Ask anyone who has had a kidney stone, and they'll tell you that it's one of the most unpleasant experiences they have ever had! Different types of kidney stones exist, but the most common is a calcium oxalate stone. In some people, calcium oxalate accumulates in their body and forms stones that must be eliminated through the urinary tract or in stool. In the United States, kidney stones affect one in 11 people, with higher rates among men, and overweight men and women.
If you tend to develop kidney stones, or if they run in your family, you may want to try a low-oxalate diet. Although a low-oxalate diet is commonly adopted by people who experience kidney stones, some experts also recommend it for autistic children. Preliminary evidence has linked a diet high in oxalate with autism; in some cases, experts recommend a low-oxalate diet as therapy.[3, 4, 5]
Here, we will describe how to start a low-oxalate diet, what you can eat, what to avoid, and the benefits of eating this way.
Quick Tips to Start a Low-Oxalate Diet
- On a low-oxalate diet, you will keep your consumption of oxalate in foods to around 40 to 50 milligrams (mg) per day. Some experts say that up to 100 mg per day is acceptable.
- When following this diet, you do not always have to avoid higher-oxalate foods. Your diet should consist mostly of low-oxalate foods with occasional medium- or high-oxalate items.
- Spinach has the highest oxalate level of any vegetable or fruit — more than 100 times higher than even most high-oxalate foods. On this diet, you'll need to avoid it!
- Most legumes are high in oxalate, but soaking them pulls the oxalate into the water (which you can then dump out).
- Boiling vegetables reduces their oxalate content 30 to 90 percent.
- Consume 800 to 1,200 mg of calcium per day when following a low-oxalate diet because it reduces how much oxalate is absorbed into the bloodstream.
- Limit your sodium intake because it increases the amount of calcium in your urine, which can lead to stones.
- If you are male, don't take high doses of vitamin C as it can increase your risk of developing stones.
What Is Oxalate?
Oxalic acid is a molecule that plants (and humans, actually) produce naturally and, as a result, it's in many plant foods. When it is bound to minerals — like calcium — it is called an oxalate. Although oxalate is present in plant foods, it isn't a nutrient. In fact, it's sometimes called an anti-nutrient because when oxalic acid binds to minerals like calcium, the body can't use those minerals. Second, oxalate is an insoluble crystal. When these crystals are small, they come out of the body easily. But, when they collect and grow in size, they're what we refer to as kidney stones, and they're painful and difficult to pass. Though other types of kidney stones exist, oxalate kidney stones are the most common.
What Increases Oxalate Levels?
Men who consume more than 1,000 mg of vitamin C (ascorbic acid) per day have a higher risk of forming calcium oxalate kidney stones. This is likely because the body converts vitamin C into oxalate.
Taking antibiotics may also increase oxalate levels. Antibiotics kill good gut bacteria that feed on oxalate. With less of those beneficial bacteria, more oxalate persists to form calcium oxalate stones.
Understandably, eating a diet high in oxalate is one thing that increases its level in the bloodstream and urine. If you tend to get kidney stones, you may consider this diet.
What Is a Low-Oxalate Diet?
A low-oxalate diet is, obviously, one that's comprised of foods that are low in oxalate. Many healthcare providers recommend this diet as a preventative measure for people who have developed kidney stones.
The average oxalate content of most diets is around 70 to 150 mg per day. On a low-oxalate diet, you will typically keep your oxalate intake at or under 40 to 50 mg per day. Although, some nutritionists say you can eat up to 100 mg of oxalate per day.[11, 12]
A low oxalate diet is recommended for people who are prone to or have developed kidney stones.
What Can You Eat?
When you follow a low-oxalate diet, you are not purely restricted to low-oxalate foods, as total consumption is what matters. Set a goal of keeping your oxalate intake below 40 to 50 mg per day. With planning, you can actually eat foods with medium levels of oxalate, or, occasionally, items on the high-oxalate list.
Also, think about portion size when considering whether to eat a high-oxalate food. For example, sunflower seeds are a high-oxalate food, but when you add a tablespoon of them to your salad, the serving size is small enough to provide valuable nutrients and a nutty flavor, while still keeping your overall oxalate levels low. On the other hand, when you eat multiple low-oxalate foods, it adds up.
