THE KIDNEY STONE DIET

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If we put together everything on this site about diet for kidney stone prevention we get a reasonable and consistent image of one basic pattern. It is more or less what is ideal for idiopathic hypercalciuria and for reducing urine oxalate. It is the diet that has been used in the one major trial of diet for stone prevention. It accords with modern recommendations for the health of the American people. More or less, after all is said, there is only one diet plan that meets the needs for kidney stone prevention and we have called it ‘The Kidney Stone Diet.’

‘We’ are me and Jill Harris (pictured right).

Of course, we are speaking of the diet for treatment of idiopathic calcium stones. Stones from systemic diseases, like bowel disease, primary hyperparathyroidism, primary hyperoxaluria, are treated by treating those diseases, and that is a different matter altogether. But those are the exceptions. Of the millions of American people with stones, almost all are idiopathic.

There will be surprises. Diet oxalate always matters but less so than you might think once the full diet is in place. Calcium will seem odd to you unless you have been a frequenter of this site. Sodium will seem all too familiar.

Dissecting the Diet

Calcium

High calcium intake is essential for stone formers. They have bones and many have idiopathic hypercalciuria that can cause bone disease unless there is a lot of diet calcium intake. Oxalate absorption is greatly hampered by high calcium intake, if the calcium is eaten when the oxalate is eaten.

It is not only stone formers who need a lot of calcium. The new FDA diet recommendations include high calcium intake for all Americans.

How high is high?

More or less, throughout life, men or women, girls or boys, the range hovers between 1,000 and 1,200 mg daily. This amount of calcium is ideal for both protection against bone mineral loss from idiopathic hypercalciuria and reducing oxalate absorption. The unique part for stone formers is timing the calcium to go with the main oxalate containing foods during the day.

Sodium

Urine calcium follows urine sodium like a shadow. The lower the sodium the lower the calcium. In the one bone study that seriously looked at the matter, it was the combination of low sodium diet and high calcium diet that led to positive bone calcium balance – uptake of mineral into bone as opposed to bone loss.

So, what is ‘low sodium. The new FDA recommendations are an intake below 2300 mg (100 mEq for those of you who read lab reports). For those with high blood pressure – treated with drugs or not – 1,500 mg is ideal. For stone formers, the latter, 1,500 is ideal because it brings urine calcium of hypercalciuric people near the normal range, and also benefits those without hypercalciuria by making urine calcium as low as possible.

If 1,500 mg is the ideal for the kidney stone diet, 2,300 is the absolute upper limit, and people will more or less want to live somewhere in between, hopefully at the low end.

Refined Sugar

Refined sugar is sugar that has been extracted from plants into the white stuff you buy in bulk and add to cake and cookie and brownie recipes, and use to make candy. The sugar in plants and fruits is packaged along with fiber and released slowly so it is very safe. Once you extract it into white powder it is absorbed very fast. We are not made to use this well. Blood sugar and insulin rise a lot, fat is formed, and it is not healthy.

Jack Lemann first showed decades ago that simply eating 100 gm of glucose causes a rapid rise in urine calcium with – can you imagine worse? – a concomitant fall in urine volume so supersaturations rise extremely high. It is the perfect storm. Urine calcium of people with hypercalciuria rises a lot more than in those without it, so it is evil in family members of stone formers. Since about one half of the relatives of a hypercalciuric stone former will be hypercalciuric because of genetics, even the children are put at risk by high sugar intakes. The worst part is that hypercalciuria is silent until stones or crystals form, so no one can know.

Very reduced refined sugar intake is emphasized in the new government diet recommendations because of American obesity and diabetes. The recommendation is that less than 10% of all diet carbohydrates come in the form of added sugar which means very little sweets. This means sugars that are added to foods, not the natural sugars in fruits and some vegetables. The latter are absorbed more slowly and are safe. Obviously candy and cake and brownies and all the other good stuff is in the very bad category.

