Of all the knowledge on this site, a tiny nugget of three well established facts has explosive power for patients and physicians. Put to actual use they let you prevent idiopathic calcium stones and preserve bone mineral.

If you do not want to read the article, I have made a VIDEO to tell you the story in about 13 minutes. On my iphone the video opens well and looks better horizontal. Please let me know if it does not work well for you. 

I have not been shy nor secretive. Article after article speak about the three, but always in context so other facts can distract one, as can superb but unmagical paintings from a few masterpieces hung on the same wall. I know some patients, some physicians, have fully grasped the crucial importance of the three, and put them to use. From the many comments I read weekly, I know many have not. So I am taken with a passion to redress matters.

Les Demoiselles d’Avignon, Picasso, 1907, Hangs in MOMA, NY. It is my choice of masterpiece. I deliberately cropped into the center as I love the abstraction and also want metaphor for limiting attention to a few essentials in the midst of a richness of details.

Because Spring has come to cold Chicago, I used my picture from some Springs ago. Partly it is the green ivy, partly reminiscence.

This is About Idiopathic Calcium Stone Formers

Cystinuria, uric acid stones, struvite stones – all these are to one side. Calcium stones from systemic diseases likewise. Physicians detect these and manage them. My focus is on the vast mainline of patients who form calcium stones without systemic disease.

The Three Essential Facts

Diet Sodium Controls Urine Calcium

If I could I would paint this on the sky, draw it on sidewalks across the world. It has been demonstrated by scientists for at least 70 years,

and how it happens is reasonably well known. I made this picture using published data from many sources, and I placed the original data and references within this site. The blue points are from calcium stone formers, the red from normal people.

Urine sodium is diet sodium, because we absorb almost all the sodium we eat, and excrete it in the urine. Urine calcium is not diet calcium. We absorb only 18 – 35% of the calcium we eat, and that absorption is regulated by the intestines, and by hormones like vitamin D. 

Stone formers absorb a higher percentage than normals, but that is not why their urine calcium is higher. It is higher because they have idiopathic hypercalciuria and their kidneys do not retain calcium as well. At the heart of idiopathic hypercalciuria is what this graph shows – urine calcium is abnormally sensitive to diet sodium. As you lower diet sodium from the average US value of 150 – 200 mEq ( 3500 – 4600 mg) to the present ideal diet sodium of 65 mEq (1500 mg), their urine calcium (blue) falls into the normal range. 

Not rarely my own patients seem disappointed when I begin their treatment with lower diet sodium. It seems so mundane, so like the common nostrum that we all eat too much salt. Many have had multiple 24 hour urine tests, and I make a crude pencil graph of urine calcium vs. urine sodium and show them their own behavior. That works, sometimes. Otherwise, they agree to so alter their food lives, but – I sense this – wonder at coming all the way to a professor for a dull seeming advice. They do not sense the power sodium has, even if I show them this graph – or their own.

Diet Calcium Controls Urine Oxalate 

I made this messy but remarkable graph from work other people have done and put the name of the main author below their dots. These were experiments with variations of diet calcium, on the horizontal axis, measurements of urine oxalate on the vertical axis and diet oxalate as the size of the symbols. The smallest symbol means 50 mg/day of oxalate, the largest means 200 mg/d, the middle size is 100. In the main article using this I placed links to the original data.

The data scatter but above 1,000 mg of diet calcium all four authors found only modest urine oxalate, 35 mg/d or less as mean values. Average US calcium intake is about 500 mg/d or less, which permits a much higher swing in urine oxalate. 

People with idiopathic hypercalciuria, the reason for high urine calcium in idiopathic calcium stone formers, absorb diet calcium more efficiently than normal, so a higher diet calcium supply will raise urine calcium and stone risk.

But, low diet sodium will offset this, improve kidney calcium conservation, so urine calcium can stay low even though diet calcium is high enough to lower urine oxalate.

This is part of the magic and the peril. You must lower diet sodium first and show it is low by another 24 hour urine. Then you can raise diet calcium to block diet oxalate. If you do it right, and keep the diet sodium low, urine calcium will rise little if at all with a higher diet calcium.

Diet Sodium and Calcium Control Bone Mineral

Only one trial proves this, and only in one kind of person – perimenopausal women. We could use more trials. But this one was so perfectly done, and so dramatic, we can for the moment use it as out guide.

