Kidney stones are crystal-type masses that develop inside the kidneys (1). Kidney stones form for a variety of reasons, but food with high oxalates can be one potential contributor. Although these foods are healthy foods, their high oxalate content can be problematic to those who get frequent or recurring kidney stones (2).
There are four main types of kidney stones including calcium oxalate, uric acid, struvite, and cysteine (1), (3) (4). Calcium oxalate, which is the most common type, develop from inadequate fluid and calcium intake as well as other conditions. Uric acid kidney stones usually develop from genetic factors and animal protein foods (5). Struvite kidney stones occur from urinary tract infections (6). Overall, kidney stones form by high levels of calcium, phosphorus, and oxalate in the urine (1). Problems only arise when the levels of these reach high amounts, as they are normally present in healthy urine.
Symptoms of kidney stones include severe pain in the lower back, stomach pain or ache, nausea, vomiting, blood in the urine, discolored urine, fever, and chills (7), (8). In many cases, kidney stones can pass on their own, although they are usually very painful. If there are severe complications, some kidney stones may need surgery or other procedures to minimize the risk of further infection (9), (10).
Make sure to drink plenty of fluid if you suspect you may have kidney stones, and contact your doctor right away if you have severe pain (11). Kidney stones can increase the risk of getting chronic kidney disease (7). You can avoid kidney stones by watching your diet. Be sure you do not have too much salt and maintain a healthy diet (12).
Summary: Kidney stones are crystal-like formations that are often caused by high oxalate foods and many other reasons. Calcium oxalate, uric acid, struvite, and cysteine are four types of kidney stones. Symptoms include lower back or stomach pain, nausea, vomiting, bloody or discolored urine, fever, and chills. If you experience kidney stones, watching your diet and drinking fluid will help reduce recurrent risk.
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Foods that cause kidney stones
To avoid the most common type of kidney stone, calcium oxalate, it is important to drink plenty of water daily, maintain a healthy weight, and avoid excessive amounts of certain foods high in oxalates (13). Just because these foods can cause kidney stones does not mean you cannot eat them. If you have no history or family history of kidney stones, incorporating these foods can be beneficial to your overall health and wellbeing.
Here are foods that are high in oxalates and can contribute to kidney stones:
Spinach is one of the most problematic foods for those who suffer from kidney stones. Spinach is extremely high in oxalates. Just one cup of spinach contains 656 mg of oxalates. Cooked and raw spinach both have high oxalates, but cooked spinach contains even more at 755 mg (14), (15). Although spinach is a nutrient-rich food high in vitamin A and vitamin C, it is better to avoid this food if you have kidney stones. Not to worry, there are many vegetables to include in your diet instead. Vegetables low in oxalates include asparagus, Brussel sprouts, cauliflower, kale, endive, iceberg lettuce, artichokes, cucumbers, peas, zucchini, parsnips, tomatoes, carrots, celery, green beans, mushrooms, onions, and peppers (16).
Summary: One cup of spinach contains 656 mg of oxalates. Cooked spinach contains 755 mg. Spinach is a nutrient-rich food, but for those who often experience kidney stones, spinach should be limited in the diet. Instead, consume asparagus, brussels sprouts, cauliflower, kale, endive, iceberg lettuce, artichokes, cucumbers, peas, zucchini, parsnips, and much more instead.
2. Almonds and Cashews
Although almonds and cashews are a healthy addition to most diets, they are both high in oxalates. Skip these types of nuts if you suffer from recurring kidney stones or you think you might have kidney stones. One ounce of almonds contains 122 mg of oxalates (17). Other nuts that are nutritious but contain a lot of oxalates are pistachios, peanuts, walnuts, pine nuts, and brazil nuts (18).
Almonds and cashews include high levels of intestinal soluble oxalate, making them a bad choice for those with kidney disease or kidney stones. If you have calcium oxalate kidney stones or uric acid kidney stones, your doctor may tell you to avoid these altogether or limit your intake.
Summary: If you suffer from recurrent kidney stones, reduce your intake of almonds and cashews, which are high in oxalates. One ounce of almonds has 122 mg. Pistachios, peanuts, walnuts, pine nuts, and brazil nuts also contain oxalates. If you suffer from calcium oxalate or uric acid kidney stones, you may focus on avoiding these altogether or limiting your intake.
3. Miso Soup
Just one cup of miso soup contains 111 mg of oxalates. Miso soup is a staple dish in Asian cultures that typically contains small pieces of tofu and seaweed. This soup is particularly high in oxalates, making it food to avoid for those with kidney issues (19). If you feel like you have kidney stones, avoid this soup.
Summary: One cup of miso soup has 111 mg of oxalates. Avoid or consume less of this soup if you experience kidney stones.