Protein

Our long and difficult review of the protein story make a main point. People absolutely need at least 0.8 gm/day per kilogram of body weight of protein and need no more than 1 gm/d/kg. WIthin that narrow range there is a measurable but modest effect of protein on urine calcium that can be neglected if sodium is controlled. So we see no physiological basis or trial evidence that ‘low protein diet’ is appropriate. By low we could only mean 0.8gm/kg/d. The one comprehensive kidney stone diet trial implies a low protein intake but in fact employed 93 gm of diet protein – which is a lot. The diet change was to make 40% of it be plant based. But there is no evidence that plant protein reduces stones or urine calcium compared to meat protein. Plant based protein sources are often rich in oxalate.

Oxalate

All things being equal we have advocated for a low oxalate intake between 50 and 100 mg daily. However Ross Holmes showed clearly that with very high calcium intakes such as 1,000 to 1,200 mg daily, absorption of diet oxalate is less and therefore the need for strict control is also less. In the one diet trial by Borghi diet oxalate was 200 mg/day but diet calcium was high and urine oxalate actually lower than in his contrast group with low calcium diet and less oxalate intake.

The ideal approach as best we can tell is to put in place the high calcium diet, aim for about 200 mg of oxalate, which is easier to accomplish than lower values, and measure the urine results. If despite high calcium intake urine oxalate is creating risk of stones then diet needs to be altered appropriately.

Some people seem to absorb oxalate more efficiently than others, so there are no fixed rules. Many have normal urine oxalate excretions without any diet change at all. Many who have undesirably high urine oxalate at their first labs will show a marked fall with the higher calcium intake and need no further restrictions.

Some will remain hyperoxaluric despite the calcium and it is for them that very restricted oxalate diets can be reserved.

One key is urine collections to see that calcium alone can accomplish for any one person.

The other key is timing. The diet calcium must come in the same meals that contain the bulk of the day’s oxalate. Without that precaution calcium might not work well in this regard.

Fluids

We have covered this topic completely. The urine volume you want is above 2.5 l/d, the amount of fluids needed is about 3 l/d and you just have to experiment to find the exact intake for you, and also allow for weather, occupation, sports. Obviously sugared fluids have always been unfavored on this site, and you need to avoid them. The other major issue is steadiness over the day and into the evening. Overnight we just take our chances in most cases.

There You Have It

The kidney stone diet is one thing: High calcium, low sodium, low refined sugar, normal protein, flexible oxalate management that depends on how high urine oxalate is once high diet calcium is achieved, and of course high fluids.

This site is rich in articles that pertain to the kidney stone diet – it was built in part for this purpose. The home page lists articles by topic and you can find there the ones you need. Here is a brief summary with links.

High calcium and low sodium: 1,000 to 1,200 mg calcium 65 – 100 mEq (1,500 to 2,300 mg) sodium and care about oxalate (50 to 200 mg/day) can be achieved using our list of foods that meet all three requirements. It is essential that calcium be taken in with the meals that contain appreciable oxalate.

Low refined sugar (below 10% of daily carbohydrate intake): This is best thought of as a major reduction in sweets – cookies, candy, sugared drinks, cake, pie. Fruits are not a problem, but smoothies that break up the fruit may liberate their sugars and overcome the ‘slow release’ properties of the intact fruits themselves. We did not write an article about this matter because it is simply to give up what many of us love.

Normal protein intake – this translates into 1/2 to 2/3 pound of meats daily for an average adult. For stones, the issue of red meat vs. fish or chicken does not matter. Vegetable protein sources such as soy are high enough in oxalate one cannot recommend them.

High fluids and how to get them are in many articles on this site.

When Do You Begin the Diet

To us there is no question it should be after even one stone. The diet accords with all modern recommendations. The only special features are attention to oxalate and to timing of calcium with oxalate containing foods. High Fluids are more of a task, but after one stone the one trial showed a marked reduction in second stone formation with urine volumes above 2.5 l/day compared to the 1 l/d of the control group.

A more subtle matter is family members. Idiopathic hypercalciuria causes both stones and bone disease, and is hereditary. About half of first degree relatives of hypercalciuric people with stones have the trait even without stones. Given this, and also that the kidney stone diet is benign and in line with what we all should be eating, why not make it the general family diet as well?

I (Jill), have recently put together a private FB page called THE Kidney Stone Diet.  It is a group that helps educate you on your physician prescribed treatment plans. I moderate it to keep it clinically sound.  Come on over and join the discussion!