Each woman ate each of four diets, high and low sodium, high and low calcium, and in a random round robin fashion. Specifically, the sodium levels were 1600 and  4400 mg/day, and low and high calcium (518 and 1284 mg/day. On each diet, each woman participated in a full balance study so bone mineral uptake or loss could be quantitated.

The four diets are on the horizontal axis. Calcium balance of bone is the black bars scaled on the vertical axis in mg/day, and it can be negative – bones are losing – or positive – bones are gaining calcium.

Absorption is plotted upward, meaning more for bone. Urine and intestinal secretory (‘endofac’) losses downward meaning potential losses for bone,

Balance was positive only with the high calcium + low sodium diet.

The amount of calcium absorbed was higher on the two high calcium diets, of course, and the urine calcium was lower on the low than on the high sodium diets.

As I have already said, the odd term ‘endofec’ means the amount of calcium secreted from blood into the stool by the duodenum, pancreas, and small intestines. This was measured using stable isotopes. If you look close, it was a fall in urine calcium and calcium secretion, both, that created the bone mineral gain from high calcium low sodium diet vs. the high calcium high sodium diet.

Also look close at the urine calcium. The high calcium low sodium diet gave the very same urine calcium as the low calcium high sodium diet. In other words, the women could raise their diet calcium from 500 to nearly 1300 mg/day and yet by lowering diet sodium to 1600 mg/day keep urine calcium unchanged.

The Magic Works for Stones

This is the one trial of the magic formula. Low diet sodium to keep the calcium in the body and thence the bones, high diet calcium to keep oxalate out of the body and thence the urine. It works for bones. Does it work for stones?

Of course, why else would I put it here, and many other places on this site.

I made the graph very large so your could see the printing in the overlay. The patients were men forming calcium oxalate stones whose urine calcium exceeded 300 mg/d. Low calcium diet was 400 the high calcium 1200 mg/day. The low sodium diet was aimed at 1150 mg, the high at the usual level of about 4000 mg/day.

After five years, stones were fewer in the high calcium reduced sodium group – highly significant statistically.

The why of less stones is exactly what my prior graphs predict.

Of course urine sodium was lower in the low sodium diet group (2,800 vs. 4,600 mg/d, low vs. high sodium, respectively).

Urine calcium of the low and high calcium groups was virtually identical (248 vs. 236 mg/d, low vs. high diet calcium, respectively). Just like for the women in the bone study, one could triple diet calcium yet keep urine calcium the same by lowering diet sodium.

Are you not amazed by this? In two studies one can raise diet calcium three fold and urine calcium does not increase if you also lower diet sodium. Look at the power diet sodium has.

How about oxalate?

Both groups were told to avoid high oxalate foods – walnuts, spinach, rhubarb, parsley and chocolate. The high calcium diet lowered urine oxalate (333 vs. 411 umol of oxalate/d, high vs. low diet calcium, respectively). Supersaturation for calcium oxalate, the proven driver of stone risk, was 3.5 in the high calcium and 4.5 in the low calcium group.

Think about how the threefold magic formula worked. Low sodium diet permitted high diet calcium. The high calcium lowered the oxalate but could not raise urine calcium because sodium was so low.

How to Use the Three Facts

These are magical facts, but they must be used in the right order. It is exactly like casting a magic spell.

Lower Diet Sodium First

Make the change and then be sure you did it by getting a new 24 hour urine. Without the urine test you will never know if you succeeded. Ask yourself if what you did during the collection was like the usual for you and also ask if you really mean to keep the diet sodium as low as during the test. If you get tired of the low diet sodium, and urine sodium rises, all is lost.

Raise Diet Calcium Next

Once you know your diet sodium is low, raise the diet calcium and test again. Is diet sodium (urine sodium) still low? If so, is urine calcium low enough? Low enough is about 200 mg/d of calcium or less.

If so, you are done. If not, you need to keep changing diet sodium and calcium until you get there – high diet calcium, below 200 mg urine calcium.

Some people cannot make do with only diet. Their urine calcium remains too high. For them, we add thiazide to the diet, usually in a very low dose. But for most, this will do. You must keep the low diet sodium, so the thiazide works well at a low dose, and to avoid potassium loss.

