What Are Oxalates? How Tiny Compounds Can Affect Your Kidneys


Nutritionists often urge individuals to eat a rainbow of foods during meals: cherry colored tomatoes, emerald-hued spinach, and orange yams, to name a few. But many of these multi-colored veggie options include a compound that can actually suppress the absorption of key nutrients in your body. Before you pat yourself on the back for choosing a spinach salad as a side dish, take a peek into the little-known world of oxalates. Learn what they are, how they get into your body, and how you can avoid them to help maintain your kidney health.

What’s an Oxalate?

Oxalate is the chemical outcome of metabolism in plants, including meal planning favorites like potatoes, cocoa, and almonds, as well as spinach, rhubarb, and raspberries. Oxalate is a natural and important part of the regulatory functions in plants, and possibly even helps protect them from grazing by herbivores. In terms of oxalate levels, no two plants are alike; oxalate levels can vary within the parts of a plant. Oxalate levels depend on a variety of factors, including geographic location, seasons, and weather.

Researchers have found that plant oxalate levels are highest in a plant’s leaves, second highest in the seeds, and lowest in the stems. Researchers have also found that oxalate content increases as plants ripen.

Oxalate is found throughout nature. It’s produced in most edible plants and fruit, but also in the human body as part of normal liver metabolism. Although plants need it to thrive, oxalate has no known benefit to our bodies – it’s either filtered by the kidneys and excreted through the urinary tract, metabolized by our gut bacteria, or removed from the body through stool.

How Oxalates Affect Your Body

Oxalate is known as an anti-nutrient – a compound that decreases or blocks the absorption of vitamins and nutrients in your body.  Oxalate can bind with calcium, iron, and magnesium during digestion, blocking these essential nutrients from being absorbed by your body.  Complexes formed from oxalates binding with nutrients can also accumulate in your kidneys and become hard to filter out.  In small amounts, oxalate may not affect your health; however, if your diet frequently contains a variety of oxalate-packed foods, the oxalate overload may affect your kidney and urinary tract.

Low-Oxalate Foods to Choose

Following a low-oxalate diet doesn’t mean you have to avoid all fruits and vegetables. Cabbage, corn, cauliflower, cucumbers, squash, sweet red peppers, and iceberg lettuce are just a few low-oxalate veggies on the table. Low-oxalate fruits include cranberries, cherries, melons, seedless grapes, peaches, and plums.

Non-processed meat products contain low to no oxalate so lean-protein meats like chicken and turkey are good options for a healthy and low-oxalate diet. Other lean protein sources include fish, clams, and oysters. Vegetarians should be conscious of oxalate levels in plant protein. For vegetarians, black-eyed peas, green peas, and flaxseed can provide low-oxalate protein. Dairy is also a great choice for low-oxalate diets. Not only does it provide protein, but it also can help bind up some oxalate in the gut; thus, helping to remove it through the stool. So, enjoy that ice cream – but in moderation, of course.

Knowing the effects of oxalate in your food — and how to avoid it — is the first step to live a more kidney-friendly lifestyle! Making low-oxalate choices allows you to eat nutritious food while maintaining a healthy balance of the nutrients your body craves.

For more tips on choosing low-oxalate foods, download our shopping guide.