390 Responses to “THE KIDNEY STONE DIET”

  1. Ryan

    Hey,

    I’m into bodybuilding and i’m 17 years old, I eat 1,6g/kg of protein a day which iw mostly meat based protein. Can I lower my risk of kidney stones by eating more plant based proteins?

    Reply
    • Fredric L Coe, MD

      Hi Ryan, No trials, but I would guess yes. The plant proteins will raise urine calcium less than animal protein. Dairy protein is the same – safer. Regards, Fred Coe

      Reply
      • Ryan

        Hi, thank you for responding toy comment. Are there any studies on plant proteins and the risk of kidney stones? I really want to be carefull with my lifestyle and don’t want to risk getting kidney stones!

        Reply
        • Fredric L Coe, MD

          Hi Ryan, Plant protein is less likely to increase stone risk, but all food derivatives are risky. So it is best to make your diet out of intact foods. For example some nuts have lots of protein and not a lot of oxalate, so are good choices. But the KS diet is based on variety, deliberately to avoid risk from over use of any one item. Regards, Fred Coe

          Reply
  2. Courtney A

    Hello,
    I came across the diet while looking for my 10yr old son. He’s had 5 stones, 3 surgically removed. We will be seeing a pediatric nephrologist in two days as he had an abnormal 24hr urine test. Would your recommendations be the same for a child? Also, his kidney is underdeveloped and in his pelvis (hugging the bladder) do you recommend sports or would that harm him more? Thanks!

    Reply
    • Fredric L Coe, MD

      Hi Courtney, In all probability he has genetic hypercalciuria. But in a child I hope his physicians make a thorough search for the more uncommon genetic problems. The abnormal kidney anatomy requires an expert in pediatric urology to be sure. Are the stones forming in the low lying kidney??? As for the kidney stone diet, of course he should eat it, everyone should. It accords with general US recommendations. Regards, Fred Coe

      Reply
      • Courtney

        Thank you for the response! Yes they are only forming in the low lying kidney. You were correct in the genetic hypercalciuria. He was put on potassium citrate twice daily as his is very low. They didn’t look into anything further but at his next appointment I will ask that they do. They did limit his sports to non contact but saw that coming with the pelvic kidney. As long as baseball is ok, he’s ok :). Any other specifics you can think of I should ask? They have him drinking 80oz of water a day which makes me feel like floating away.

        Reply
  3. Pamela Jo Montez

    Hello! My 17 yr old grandson had a kidney stone that was 90% brushite. He is also anemic, and very underweight. ( He has upj corrective surgery on both kidneys, with right kidney malrotation. His left kidney is grossly undersized with an 18% flowrate). I am wondering if BOOST would be ok to add to his diet for the iron and the protein. Thank you.

    Reply
    • Fredric L Coe, MD

      Hi Pamela, I am concerned that your grandson has significantly reduced overall kidney function and needs care from a skilled pediatric nephrologist. I would try to obtain such care as soon as you can. I would not use any kind of supplements, only food, until he has that kind of physician managing his care. The anemia could be from reduced kidney function. From this distance I am only guessing, and perhaps his physicians know that his right kidney is providing ample kidney function, so I may err on the overly worried side – but I may not. Brushite stones are very difficult to precent, so that same nephrologist will be important for that as well. Regards, Fred Coe

      Reply
  4. Bryan

    How long should I take Urocit-K 10? I’ve been taking it for two years twice a day. My citric acid level was 22. I’m having difficulty getting urologist to understand ordering 24 urine test. I’m going try a nephrologist. I live in a rural area.

    Reply
    • Fredric L Coe, MD

      Hi Bryan, I guess that depends on what you are taking it for. If for uric acid stones, it would be life long. Likewise if your urine citrate is very low and you produce calcium stones. If neither, and it is being used to raise a normal urine citrate to above normal for a while, it would not be long term. In any case, 24 hour urine samples are key – they give the citrate level and pH which citrate pills affect. Rural is not a problem as the main vendors can service people anywhere in the country. As for your level, if you mean your urine citrate is 22 mg/24 hours that is so extremely low it either an error or you have a very marked disorder, or it is not mg. Can you tell me the units??? Regards, Fred Coe

      Reply
  5. Mohammad Shoumik Saad Aarman

    Any evidence for increased risk of stone formation if calcium from foods exceeds 1200 mg / day?