Now, Consider Diet Oxalate

With high diet calcium in place, is urine oxalate high enough to raise risk of stones – above 25 – 30 mg/d. If so, it is time to get rid of the highest food oxalate sources. Not all food oxalate, but foods on the high end. I listed some just above. My site has the main ones on a graph. Work from the top down.

Diet oxalate is the last thing to worry about, never the first. One wants to remove what high diet calcium has not removed.

Of course, repeat 24 hour urines are the only way to know if success or failure has attended your efforts.

If You Have Bone Disease

If your bone mineral is deficient, these diet changes are good but you need a physician to be sure they are enough. You may also need medication. Do not rely on just diet. Repeat bone mineral measurements are essential. Be sure your physician is satisfied with your bone health.

If you do Not Have Bone Disease

You may not have looked. Get a bone mineral density. If it is normal, get another some years later. The diet is fine for you unless bone mineral declines. If it does decline your physician needs to manage things. The diet is still advisable, but may not be enough.

There is More but Focus Here, on the Big Three 

Diet potassium and protein matter, the former from from fruits and veggies. Diet refined sugars matter, they raise urine calcium. Diet protein matters, too much raises urine calcium. The kidney stone diet accounts for all of these.

Fluids matter. Urine volume should be above 2 liters/d, the point at which stone risk has been reduced. But fluids are never enough.

But the three way magic spell predominates over all else: – lower diet sodium, then raise diet calcium, then consider diet oxalate.  

Keep your mind on diet sodium and calcium first, and be sure they are set properly. Then go on, if you must, into the thicket and brambles of oxalate lists. Then control unhealthy sugars, excess protein, and get adequate diet potassium. They matter, I always attend to everything I can.

But always, I urge, stay on the main road. Perform the magic spell and see how far you can get.


  1. James C

    Back on August 20 you asked me to respond with my location but there was (is) no “Reply” button alongside your comment. I sent emails to but received no response. On August 15 I had the stones removed for the 4th time. A followup cystoscopy on October 13th showed very little regrowth so I’m somewhat encouraged. For the record I live in Charlotte, NC and my Medicare coverage does not include your university. I’m currently trying to get into the Urology department at Atrium Health. Is there additional assistance you can provide. Thanks.

    • Fredric L Coe, MD

      Hi James, Sorry for the communication problem. Atrium is the only university provider in your area so far as I know and should be what you need. Regards, Fred

  2. Sami

    Hi Coe,
    how can i get rid from reoccurring kidney stones, I’m having since 2017 every years, and sometimes in a month’s.. there’s is no single doctor is helping me. All just say keep hydrated this is the only solution. i tried everything. i drink daily 4+ litre water + lemon juice, low sodium nothing difference… please help me.
    My all tests are normal except 24hrs CA that was 360 but PTH was normal.

  3. Antoinette

    I just received by 5mm stone analysis. 60% Calcium Oxalate Monochydrate, 30% Oxalate Dihydrate, 10% Phosphate apatite. I have been diagnosed with hypercalcuria and osteoporosis earlier this year. I was a few days away from starting on forteo when I had a stone attack (June 1,22). I had a Cystoscopy, Left retrograde pyelogram, Left ureteroscopy with laser and Left stent placement on string which was removed after one week. I have not had a follow up with surgeon. From his post-op notes he thinks I may have UPJ obstruction and I go for a renogram next week. May I deduce from the stone analysis that I have to watch my oxalate intake? What does one do for fiber? One can’t possibly their 25-30 grams without bran can they? What other tests might you suggest that will help me with my kidney health and decide on the best bone medication. I love your the quote “A stone clinic should also be a bone clinic” but it doesn’t seem that how it works around here. Thank you for all the wonderful, helpful information.

    • Antoinette

      Never mind about the fiber question, I just read Jill’s Your High-Fiber, Low-Oxalate Grocery List if I really do need to watch my oxalates. If you would be so kind to help me with my other concerns, it would be so appreciated.

