Low Oxalate Diet File:Raphaël - Les Trois Grâces - Google Art Project 2.jpg


Do you need a low oxalate diet?

Who does?

Who does not?

How can you tell?

I chose the gorgeous painting by Raphael that hangs in the Musée Condé Chantilly because three surpasses one.

Who Needs Low Oxalate Diet?

Most of all, those whose stones contain calcium oxalate crystals and urine oxalate enough to promote such stones.

Less so those with systemic diseases – bowel disease, malabsorption syndrome, bariatric surgery, and primary hyperoxaluria – that raise urine oxalate. Their diseases require many treatments, only one of them low oxalate diet.

Therefore, I write here for only patients without a systemic cause of stones.

Do Your Stones Contain Calcium Oxalate?

If your stones contain little or no calcium oxalate crystals, and urine oxalate itself poses no danger to your kidneys, low oxalate diet is silly.

On the other hand, if your stones do contain calcium oxalate crystals, how much? Traces of the crystal, less than 10 percent, hardly bring it to the foreground. Even 20 percent is marginal. Above 10 or 20 percent calcium oxalate crystals in stones, consider lowering urine oxalate if high enough to raise risk of stones.

If you do not know what crystals make up your stones, struggle to find old analyses. Send all new stones for analysis. Stone prevention means crystal prevention. Stones are made from crystalsHow can you prevent what you do not know?

But if all this fails, assume your stones contain calcium oxalate crystals because they are the most common kindEven thenkeep trying to get a stone analysed; you have built your treatment on a rickety foundation because a guess is just a guess. 

Does Urine Oxalate Raise Your Risk for Stones?

It Does in General

In Gary Curhan’s wonderful study, the three bars represent two female (red) and one male cohort observed for decades. Some became stone formers, most did not. Twenty four hour urine samples drawn from both groups permit calculation of the risk from urine oxalate.

When below 25 mg/day urine oxalate poses no increased stone risk vs. even less than 20 mg/d. Thereafter, risk rises with urine oxalate, and low oxalate diet can contribute to stone prevention if stones contain significant amounts of calcium oxalate crystals.

Although Curhan had no stone analyses, calcium oxalate – being most common – would have predominated by chance. This is why if you do not know what your stones are made of, and your doctor has no clue either – from seeing them, or from observations during surgery, you can make the same assumption Curhan made and guess calcium oxalate predominates.

It May In You

Avoid circularity. That urine oxalate levels exceed, for example, 30 mg/day, does not raise the probability that calcium oxalate crystals comprise a majority of your stones.

It is when calcium oxalate crystals make up a significant proportion of your stone crystals – over 20 percent as a first approximation, or when you have no idea what your stones are made of but employ the Curhan conjecture favoring calcium oxalate that urine oxalate excretion matters. When above 25 mg/d you have a reason to lower it.

Be careful here. Follow the logic. Keep that oxalate list in the drawer for now and think about what you just read. If the trail of ‘ifs’ lead you on to urine oxalate as a suspect and you are in the right group – no systemic diseases, no kidney risk from oxalate according to your physician – continue reading.

Raise Your Diet Calcium

Diet Calcium Lowers Urine Oxalate

To illustrate the effects of diet calcium I have gathered average urine oxalate and diet calcium figures from multiple research papers named by senior author.

Dot size shows mean diet oxalate – the largest 200 mg/day, smallest 50, and middle 100 mg/day.

In each study raising diet calcium lowered urine oxalate. Diet oxalate itself had little effect.

The small box at the upper right shows an extreme experiment. Eating 2,000 mg/d of diet oxalate and 1,200 mg of calcium, subjects excreted 80 mg/d of oxalate. Despite the massive diet oxalate, enough diet calcium – 4,000 mg/d lowered urine oxalate to 30 mg/d.

Be careful. No one wants to eat that much calcium. The experiment simply aimed to make a point. My point is you eat 1,000 to 1,200 mg of diet calcium, and be done with it.

In other words, for any reasonable range of diet oxalate, diet calcium strongly controls urine oxalate. For that reason, measure the urine oxalate during high calcium diet and decide if low calcium diet remains important.

Diet Calcium Protects Bone Mineral

Even without stones we should want abundant diet calcium. Based on thorough reviews of mineral balance USDA and its scientific advisors recommend 1,000 to 1,200 mg of diet calcium daily for all US people as a benefit to bone health.