4. Animal Protein
Animal protein is not high in oxalates, but too much of it can contribute to uric acid kidney stones (12). This includes all types of animal protein like chicken, turkey, eggs, seafood, and red meat. A small amount of animal protein will not cause kidney stones. However, larger servings built up over time creates too much uric acid in the body, which can lead to painful kidney stones (16).
Try to stick to the portion size rule, where your animal protein size is not larger than the palm of your hand. That normally amounts to about 4 to 6 ounces, making it a safe size to enjoy your protein without the risk of kidney stones.
Summary: Animal protein does not have high oxalate content, but does contribute to uric acid kidney stones. All protein sources such as chicken, turkey, eggs, seafood, and red meat fit into this category. Consume smaller amounts of animal protein to prevent uric acid kidney stones. A 4-ounce portion, or the size of your palm, is the proper serving size of animal protein.
Okra is a highly nutritious food that contains vitamin K, protein, healthy fats, potassium, fiber, and more (20). However, okra is another vegetable extremely high in oxalates (12). Get your vitamins and minerals from other vegetables low in oxalates if you have or get frequent kidney stones.
Summary: Okra is very nutritious containing vitamin K, protein, healthy fats, potassium, and fiber. However, it does have high oxalates, so focus on eating vegetables low in oxalate if you suffer from kidney stones.
Rhubarb is another vegetable rich in oxalates, so it’s best to avoid it if you’re prone to kidney stones (12). It has 541 mg of oxalates in just ½ cup. Rhubarb is a leafy green vegetable with long red stalks. It has a similar texture to celery with a sour taste. It is often included in desserts because it has a sweet taste when cooked.
Summary: Rhubarb contains 541 mg of oxalates in 1/2 cup serving. If you suffer from kidney stones, reduce intake of rhubarb in all forms including rhubarb pie or other baked goods.
7. Cocoa Powder
Cocoa powder is another food to avoid is you have or are prone to kidney stones (21). Raw cocoa powder has 624 mg of oxalates in 100 grams. Cocoa powder and dark chocolate are usually often a health food because of their high nutritional content (22). But it should be left behind for those with kidney problems.
Summary: Cocoa powder has 624 mg of oxalates per serving. Limit cocoa powder or dark chocolate if you suffer from kidney issues.
8. Grits and Baked Potato
One baked potato has 97 mg of oxalates, and just one cup of grits contains the same amount per serving (12). Baked potatoes and grits can be a healthy part of a balanced diet, but if you have kidney stones or kidney issues, try to avoid, or limit your intake of potatoes.
Summary: A baked potato and 1 cup of grits contain roughly 97 mg of oxalates. If you have kidney stones, limit these foods. Instead of grits, opt for other whole grain choices, or swap mashed potatoes with mashed cauliflower to reduce oxalate intake.
Bulgur is a type of cereal that comes from the wheat species, most often durum wheat. Bulgur is often added to Mediterranean type foods like tabbouleh and dolmas (stuffed grape leaves). But it is also added to cereal, veggie burgers, and even foods like squash. Bulgur is also high in oxalates (12). Just one cup of cooked bulgur contains 86 mg of oxalates. Try to avoid this sometimes-common additive or limit your intake if you have kidney stones.
Summary: One cup of bulgur contains 86 mg of oxalates. Bulgur is a type of grain that is often found in Mediterranean cuisines, cereal, veggie burgers, and more. Swap out bulgur for other whole grains instead such as brown rice or quinoa.
Just a half a cup of beets contains 76 mg of oxalates per serving (23). Beets are a nutritious root vegetable that are naturally sweet (24). However, their high content of oxalates can be a problem for those who get frequent kidney stones. If you limit your intake of beets and you do not have a history of kidney stones, you will be fine.
Summary: 1/2 cup of beets contains 76 mg of oxalates. They are very nutritious, however, for those with kidney stones beets should be limited. Swap beets for other vegetables such as celery, carrots, parsnips, or artichokes.
A half a cup of navy beans contains the same amount as beets, 76 mg per serving (12), (25). Other beans are low in oxalates and safe to eat if you are prone to kidney stones. It is ok to eat lentils, green beans, and peas to avoid kidney stones (26).
Summary: Navy beans are the only bean high in oxalates, at 76 mg per serving. Beans are very nutritious and fiber-dense, so be sure to continue eating other kinds of beans for optimal health.
Kidney stones arise from many different things, but you should consider your diet if you suffer from recurring kidney stones or have kidney issues (27), (28), (29). Kidney stones are a serious medical condition that is usually passed naturally unless symptoms and the number of stones are severe (30). Make sure to avoid or limit these common foods and ask your doctor about your diet plan.
Try to examine your daily diet to make sure you do not get too much of these foods, and to make sure you eat a healthy balanced diet. Diet and lifestyle changes can significantly reduce your risk of developing kidney stones, especially the most common type, calcium oxalate kidney stones. These types of kidney stones largely arise because of an imbalance in the diet, so keep a close eye on what you eat daily.