Watercress and kidney stones; what’s the connection?

Oxalate is a waste product of the body’s metabolism but is also found in many foods including peanuts, rhubarb, spinach, beets, Swiss chard, chocolate, sweet potatoes- and watercress.

I didn’t plan to write a blog about watercress, despite the name, which is a play on words-my family name, Cress, and attributes of watercress -green, plant, tangy, nutritious, aquatic.

But people searching the web for information about watercress find this blog and the most common questions they need answered include

  1. Does watercress cause kidney stones?
  2. Can I eat watercress if I’ve had kidney stones?
  3. Does watercress cure kidney stones?
Big rocks on a grassy slope
These are stones. Kidney stones are called renal calculi.

What are kidney stones?

Stones, or urinary tract calculi, don’t usually cause symptoms as long as they stay in the kidney. But if they migrate down into the ureter, the tiny tube that connects the kidneys to the bladder, trouble begins. As the stones try to wiggle their way down the narrow passageway, spasms of pain result; and the bigger the stone the worse.

kidneys and urinary system graphic
The urinary tract- kidney, ureters and bladder

Fortunately, most stones less than 10 mm, or about 3/8 of an inch, eventually pass into the bladder and out the body through the urethra. Some get stuck and must be removed. Occasionally, large stones can block the kidney, leading to infection. But , once you have had a stone, you want to prevent another.

What causes kidney stones and why care about oxalate?

We know what substances cause most stones- chemicals that normally pass through the urine but  sometimes build up, harden and form into tiny rock-like structures called calculi. Calcium causes 95% of calculi, while the other 5% are made of uric acid, struvite, or cystine.

Calcium can’t travel out of the body alone, it needs a companion, either phosphate or oxalate. So people who have too much oxalate in their blood are at risk of calcium oxalate stones, the most common type- either from

Watercress and oxalate

Oxalate is a chemical composed of carbon-C and oxygen-O molecules. It combines with other elements to form salts, one of which is calcium oxalate.

Oxalate is a waste product of the body’s metabolism but is also found in many foods including fruits and vegetables, nuts and seeds, grains, legumes, and even chocolate and tea. Some examples of foods that have significant levels of oxalate include peanuts, rhubarb, spinach, beets, Swiss chard, chocolate, sweet potatoes- and watercress.

So to answer the questions-

  1. No watercress itself does not cause kidney stones, but the calcium and oxalate in watercress can.
  2. It depends. If you did not have a calcium oxalate stone and are not prone to that type, you should be able to eat watercress with no worries. If you have had multiple calcium oxalate stones, especially if they were large and required surgery, you may want to avoid any oxalate containing foods at all.
  3. Not exactly, but the calcium in watercress binds oxalate , removing it from the body in the urine. So there is less oxalate to make more stones.

Watch a video about kidney stones from MedlinePlus , and to watch in Spanish use this link en espanol- Cálculos renales

How to limit intake of oxalate rich foods.

If you do choose to avoid high oxalate foods, this chart from the National Kidney Foundation will help you choose the right foods.

Other ways to prevent kidney stones

Drink enough water to produce 2-2.5 quarts/liters of urine every day.

A high fluid, preferably water, intake can prevent build up of these stone causing chemicals. At least 2 quarts/liters daily is recommended, more if one does heavy physical activity , sports, or lives in a hot climate.

Limit the amount of sodium-salt-in the diet.

Since the majority of stones contain calcium, it might make sense to limit calcium. Calcium oxalate is a salt, but another important salt is sodium chloride, regular table salt.

The kidneys spend more time filtering sodium; so with less sodium, more calcium can  be flushed away and so it’s not making stones.  Here are 5 tips to reduce salt intake from WebMD. (They also help lower high blood pressure.)

Limit intake of certain animal proteins.

High purine foods can cause the less common uric acid stones. To prevent uric acid stones, cut down on high-purine foods such as red meat, organ meats, beer/alcoholic beverages, meat-based gravies, sardines, anchovies and shellfish.

a basket filled with fruits and vegetables
a LIGHTSTOCK.COM image, an affiliate link for stock photos and other media

Eat a whole foods, plant based diet.

Although watercress and other greens contain oxalate, it’s probably not necessary to avoid them entirely; they also are a good source of calcium which attaches to the oxalate, removing both from the body. Moderate amounts with adequate fluid intake should be safe, unless your doctor tells your otherwise.

  • Follow a healthy diet plan that has mostly vegetables and fruits, whole grains, and low-fat dairy products.
  • Limit sugar-sweetened foods and drinks, especially those that have high fructose corn syrup.
  • Limit alcohol because it can increase uric acid levels in the blood and avoid short term diets for the same reason.
  • Drink beverages with lime and lemon juice.

This information is current as of the publication date; it is general medical information that helps doctors and patients make decisions about what is right for them. Medical recommendations and practice change as we learn new things. Discuss with your physician or appropriate healthcare provider.

Explore further

This was a simple explanation about kidney stones but you can get more detailed info at these links.

the National Kidney Foundation

Explore the causes of excess oxalate in detail, especially the rare genetic causes, at the Oxalosis and Hyperoxaluria Foundation.

Doe and Faun White-tailed deer drinking at a farm pond in Stanly Co., NC on Aug. 19, 2000.
Doe and Faun White-tailed deer drinking at a farm pond in Stanly Co., NC on Aug. 19, 2000. copyright Daniel E. Wray

I don’t know if deer get kidney stones, but if so, they are doing the right thing. I like this photo from the LIGHTSTOCK.COM collection. (affiliate link)

exploring the HEART of health

Thank you for joining me to explore the HEART of health. I hope you’ve learned something new about kidney stones; I hope you never have one!

Dr. Aletha


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