    • Fredric L Coe, MD

      Hi Antoinette, No, oxalate is not your main issue, it is the hypercalciuria and perhaps oxalate if your 24 hour urine oxalate is elevated. Be sure you have been fully evaluated. Treat what is abnormal. For the hypercalciuria, as the article notes, reduced diet sodium is a first step. This permits high calcium diet without risk of raising urine calcium and stone risk, and also lowers urine oxalate. Lower diet oxalate comes last, if urine oxalate is high despite the high diet calcium. The article you wrote in on, in other words, is a very good choice. Regards, Fred Coe

      • Antoinette

        Hello and Happy Holidays Dr. Coe!
        Had all the testing and I am now on a low dose hydrochlorathiazide 12.5mg once daily for calcium in urine(322mg/24hr). So now to decide what bone med to be on. I have an endocrinologist suggesting fosamax and a rheumatologist suggesting forteo. No fractures. T-score of hip -3.0 and -2.9. Concerned about Forteo and the calcium issue. Do you have any thoughts? Thank you in advance. Antoinette

        • Fredric Coe, MD

          Hi Antoinette, Thank you. If your two bone physicians can agree, the bisphosphonate (fosamax) does not, and the Forteo does raise urine calcium and stone risk. So on balance perhaps the former might win out. But I am far away and they are not, so it is up to them to argue it out. Regards, Fred Coe

  4. EmRo

    This is a bit long….
    My family member has complicated and competing medical issues regarding nutrition. In early 2020, he had kidney stones removed by surgery. In May 2022 he had a complete abdominal ultrasound which showed NO stones. He takes a medication nightly that is sedating and can cause constipation (fortunately it doesn’t for him) and will cause high blood cholesterol and blood fats and may also cause diabetes, so he needs to watch his intake of fats, cholesterol and carbs/sugar. He is not very compliant, and his diet is high sodium as well. If he drinks 48 oz of water a day, that would be a lot for him. He hates fruits, the only fruit he’ll eat is canned pineapple, which is extremely high in oxalates.
    He had his gall bladder removed on June 17, 2022. He had diarrhea, once after surgery, then was fine for a week with normal bowel movements, now as of this note he has diarrhea (liquid) once daily. I have insisted that he contact the gall bladder surgeon ASAP regarding the diarrhea. For the week after surgery, he stopped taking a magnesium supplement (which he had taken for years) because he was concerned that it would exacerbate the diarrhea. It was immediately thereafter that he passed another stone, in urine, on June 28, 2022, in my opinion suspiciously while he was off the magnesium, which I was under the impression was helpful in preventing stones. His urologist disagrees.
    He restarted the magnesium at half dose and was fine, then went to his regular dose and got diarrhea the next day and has had diarrhea once daily since stopping the magnesium again. So currently the most pressing issue for him is what he can eat to calm down the diarrhea, which may be a result of the gall bladder removal because of bile dumping.
    His urologist gave him the following Kidney stone prevention advice.
    1. Drink at least 10, 10 oz glasses a day of liquid except for dark colas and tea.
    2. Limit sodium intake to <1,500 mg a day.
    3. Two fresh lemons or "real lemon" lemon juice/lemonade a day may elevate your citrate level and help prevent kidney stones.
    4. Most stones are PREVENTED with HIGHER calcium intake, so do NOT avoid calcium. We recommend at least 1 gm of calcium intake a day, (My family member's solution is to eat cheese. but cheese is high in salt, which I have told him many times. I have suggested drinking low fat milk instead of cheese). 5. No more than 8 oz of animal protein a day. (His nightly med makes him very hungry, and he eats large portions.) 6. Obesity is a big risk factor for stones. 7. Limiting some high oxalate foods, like spinach, nuts, berries, avocados and teas within reason- because in general these are very healthy foods and the benefits of consuming these foods usually outweigh the risks. Search foods that you consume daily or in high quantities to check oxalate content and try to reduce intake. (Only raspberries are very high in oxalates, as far as I know.)
    If we can’t get him to comply with diet, especially reducing sodium, and drinking copious amounts of water, what meds are available to help prevent stones and what are their side effects? How would a dietician/ nutritionist meet the competing needs of his dietary requirements? So many of the foods he should eat, he refuses to eat or are not compatible with a kidney stone prevention diet.

    • Fredric L Coe, MD

      Hi EmRo, I am afraid that you are flying blind in a cloud of competing GI and diet issues – or at least I am. What are the stones made of? What to the 24 hour urine collections reveal as to the cause of the stones? Diet prevention rests on principles but varies with the details of any one person. For example, is urine oxalate high? Do stones contain oxalate? Is urine volume or pH low from the diarrhea?? Your urologist is not out of line in recommendations but are they appropriate for this person. Like in carpentry – measure twice, cut once. Regards, Fred Coe

  5. Rajan

    Dear Dr Fred,
    I am a first time stone former and haven’t passed any yet – so cant be sure which ones but they are visible on both CT scan & Xray, so I am told these are Calcium Oxalate ones. I am in Dallas area and I can’t seem to find a urologist who specializes in Kidney stones removal and prevention. Do you know anyone like yourself in the Dallas area ? or do I need to travel to Chicago ?