Because idiopathic hypercalciuria affects a majority of calcium stone formers they benefit especially from high calcium diet. Some people with IH cannot maintain bone mineral balance even on the high calcium intakes recommended for normal people. Less than high calcium diet poses risk of bone disease in later life.

Diet Calcium Should Come From Food 

Like most people, stone formers without systemic diseases do well with just dairy products and need no supplements. Industry makes them sans lactose, sans fat, in all the forms diet restrictions require. One might say the 1,000 or 1,200 mg of diet calcium best comes by parts in all the meals. If so, diet oxalate will encounter diet calcium by chance most of the time, so calcium can reduce oxalate absorption and thence urine oxalate excretion.

What About Supplements?

Like with high calcium foods, calcium from supplements lowers absorption of oxalate when they meet during a meal. No meal, they serve no purpose. Worse, they can raise urine calcium and risk of stone.

Lower Your Diet Sodium

If high urine oxalate raises risk of stones, so does high urine calcium. Both count. But raising diet calcium can raise urine calcium. So if all you do is eat more calcium you may not stop forming stones. You need to do one other key thing.

The trick, the smart move, the center of the center: Keep diet sodium as low as possible.

Red dots are normal people, blue stone formers with idiopathic hypercalciuria. For both, urine calcium rises with urine sodium, and urine sodium – more or less – reflects diet sodium intake. Each dot represents an entire published study group. 

Modern diet recommendations for US people consider 100 mEq/d (2,300 mg) of sodium the tolerable upper limit. These diet guidelines do not concern stones but rather high blood pressure and bone disease, but even so fit well with our needs. You would want to lower your diet sodium below 2,300 mg/d even if you formed no stones, for your blood pressure and general bone health.

In fact, the ideal diet sodium is far below 2,300 mg, at 1,500 mg – or 65 mEq if you prefer.

With care for diet sodium, high calcium intake need not raise urine calcium and certainly will lower urine oxalate. Lower urine oxalate without any rise in urine calcium means a fall in stone risk and therefore fewer stones long term.

Low Oxalate Diet Seems Easier


He tells me to obsess about my stone crystals, raise my diet calcium, and lower my diet sodium. Two diet changes!

Why not just lower diet oxalate in the first place and be done?

Low Oxalate Diet Serves Only One Purpose

Low oxalate diet provides no health benefits apart from stone prevention. The highest oxalate foods, some dark green leaves, have good nutritional value. No data support diet oxalate as cause of any significant diseases apart from kidney stones. If you need to rely only on low oxalate diet to lower your urine oxalate then the diet may need to be very strict and restrictive of otherwise good foods. Higher diet calcium makes it easier and allows for greater variety.

Low Oxalate Diet Has Never Been Tried as a Stone Prevention 

No one has yet published evidence that low oxalate diet itself prevents calcium oxalate stones. At most, trials of other agents or diets have specified some restrictions of diet oxalate.

High Calcium Low Sodium Diet Prevents Stones

US diet recommendations favor low sodium and higher calcium to prevent hypertension and bone disease. One formal trial proved this kind of diet prevents calcium oxalate stones.

That trial showed that a high calcium, low sodium diet reduced calcium oxalate stone recurrence in men with idiopathic hypercalciuria.

Over five years, stones were less (solid line) in men asked to eat 1200 mg of calcium, 200 mg oxalate, 65  mEq of sodium compared to men eating 400 mg/d of calcium, unrestricted sodium and oxalate (dashed line). The 200 mg of diet oxalate in the high calcium group was achieved simply by excluding very high oxalate foods like spinach and nuts.

Although diet calcium was twice as high, urine calcium in the low sodium group was the same as that of the low calcium controls (5.9 vs. 6.2 mmol/d). Even though diet oxalate was 200 mg/day, not very low, urine oxalate was lower in the high calcium group (333 vs. 411 umol/day – about 35 vs 43 mg/d) and it is this reduction that reduced supersaturation and presumably new stones.

So low oxalate diet has no trial but high calcium, low sodium diet has one trial, a positive one at that.

Low Oxalate Diet is Not Easy to Follow

I know that from the many comments on this site, from decades of practice, too. One can lower diet oxalate. Those who form calcium oxalate stones are well advised to be wary of high oxalate intake. But why strive to go below 200 mg of diet oxalate when you can just eat more calcium and less sodium which helps your bones and your blood pressure? Let us make that diet – higher calcium, lower sodium our goal. With it, you need not so much a ‘very low’ as a moderately low – 200 mg –  oxalate diet and that is enough.