The following vegetables are all low in oxalate. They are all good choices for someone following a low-oxalate diet.
|Green pepper||1/2 cup||5 mg|
|Mustard greens||1 cup||4 mg|
|Yellow squash||1/2 cup||4 mg|
|Cucumber||1/2 fruit||2 mg|
|Kale||1 cup||2 mg|
|Bok choy||1 cup||1 mg|
|Cabbage||1/2 cup||1 mg|
|Cauliflower||1/2 cup||1 mg|
|Peas||1/2 cup||1 mg|
|Zucchini||1/2 cup||1 mg|
|Chives||1 teaspoon||0 mg|
|Onions||1 small onion||0 mg|
|Romaine lettuce||1 cup||0 mg|
This list, while not exhaustive, provides some examples of low-oxalate fruits.
|Pineapple||1 cup||4 mg|
|Bananas||1 fruit||3 mg|
|Cherries||1 cup||3 mg|
|Limes||1/2 fruit||3 mg|
|Raisins||1 ounce (1 small box)||3 mg|
|Blueberries||1/2 cup||2 mg|
|Pears||1 fruit||2 mg|
|Cantaloupes||1/2 melon||2 mg|
|Strawberries||1/2 cup||2 mg|
|Apples||1 fruit||1 mg|
|Grapes||1/2 cup||1 mg|
|Mangoes||1 fruit||1 mg|
|Peaches||1/2 fruit||1 mg|
|Watermelon||1 slice||1 mg|
Low-Oxalate Bread, Cereal, & Grains
There are not many healthy grains that you can eat when following a low-oxalate diet. Processed white flour and wheat flour, as well as brown rice flour, are high in oxalate so do not eat foods made with either, including bread, pasta, and crackers. Wheat germ is also extremely high in oxalate, so avoid it.
Wheat and gluten-containing grains should be avoided anyway because gluten can cause digestive and systemic issues in many people. But even gluten-free grains like millet, brown rice, buckwheat, and quinoa are high in oxalate, and might need to be avoided on this diet.
The best choices for a low-oxalate diet are:
|Whole oat bread||1 slice||5 mg|
|Oatmeal||1 cup||0 mg|
Low-Oxalate Protein Sources
There are many plant-based sources of protein that are low oxalate. It's not necessary to rely on meat and endure the negative health effects it causes.[13, 14] In addition, raising animals for consumption harms the environment in numerous ways. The best protein sources are certain legumes — but not all. Most beans have high or at least moderate levels of oxalate, but if you soak them and then drain the water, oxalate levels in the beans are reduced.
Try soaking and draining beans to reduce the oxalate levels. Most beans will have high or moderate oxalate levels.
|Fava beans||1/2 cup||20 mg|
|Refried beans||1/2 cup||16 mg|
|Red kidney beans||1/2 cup||15 mg|
|Lentils||1/2 cup||5-10 mg|
|Garbanzo beans||1/4 cup||5-10 mg|
|Mung beans||1/2 cup||8 mg|
|Raw coconut meat||1/4 cup||<5 mg|
|Black-eyed peas||1/2 cup||<5 mg|
|Split peas||1/2 cup||5-10 mg|
|Lima beans||1/2 cup||5-10 mg|
Water is always the best choice of a beverage and, in fact, if you have kidney stones or are trying to prevent them, it's a good idea to increase your water consumption. Avoid draft beer or specially crafted beers, as they can be high in oxalate. On a low-oxalate diet, you can have the following beverages:
|Water infused with lemon||1 cup||0 mg|
|Pineapple juice||8 oz.||3 mg|
|100% Cranberry or Cran-apple juice||1/2 cup||<5 mg|
|Grapefruit juice||1/2 cup||<5 mg|
|Apple juice||1/2 cup||<5 mg|
|Brewed coffee||1 cup||<5 mg|
|Herbal tea||2 cups||<5 mg|
|Wine||1 cup||<5 mg|
High-Calcium Foods to Eat
Sometimes people see the name "calcium oxalate stones" and think they must avoid foods with calcium. Nothing could be further from the truth. Increasing your dietary intake of calcium will actually reduce the amount of oxalate in your body.
When calcium binds to oxalate in your intestines, it's more likely to be excreted in your stool before making its way to the kidneys.
Did you know, increasing your calcium intake reduces the amount of oxalate in your body.
Try to get two to three servings of calcium with each meal. If you eat a food that is high in oxalate, pair it with a high-calcium food. You can also get your calcium from certain vegetables or supplements.
Some studies link calcium supplements to higher stone formation rates — but only in people who already tend to get kidney stones, and this research is controversial. Experts recommend getting your calcium from food or taking calcium supplements with meals to minimize the risk of stone formation.
Avoid These High-Oxalate Foods
The good news is that you can still eat many foods on a low-oxalate diet.[11, 16] Below, we've listed common foods that are high in oxalate content. Occasionally, you can eat some of these, but do not eat them regularly if you are following the low-oxalate diet.
|Spinach, raw||1/2 cup||656 mg|
|Rhubarb||1/2 cup||541 mg|
|Buckwheat groats||1 cup||133 mg|
|Almonds||1 ounce (22 nuts)||122 mg|
|Corn grits*||1 cup||97 mg|
|Baked potato with skin||1 potato||97 mg|
|Beets||1/2 cup||76 mg|
|Navy beans||1/2 cup||76 mg|
|Cocoa powder||4 teaspoons||67 mg|
|Cornmeal*||1 cup||64 mg|
|Okra||1/2 cup||57 mg|
|Cashews||1 ounce (18 nuts)||49 mg|
|Raspberries||1 cup||48 mg|
|Soybeans*||1/2 cup||48 mg|
|Walnuts||1 cup||31 mg|
|Dried pineapples||1/2 cup||30 mg|
|Orange||1 fruit||29 mg|
|Sweet potato with skin||1 cup||28 mg|
|Grapefruit||1 fruit||24 mg|
|Soy milk*||1 cup||20 mg|
|Avocados||1 fruit||19 mg|
|Celery||1/2 cup||19 mg|
|Pumpkin seeds||1 cup||17 mg|
|Black tea||1 cup||14 mg|
*Best avoided at all times.