    Reply
    • Fredric L Coe, MD

      No, not for a person at random, unless we are talking about massive excess: over 1600 mg/d. In a stone former, possibly. Fred Coe

      Reply
  6. ROSETTE MOSS

    Hello Dr. Coe – I just discovered this website and am so appreciative of the information. I am a 65 yo female with history of calcium-oxalate stones, and diagnosed a year ago with osteoporosis and hypercalciuria, also now with gluten sensitivity. I was told by a dietician that in order for protein intake to trigger bone formation one must eat a 30mg “bolus” in one sitting (my endocrinologist said to limit protein to ~75mg/day, which is more than 1mg/kg/day)…so I’m confused about protein. What are your thoughts about how best to consume protein to support bones? Also any other advice would be much appreciated. Thank you!

    Reply
  7. Marjorie A McDonnell

    Dr. Coe,

    Can you recommend a Urologist in the Charlotte NC area?

    Thank you!

    Reply
  8. Joi

    My husband has had a varied make-up of kidney stones since 1988 with 20 surgical procedures since 1993 – the most recent 9/29/21. We have worked with diets based on kidney stone type which has been taxing with unclear outcomes. Upon reading your overview and recipes, there is renewed hope that time invested will reduce kidney stone formation and improve overall health for both of us.

    Reply
  9. Mary

    Thanks very much for your reply, Dr. Coe! I’ll review my nutrition with my MDs and nutritionist. (One of my endocrinologists has referred to Karl Insogna’s work at Yale.) It’s not hard to hit .8 g/kg protein with 1200 mg calcium ( ex. 4 glasses of milk x 8 g protein is 32 g right there) since I do eat modest amounts of lean meat and fish. Your admonition about sugar is appreciated since it’s a dangerous short cut to weight gain!
    Thank you for your incredibly valuable contributions to this issue – with osteoporosis being an expensive problem in an aging population and hypercalciuria contributing to osteoporosis for a significant percentage of women (many with no hx of kidney stones), this is an important area deserving of more funding and attention. Thank you for sharing your expertise with the world and for helping me to navigate my care.

    Reply
  10. Mary

    Hello Dr. Coe,
    No stones so far but both father and brother had calcium oxalate stones. BUT spine dxa -3+, hypercalciuria: pre 12.5 mg HCTZ @ 1x/day, ave urine calcium 296, post HCTZ 4 yr ave urine calcium 193, sodium 8 yr ave 69. 1200 mg calcium/day from diet. 61 y/o. Adequate fluid per your target. Potassium good with diet. About to switch meds owing to marginal spine effect/dxa after 4 yrs bisphosphonate/CTX better but not suppressed enough. (Have 2 endocrinologists – one at HSS/NYC managing.) Question: does eating oxalates with dairy (as calcium) decrease calcium available to bone? How much should I care about oxalates beyond avoiding top offenders? Advised to gain weight (5’6″, 106 lb) but difficult with minimal nuts, sugar…and my wacko metabolism. Any thoughts (especially for follow up with nephrologist)? Would you recommend switch to chlorthalidone? (bp ~ 105/65, no issues HCTZ) Thank you, Dr Coe! ! Mary

    Reply
    • Fredric L Coe, MD

      Hi Mary, Diet oxalate is not important in affecting calcium absorption. Do not worry about oxalate in regard to bone disease. Given your slimness one issue in bone might be protein nutrition – too little. Sugar is not beneficial for bone, but protein is. I would ask my doctors if nutrition was optimal for bone health. Regards, Fred Coe

      Reply
      • Neena

        Hello Dr Cole do you have any recommendations for struvite stones. Also any suggestion on how to lower ph to more acidic environment. Thanks

        Reply
        • Fredric L Coe, MD

          Hi Neena, They arise from bacteria that produce them, and diet will not help. They need surgical removal and efforts to remove as much of the infected stone material as possible. Afterwards, your surgeons need to consider what can be done to prevent more infection and stone. Diet is to no avail. Regards, Fred Coe

          Reply

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