Let Us Focus Elsewhere and Better

High calcium, low sodium, and moderate oxalate seems the best plan. There is a trial of it. Three separate factors all point at stone reduction. Two of them, low sodium and high calcium confer health benefits beyond stone disease. As part of a threesome, diet oxalate lessens in intensity. The ‘list’ needs contain only the highest oxalate foods. The budget of 200 mg/day is large enough to permit considerable freedom.

More important than everything I have said so far. Do not begin with a reach for the oxalate list. The list at best adds value for some patients. You may not be that patient. You may not have an oxalate problem at all. If you do, higher diet calcium and lower sodium may solve your problem with a minimal effort toward diet oxalate.

Put your money on the high cards, on the best horses, the best teams.

In case you wonder about the three goddesses, it is for the three fold plan: Higher diet calcium, lower diet sodium, moderate diet oxalate. Not so pretty as they are, but good enough.

9 Responses to “LOW OXALATE DIET?”

  1. Renee

    Hi Dr Coe,
    I would be lost without your and Jill for sure!!
    I have all the figures for Sodium, Water, Oxalates and Calcium, but is there one for Sugar? I have read women should not have more that 6 teaspoons of sugar a day. That is A LOT. I know sugar is bad for Calcium Ox stones, but is there a low figure amount we could have that would be safe?

    Also, it is all quite overwhelming as to have to count all this stuff. Is there anywhere on your website that would list sample menus for breakfast, lunch and dinner and snacks that WOULD be safe for us??

    It would be sooo much easier for us to be good if we could just follow along. At least to even get a look at what is safe without having to look up all the values each time of everything we are eating.

    There are Paleo, Gluten Free, Low fat and tons more cookbooks out there, but I have never seen a Kidney Stone cookbook. It is MUCH needed.

    Thankyou so much,

  2. Michele

    I tried a low oxalate diet and was miserable. I’m also diabetic and had some restrictions. Now I eat all foods in moderation and try and drink a glass of milk or eat cheese with foods high in oxalate. I eat nuts but not daily, olives and chocolate and I’m sure a million other moderately high oxalate foods. I don’t eat spinach or anything else from the high list except for nuts and chocolate which I’m not prepared to give up, so I limit them.

    • Fredric Coe, MD

      Hi Michele, Just be sure to do all three – the high calcium and low sodium; both may benefit your other conditions as well as control urine oxalate. Regards, Fred Coe

  3. Kathleen Parent

    Hi Dr. Coe…You answered my biggest question about oxalates. Aiming for 200 mg/d oxalates with high calcium of 1200 mg/d and 1500 mg/d sodium answers my questions all in one equation. It fills in the last part for me. Love your article. Thank you for all you and Jill have done for stone sufferers. We need you both!
    Thank you!

  4. Ron Quinn

    Thank you Dr. Coe. Very informative. I am working with my doctor on getting a handle on Calcium Oxalate and Acid Stones. Putting together a diet is tricky. Is there a book you can recommend?
    Thank you again. Ron

  5. Debbie Bastian

    Thank you Dr. Coe, I was getting ready to go crazy on lowering oxalates…So , before my last kidney stone episode ( and first!) I had been researching the benefits of cocoa – not the sugarared kind, just raw cocoa – and had been making these wonderful smoothies with frozen bananas, cocoa, a small bit of honey, a little bit of milk or yogurt. After the kidney stone, I quit all cocoa, as well as avocados and walnuts and almonds…And no more spinach , all favorites for me. I thought since my first stone was at age 60 the culprit was the cocoa…But from reading this, maybe not? If the cocoa is with plenty of milk or yogurt, does it cancel out the bad?

    Thank you so so much!

    • Fredric Coe, MD

      Hi Debbie, The message is simple: Lots of diet calcium with meals and as little sodium as possible will get you a lower urine oxalate and controlled urine calcium with a net gain. Be sure to retest on such a diet and be sure things are as you expect – diet is tricky. Smoothies are a common problem because they concentrate too much into too little. Try eating your foods as they come. As for cocoa with milk it should be fine – do it and check out the urine if that is to become a habitual snack. Regards, Fred Coe


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