One study found some foods raise urine oxalate levels more than others, even ones with a higher oxalate content. These foods include spinach, rhubarb, beets, nuts, chocolate, tea, wheat bran, and strawberries. Although these foods offer important nutrients, they're best avoided if you follow a low-oxalate diet.
Low-Oxalate Diet Meal Plan
The following is an example of what a low-oxalate diet might look like:
- Breakfast: Chickpea scramble, coffee
- Lunch: Greek salad with cucumbers, tomatoes and raw organic goat cheese with vinaigrette dressing
- Dinner: Lentil chili, sliced pineapple for dessert
- Breakfast: Plain coconut milk yogurt with sliced banana and blueberries, coffee
- Lunch: Roasted butternut squash topped with raw organic goat cheese
- Dinner: Cooked black-eyed peas tossed with sautéed celery, red peppers, and onions in a vinaigrette dressing, fresh cherries for dessert
- Breakfast: Blueberry smoothie with banana and pea protein
- Lunch: Romaine lettuce salad with avocado, cucumbers, mushrooms, and vinaigrette dressing
- Dinner: Pumpkin soup
Other Natural Ways to Reduce Oxalate
There are several easy ways to reduce your oxalate levels, from drinking water to lowering your salt intake.
Drink Plenty of Water
When you drink a lot of water, your urine becomes less concentrated with substances that can cause kidney stones. The extra fluid intake causes you to urinate more, which means that oxalate is less likely to settle in your kidneys, bind together, and form stones.
One study found that people who produce between 2 to 2.5 liters of urine a day are 50 percent less likely to have kidney stones than those who urinate lesser amounts. In order to produce 2 to 2.5 liters of urine a day, you need to drink about eight to ten 8-ounce glasses of water.
Reduce Salt Intake
When you consume more salt, calcium concentrates in your urine resulting in a greater chance of developing oxalate stones. Try to limit your daily salt intake to 1,500 mg. To do this, you will need to read nutrition facts labels.
Many processed foods, such as canned food, fast food, and deli meat, are high in sodium, so avoid them — they are generally bad for your health anyway.
Limit Vitamin C Supplements
On a low-oxalate diet, you'll need to limit your vitamin C supplements. One study found that men taking 1,000 mg of vitamin C per day had a higher risk of developing calcium oxalate kidney stones than those who did not take vitamin C supplements. Women who took the same amount of vitamin C did not have a greater risk of kidney stone formation, nor did men who took lower levels of vitamin C.
The researchers recommend that men who tend to form kidney stones reduce their intake of vitamin C supplements. Dietary intake of vitamin C — in other words, vitamin C from food — was not associated with kidney stone formation in men or women, though few participants in the study consumed more than 700 mg per day from diet alone.
Consume More Citric Acid
You can find citric acid in many fruits and vegetables, especially lemons and limes. Citric acid can reduce your chances of developing calcium oxalate stones. When citric acid binds with calcium in the urine, it prevents it from bonding to oxalate. Citric acid also binds to existing calcium oxalate crystals, preventing them from getting larger, which means they are easier to excrete in urine.
How to Get Started
Begin by keeping a food diary and using online resources to calculate how much oxalate you typically consume. Next, start looking at charts of low-oxalate foods and look for opportunities to replace a high-oxalate food with one that is low in oxalate. If you have many high-oxalate foods in your regular diet, try switching to moderate-oxalate foods and then to low-oxalate ones.
Points to Remember
Oxalate forms when oxalic acid in plants binds with a mineral, such as calcium. Oxalate can create kidney stones in some people. A low-oxalate diet is one way to reduce your risk of developing calcium oxalate kidney stones. Some experts consider a low-oxalate diet a promising therapy for autistic children, as well.
Followers of a low-oxalate diet should keep their consumption of oxalate around 50 to 100 mg. You can do so by consulting many of the charts available that list low-oxalate foods. In addition to a low-oxalate diet, you may also want to increase your consumption of water, calcium, and citric acid and decrease your salt intake.
If kidney stones are or have been an issue for you, check out our article about the best remedies for kidney stones. It has more than a few good tips to help support normal, healthy kidney function.
Is a low-oxalate diet something you've tried or considered? What insight can you provide? Leave a comment below and share your thoughts with us.
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†Results may vary. Information and statements made are for education purposes and are not intended to replace the advice of your doctor. If you have a severe medical condition or health concern, see your physician.