everyone should go low-oxalate.
Doesn't hold up
Low-oxalate diets are written for people with specific conditions:
This guide is especially relevant for people with hyperoxaluria, recurrent calcium oxalate kidney stones, or related GI conditions
Despite a clear relationship between dietary oxalate, calcium oxalate, and kidney stone risk, the connection might be more complex than previously thought due to the impact of cooking techniques, calcium intake, endogenously produced oxalate, and gastrointestinal health. Foods which contain oxalates, such as fruits and vegetables, have a wide range of beneficial compounds that might outweigh possible negative implications on human health.
You'll hear: Drinking water matters more than cutting spinach.
Holds up
Drinking enough liquid, mainly water, is the most important thing you can do to prevent kidney stones.
The referee's verdict
- Right, for the worried side: spinach is one of the highest-oxalate foods; people who form calcium oxalate stones are advised to limit it; far less of its calcium is absorbed than milk's; and very large daily amounts, such as heavy juicing with dehydration, have caused kidney failure in rare cases.
- Right, for the "eat your greens" side: a large US study did not find dietary oxalate to be a major risk factor for stones; boiling removes much of the soluble oxalate; many greens, including kale and broccoli, are low in oxalate; and for people who have had stones, the US kidney institute puts water first and animal protein on its list of things to watch.
- Not settled: how much the oxalate in ordinary amounts of spinach matters for people who don't form stones.
Try it with your own plate
Put spinach on the plate builder to see its oxalate beside everything else on your plate.
Sources
- Salgado N, Silva MA, Figueira ME, Costa HS (2023). Oxalate in Foods: Extraction Conditions, Analytical Methods, Occurrence, and Health Implications. Foods 12(17): 3201. doi:10.3390/foods12173201Evidence: Not applicable. A review of published measurements.Read: PMC full text, in Chrome
- Oxalosis & Hyperoxaluria Foundation. Low-Oxalate Diet: The Complete Guide With Food Lists.Evidence: Not applicable. A patient charity's diet guide.Read: page text, in Chrome
- Taylor EN, Curhan GC (2007). Oxalate intake and the risk for nephrolithiasis. Journal of the American Society of Nephrology 18(7): 2198–2204. doi:10.1681/ASN.2007020219Evidence: Human observational studyRead: PubMed abstract, in Chrome
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Eating, Diet, & Nutrition for Kidney Stones (last reviewed May 2017).Evidence: Regulatory assessment. US government health advice.Read: page text, in Chrome
- Heaney RP, Weaver CM, Recker RR (1988). Calcium absorbability from spinach. American Journal of Clinical Nutrition 47(4): 707–709. doi:10.1093/ajcn/47.4.707Evidence: Human trial. A randomized crossover study in 13 healthy adults.Read: PubMed abstract, in Chrome
- Chai W, Liebman M (2005). Effect of different cooking methods on vegetable oxalate content. Journal of Agricultural and Food Chemistry 53(8): 3027–3030. doi:10.1021/jf048128dEvidence: Measured in foodRead: PubMed abstract, in Chrome
- Chaudhari H, Michaud J, Srialluri N, Mahendrakar S, Granz C, Yudd M (2022). Acute Oxalate Nephropathy Caused by Excessive Vegetable Juicing and Concomitant Volume Depletion. Case Reports in Nephrology 2022: 4349673. doi:10.1155/2022/4349673Evidence: Case reportRead: PMC full text, in Chrome