You pay a lot of attention to which nutrients you put into your body for optimal fuel. But what if some of your go-to superfoods (think: berries, nuts, and spinach) contain compounds that not only sabotage some of your nutritional intake, but may also raise your risk for painful, race-stopping kidney stones? This can translate into the question: Is a low-oxalate diet for you?
Yes, it’s a real thing. Oxalates belong to a category of compounds dubbed “anti-nutrients” that block the absorption of nutrients. And unfortunately, they’re found in highly nutritious foods that probably make a regular appearance on your plate. Whole foods considered high in oxalates include:
- Fruits: berries, figs, kiwis, purple grapes
- Vegetables: spinach, Swiss chard, leeks, okra, rhubarb, beets
- Nuts, seeds, and grains: almonds, cashews, peanuts, soy, wheat bran, wheat germ, quinoa, chocolate, cocoa
So just how worried should you be and should you embrace a low-oxalate diet? Should you strike these foods from your menu entirely? Or is there a way to work around oxalates? Here’s what you need to know.
What Exactly Are Oxalates, Anyway?
Oxalates are a naturally occurring compound found in the human body and also in plants, where they function to help fend off bacteria and insects. Either way, our bodies don’t need oxalates, so the compounds typically join other waste products in food that are passed through the intestines and make their way to the kidneys to be excreted.
However, if you’re eating excessive oxalates, it can make it difficult for the body to get rid of them — especially if you’re not drinking enough fluids to sufficiently help flush them through your system. As oxalates build up, they can bind to calcium, blocking absorption of the mineral and forming crystals. In some cases, these crystals can continue to build until they form calcium oxalate kidney stones, the most common type of kidney stones.
Who Should Worry?
While eating an oxalate-rich diet may increase your likelihood of developing calcium oxalate kidney stones, it depends greatly on other factors, including what other foods are in your diet and your hydration status. Other risk factors include certain rare medical conditions like Dent Disease, and Inflammatory Bowel Disease like Crohn’s or ulcerative colitis.
The only true way to know if you have high levels of oxalates is through a urine test carried out by your healthcare provider. If your doctor does identify you as having a high risk for the formation of calcium oxalate kidney stones, here’s the good news: While you may need to limit high-oxalate foods in your diet, you don’t have to avoid them altogether — or miss out on all the other good-for-you nutrients they offer.
5 Tips to Minimize Oxalate Build-Up
Like many nutritional approaches, the secret to a low-oxalate diet is in the quantity, variety, and combination of foods that you eat. Work with your healthcare provider to determine how much you should limit oxalates in your diet, then try these additional recommendations for keeping buildup in check.
1. Pair High-Oxalate Foods with Calcium-Rich Ones
Eating foods that are high in calcium in combination with high-oxalate ones can help your body process the oxalates while decreasing the risk of kidney stones. The reason: Calcium binds with oxalates in the intestines — before they move into the kidneys and form stones — improving their excretion from the body. Here are some sample oxalate-calcium combos to try:
- Berries with yogurt
- Spinach or broccoli with feta cheese
- Quinoa and chia seeds with milk (to make overnight breakfast quinoa)
2. Steer Clear of Too Much Vitamin C
Ascorbic acid (vitamin C) breaks down in the body to produce oxalate, which can contribute to further accumulation. This can be a problem for people who take a vitamin C supplement every day, or for those who rely on vitamin C drinks as a primary source of hydration or to fight off colds. Unless prescribed by your doctor, avoid taking more than 500 mg of vitamin C daily.
3. Hydrate Well
Adequate hydration helps to flush the digestive system of toxins, so maintaining proper hydration helps with oxalate excretion. Aim to drink 1 ounce of water per day for every 2 pounds of body weight, so for instance, drink 75 ounces of water daily if you weigh 150 pounds.
4. Avoid Excessive Sodium
If you already fill up on whole, real foods and avoid highly processed ones, you are probably already eating an appropriate amount of sodium. On the other hand, if you tend to eat out often (two or more times per week) and reach regularly for packaged foods such as chips, crackers, deli meats, and soups, you may be getting too much sodium. Sodium causes the body to hold on to water, which counteracts the oxalate-flushing benefits of healthy hydration.
5. Cook Your Food
Doing so can lower the level of oxalates in foods such as leafy greens, according to a study in the Journal of Agriculture and Food Chemistry. It found that boiling in particular reduced soluble oxalate content by 30-87%. Steaming was less effective, which resulted in a 5-53% reduction, and baking showed no benefit, suggesting that the oxalates were released into the cooking water or steam.
Tips for a Low-Oxalate Diet
The idea of a low-oxalate diet is confusing. Restricting nutritious foods unnecessarily is stressful — it’s already hard enough to know how to eat healthy. And while high-oxalate foods can contribute to kidney stone formation in some people, the benefits of their nutritional profile generally outweigh the risks, particularly when you take the preventative measures outlined above.
Use these tips as inspiration to hydrate more, seek out calcium-rich foods, and make nutritious food combinations. And as always, consult with your healthcare provider about any health concerns, and try to enjoy the least restrictive diet possible made up of real, whole foods.
More Resources on Oxalates
Chai, W., and M. Liebman. “Effect of Different Cooking Methods on Vegetable Oxalate Content.” Current Neurology and Neuroscience Reports 53, no. 8 (2005).
Cleveland Clinic. “Kidney Stones: Oxalate-Controlled Diet.”
National Kidney Foundation. “Calcium Oxalate Stones."