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. Ben

    Hello Dr. Coe and thanks for your clear writing.
    I had one Ca-Ox stone 30 years ago – I was taking a lot of Vit C (don’t ask why!) and riding my bike in hot weather, probably dehydrated. No stones since. Now I am 61 yo healthy man. I am considering taking tumeric/curcumin supplements for knee pain. I also have osteoporosis. I eat carefully (near vegetarian, fresh food diet, about 80-120 mg oxalates/d) have a high Ca diet and am working to lower Na intake.I don’t think I’m a stone former, don’t know if I have hypercalcuria. Would adding tumeric/curcumin put me at risk? How much should I take? Thanks, Ben

  2. Russell Long

    Dr. Coe,
    I’m sure you’re somewhat familiar with HCA, which is widely available for appetite suppression but is also being studies for potential dissolution of kidney stones.

    Are you aware of anyone who has experimented with it for stones, and if so, what the results were?

    Thanks much!

  3. Sam

    Dr. Coe,

    Thank you for such a thorough read. I am a relatively healthy eater, 44 years old, and living in the “kidney stone belt” (NYC). After creating and passing a 4mm Ca-Ox stone last summer, which caught me utterly by surprise the night I returned from a long airplane ride (apparently a trigger, sometimes), I have been working on my health in this area. I had a 24-hr urinalysis last Aug, and by Feb all my numbers improved except the sodium.
    pH 5.5 to 5.9
    SS CaOx 7 to 3
    Ca24 178 to 155
    Ox24 45 to 32
    Cit24 646 to 748
    SS CaP .29 to .32
    SS UA 2.5 to .84
    UA 24 1.0 to .9

    I started with Potassium-Citrate, but didn’t take well to the side effects. So I began a religious course of fresh lemon water every morning, refilling the glass with the lemon rind throughout the day. I have now begun ionizing water with a pH stick (EHM is the company) to raise the alkalinity of the water I drink. Now that I’ve read your article, I’m paying closer attention to the Na24, which actually moved the wrong direction from 151 to 163.

    1) Can you explain the lemon process, turning more basic upon ingestion? Does it compete with the ionization of the water (counterproductive)? Should I not ionize the water? What about Apple Cider vinegar as well? Will this help? Does it too turn more basic upon digestion?
    2) If I understand correctly, by lowering my digestive sodium (Na24), my calcium absorption should actually increase but my Ca24 should go down a bit more?
    3) Is there more I can do to prevent idiopathic hypercalciuria?

    Thank you!

    PS: I stopped eating spinach. 🙁 But I can’t give up my unsalted mixed nuts in my morning yogurt.

    • Fredric L Coe, MD

      Hi Sam, Given your present low SS values, perhaps you do not need to do more. Lowering diet sodium will reduce your urine calcium further but it is already below the level known to confer risk of new stones. Reduced diet sodium lowers urine sodium by raising kidney calcium conservation. Citrus fruits contain citrate and citric acid, the former is metabolized to alkali, the latter is not. So the more ripe the lemon the more citrate, and the better the effect. As a person in the US, better health is served by lowering diet sodium below 100 mEq/d so if you could you should. Regards, Fred Coe

  4. Jeannette Hoessel

    Hi Dr. Coe,
    This presentation was awesome and clear! Thank you. My urine calcium has always been fine. I just turned 70 and was told I have borderline osteoporosis. My doctor has left it up to me as to whether or not to take the med he has prescribed: Alendronate Sodium Tablets 70 mg. This seems to go against everything I’ve been working toward to keep my oxalate stone from growing. In four years (since Jill’s course), I’ve had no change in my stone. Is I opt to take this med, one of the side effects if hypocalcemia. My urologist says my bones are important, so maybe I should take it but I might have to take a calcium supplement. Do you have any thoughts on this? Id love your opinion.

    • Fredric L Coe, MD

      Hi Jeannette, Given borderline osteoporosis the drug is optional, as your physician says. OF high importance is a high calcium low sodium diet, however, as there is one major study in women showing that combination helps prevent bone mineral loss. The study is summarized in this article you have written on. I would strongly hope you might follow such a diet and get a new BMD in a year to see progress. The 24 hour urine is crucial if you would know your success in the diet – it gives you the urine sodium which is the diet sodium absorbed, and a good sense of stone risk from a high diet calcium. Regards, Fred Coe

    • Ron beaudin

      Very good information. In layman’s terms if I’m correct. 1# Low sodium 2# higher calcium 3# watch the higher Oxalate foods. Is this over simplified? Or good. Just had a 9 mm stone removed( nightmare pain!) I must change my diet! I’m 60. Male. The urologist said the hardness of the stone was 1300, he told me ONLY Oxalate stones are this hard. I’m sending it in to be analyzed. Have another 1 and 2 mm but hardness is 186 only the urologist said these are uric acid stones most likely. Thank you!