    Many thanks

    • Fredric L Coe, MD

      Hi Rajan, In Dallas at UT Southwestern Dr Orson Moe is expert at medical stone prevention. Dr Peggy Pearle is a famous stone surgeon at the same institution. There is no need to come here when you have such talent right there at home. Regards, Fred Coe

      • Warren Maher

        Dear Dr. Coe,
        Since 2013, I have developed six kidney stones. I currently have three kidney stones, two in the right kidney, and one in the right proximal ureter. I am needing am more help with prevention than I am currently receiving. Please let me know of any qualified urologists in the Denver/Boulder Colorado area that you suggest to be of best benefit for me. Thank you.

  6. Denise

    I had my first stone at age 20, have had lithotripsy twice, have been stented twice, both my aunt and my sister are down to one kidney due to stones. The doctors I have had simply tell me to drink more water….can you recommend someone in the Milwaukee area or would I be best off to come down to your clinic?

    • Fredric L Coe, MD

      Hi Denise, Given the strong family history and stone surgeries I would advise decisive prevention beyond water alone. In Milwaukee the university is your best bet. Given telemedicine, I can ‘see’ you and offer consulting help (secretary 773 702 1475) to your physicians. Regards, Fred Coe

    • Fredric L Coe, MD

      Hi Denise, Given the marked family history I would recommend a full evaluation and a prevention plan based on what is found. In Milwaukee I would think the medical school is a safe choice. Given Telemedicine, I can ‘see’ you (secretary 773 702 1475). Regards, Fred Coe

  7. Loree Kowalis

    Dr Coe
    Retired nurse with pots syndrome, told to always add salt so now I have stone in kidney…Noone saying to address it, but I think I should.. I’m trying reduce salt, I also have osteoporosis dx…not done anything yet, Noone suggesting 24 hr urine or anything, let’s watch and see. I’d like to be proactive. Cut out spinach, high oxalate foods, reducing sugar, adding glass fairlife skim milk daily….I’m guessing bcs no 24 hr urine. Suggestions for potsie with dysautonomia ?

    • Fredric L Coe, MD

      Hi Loree, Given a stone, and bone disease I do not think it is ideal to do nothing. At least ask your physician to measure the density of the stone on CT as people over 50 (I am guessing here) may form uric acid stones. Likewise 24 hour urine testing, because there may be abnormalities one can reverse. Here is my article on stones in midlife. I would not change diet randomly – pointless. There is no obvious link between your autonomic nervous system disorder and stones. Regards, Fred Coe

  8. Peter K Seldin

    Dr. Coe,
    You treated me successfully for kidney stones when I lived in Chicago in 1981. You prescribed a maintenance drug that I took for maybe 20 years, before it was discontinued, and I did not have a stone during that period. I am now 67 years old, and I have had three calcium oxalate stones in the last 3 1/2 years after not having stones for a long time. I moved to CT in 1987 and went up to Yale for a few years, while I was still on your medication. Is it time to go back to Yale, or someone else whom you might recommend? Thank you for providing me with so many stone-free years. Regards,

    Peter Seldin

    • Fredric L Coe, MD

      Hi Peter, I do remember. I presume you stopped the drug and had more stones. Indeed you should be under treatment and there is nothing wrong with Yale. Fred

  9. Joan

    Hello Dr Coe,
    I have recently passed three calcium oxylate stones in six months. My kidney ultrasound shows bilateral hilar vascular calcifications. Can you recommend a specialist in the Norfolk or Virginia Beach Virginia area for me to see? Also do you have an opinion on Vit K possibly helping to actually reduce this calcification? If no, will it help stop further calcification? Thank you.

  10. Barry

    I want to make sure I’m understanding the levels of dietary sodium and calcium. I want to aim for 1500 mg sodium (or less, I assume) and 1000 mg calcium? Along with 2 liters of water per day. Is this correct?


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