  5. Pamela

    Thank you Dr. Coe. Your articles are very informative! I recently had a 8 mm oxalate stone surgically removed that was stuck, although thankfully not completely blocking the ureter. I have another 3 mm stone sitting in the kidney calyx that is still there. I typically don’t eat dairy products, and am vegan. I don’t eat a lot of sodium but I will keep an eye on sodium content and don’t salt my food. I am taking calcium citrate supplements, as well as magnesium supplements. I also make my daily morning smoothies with almond milk, but maybe there is a better option? My question is will the calcium citrate supplements give me the calcium that I need in order to reach my daily calcium goal? From your articles, it seems that I definitely need to be sure my calcium intake is adequate, and it may not be. Thanks for any suggestions you may have for one who doesn’t eat dairy but needs more dietary calcium.

    • Fredric L Coe, MD

      Hi Pamela, calcium citrate is certainly a way to get the extra calcium, and be sure to use it with your main meals to block oxalate absorption. But also be sure you have been fully evaluated. Don’t just alter your diet without evaluation. You never know what causes stones until you look. Regards, Fred Coe

  6. Janice Reithofer

    Is there any information out there for a Spinal Cord injured person who has to be tube fed so cannot vary their diet? Has a suprapubic catheter.
    His stones are formed due to reoccurring UTI’s, (struvite) frequent among paralyzed individuals. His PH is always 8 or over. Read that to avoid infectious stones that his urine must be more acidic – how? Has 4 ozs of lemon juice in his coconut water – has more than 2 ltrs of fluid daily. Read that the lemon juice actually makes the urine more alkaline – true?
    Just in Emergency with fever and UTI because he has a 9 mm stone stuck in his utterer plus other stones in his kidneys, he is awaiting surgery – AGAIN ( 6 in 3 and a half years) but delayed due to the COVID 19 virus.
    His stones only began to form a year and a half after he fell and became paralyzed C3/C4 due to cervical spinal stenosis – no problems before.
    Tried – low dose of antibiotics, Cranberries, D. Mannose, Mandelamine (found out PH had to be 5.5 , Is now irrigating his bladder with Renacidin 3 times a day which has actually reduced the catheter being blocked and was able to go over a year since his last surgery.
    Any suggestions – any research into tube feeding and SCI patients with reoccurring UTI’s and infectious stones?

    • Fredric L Coe

      Hi Janice, The struvite stones are being produced by the action of bacteria that hydrolyse urea – a normal urine constituent – into ammonia and CO2. The ammonia raises the alkalinity of the urine to very high levels, even 9 or more, and the CO2 becomes carbonate. Magnesium and ammonium and phosphate, all normal in urine, precipitate into struvite. Renacidin is a magnesium containing solution that can help dissolve struvite and is an excellent idea. The bacteria that make the crystal normally live in the soil and are part of a planet wide nitrogen cycle. Having evolved in soil they rapidly become resistant to antibiotics. His diet is not the cause and change in diet has limited ability to improve things, given the bacteria are so powerful. Acetohydroxamic acid is an oral medication that can block the enzyme in bacteria that hydrolyses urea, and the drug can stop struvite, but it has a lot of side effects. You might want to mention it to his physicians. Regards, Fred Coe

  7. Terri Jensen

    This was the best article you’ve written yet for those of us not in the medical field. Much easier to read. Thank you!


    Hello Dr. Coe, thank you for this clarification about this magic formula! My question is: Can CA-OX/CA-PHOS stone- formers take supplemental Calcium Citrate to “up” their intake of Calcium from foods? Most high Calcium foods are also higher in Sodium, making it difficult to reach the needed 1,000-1,200 mg. of Calcium daily. I am concerned about supplemental CA due to the problem of it contributing to heart disease per many published scientific articles. Is it safe to take the supplement?
    Kindest Regards, Jolie

    • Fredric L Coe

      Hi Jolie, Supplements must be taken with meals, but are reasonable. Because of timing needs they are trickier than calcium containing foods. As for heart disease, I do not know if supplements are a risk. If taken with meals they should be much like food calcium in being absorbed slowly. After all calcium is an atom, the same in food as the supplement except for absorption and the extra alkali. Milk and yogurt are very high in calcium per unit of sodium, so are the best choice. Regards, Fred Coe

      • Jolie Dodd

        Dear Dr. Coe,
        Thank you so very much for answering this vital question for me; medical doctors are so evasive concerning this topic and I really look up to you as a mentor and medical professional who answers the hard questions others seem reluctant to! God bless you for your caring heart to help others!
        With a grateful heart, Jolie

  9. Anne

    Hello Dr Coe, thank you for putting this into perspective. The prioritization of lowering sodium, increasing calcium before other aspects of the diet is so helpful. Sometimes it’s hard to make a decision with competing diet elements. Thank you, Anne

  10. Tracey Walsh

    Great article Dr. Coe, nice to virtually meet you. I find the best part was you telling us exactly what order to do things in. This is extremely helpful to me. The graphs are also quite handy in making the information easy to understand. I’ve enjoyed previous articles of yours, but I feel this one was the most east to understand and at the end I had the most clear direction. Thank you for all of your help.


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