A Remarkable Concordance
From 1980 to now the US government has published diet recommendations for the American people. Gradually and over time these have become quantitative and specify amounts of critical nutrients such as calcium, sodium, refined sugar, protein, and potassium – as alkaline anions in mainly fruits and vegetables. The goals are reduction of osteoporosis, hypertension, obesity, and diabetes. I shall call this the Ideal US Diet.
Surprisingly, though aimed at stone prevention and management of bone disease from idiopathic hypercalciuria, decades of kidney stone research have identified precisely the same diet. Even more surprising, the Diet Against Systolic Hypertension (DASH) diet resembles the current Recommended US Diet, and stone researchers have found a reduced risk of stone disease in people who eat ‘DASH – Like’ diets.
Is it possible we have come upon the Ur diet?
Research on three different problems – kidney stones, systolic hypertension, and healthy eating all end up with the same basic diet plan; is that plan the solution to an ancient riddle?
Ur diet or not, experts advise all Americans, hypertensive or not to eat the ideal stone prevention diet. Any stone patient can be advised to eat it, after even a single stone. You do not even need a stone.
Here is the science that says any stone former is well off eating this remarkable diet.
The other articles on the diet and the article on treatment of idiopathic calcium stone formers are good additions.
‘Still Life with Cheeses’, Floris Claesz Van Dijck, 1610, shows how healthy diets are not so modern. Note the fruits. The painter was well known for banquet still life paintings in which he pioneered.
Shared Features of the Kidney Stone and Ideal US Diets
The Principle Components
In the table, under the middle heading ‘TREATMENT’, ‘high’ and ‘low’ refer to changes from what is common now in the US but considered ideal as a future norm.
For the general health of the US nation, high calcium diet helps maintain bone mineral; low sodium intake and high potassium intake reduce blood pressure; low refined sugar helps stave off obesity and diabetes. A reasonable range of protein intake maintains nitrogen balance without imposing unneeded calories. Apart from potassium, fruits and vegetables provide high nutrient value with modest calorie costs.
Because idiopathic hypercalciuria causes negative bone mineral balance at present calcium intakes, high calcium diet can protect against fractures.
High calcium diet reduces absorption of diet oxalate so restriction of intake can be less onerous.
Low sodium intake reduces urine calcium, and also aids in achieving bone mineral uptake.
Refined sugar causes spikes of high urine calcium excretion that are best avoided.
Excessive protein intake raises urine calcium.
Diet potassium from fruits and vegetables is mainly potassium with organic anions that can be metabolized to bicarbonate and therefore increase urine citrate.
Oxalate and Fluids
Oxalate is important only for kidney stones but the healthy diet helps because high calcium intake lowers oxalate absorption. Rather than begin with cumbersome food oxalate lists I suggest patients raise their calcium intakes and then get a new 24 hour urine collection. Often urine oxalate will no longer pose stone risk. If it does despite high calcium intake and timing of high calcium foods or calcium supplements with meals, then is time enough for the lists.
I am quite the opposite about fluids. Any stone former is wise to achieve 2.5 liters of urine volume daily, which usually means 3 liters of intake. Nothing can more precisely undo the urine supersaturation kidneys achieve by water conservation than fluids enough to obviate a need for them to do it.
Components Secondary to Stone Prevention
The US diet plan is rich in fruits and vegetables as a way of controlling calorie and fat intake, and offering alternatives to high sugar desserts. The diet also emphasizes reduced fat intake and especially saturated fat, limitations that are irrelevant to stone prevention.
But I advocate for using the intact diet as opposed to only those aspects of it related to stone prevention. It is a coherent plan of nutrition whose structure that may help people create and maintain desirable eating habits.
High Calcium Intake
Let me again emphasize: ‘High’ and ‘low’ in what follows compare the desired diet to what is the common pattern right now in the US.
IH Bone Disease
Stone formers fracture at abnormal rates. Among people living in Rochester, Minnesota, the cumulative incidence of vertebral fractures in people with stones (irregular line) exceeds the rate of fractures in the entire population (the smooth line) between 1950 and 1974. Hip and forearm did not fracture excessively.
One can find two reasons for such fractures. The first is idiopathic hypercalciuria. The second is self imposed or iatrogenic low calcium intake in hopes of stone prevention. The US health recommendations for 1000 to 1,200 mg of diet calcium daily arise from massive research showing such diets help prevent bone disease in large populations. It will help stone formers especially, because people with IH cannot maintain neutral bone calcium balance as well as average unselected people, at least in part because of inefficient renal calcium conservation.
On the graph to the right those with IH are in red, those with normal urine calcium are in blue. ‘IH’ here is the research criterion of the upper 90th or 95th percentile of normal, so the urine calcium of the IH cases would approximate 250 and 300 mg of urine calcium daily for women and men, respectively. Even at calcium intakes of 1,200 mg/day the average calcium retention (red line) of those with IH thus defined barely reaches 0 – stable bone mineral content.
The US recommendations will hardly suffice for the most marked hypercalciuria and the lower calcium intakes in present use have the potential to cause bone mineral loss and eventual fractures.
Reduction of Urine Oxalate
Urine oxalate can rise because of genetic defects or bowel disease, which each have their own special place in stone prevention. But most people with stones have urine oxalate excretions dominated by diet oxalate content and intestinal oxalate absorption.
This latter is dependent on diet calcium. In the graph to the left, diet calcium is on the x axis and urine oxalate on the y axis. Each point represents values from trial data in which diet calcium was altered and urine oxalate measured. Oxalate intake varied from 200 to 50 mg/d and the symbol size reflects it. The data for the trials are available from the main article I wrote about this topic. The names are those of the principal investigators.
As diet calcium increases, urine oxalate falls more or less independent of oxalate intake. At 1,200 mg, most points are between 25 and 35 mg/d.
This does not mean that we no longer need to be concerned with diet oxalate. But it does mean that the recommended US diet calcium intake of 1,200 mg/d lessens the needed stringency.
In the small inset box, Hess makes this point with considerable drama. He gave people 2,000 mg/d of oxalate, a shocking amount, with 1,200 mg/d of diet calcium. Despite the drastic diet oxalate excess, urine oxalate was only 80 mg/d – too high of course, but consider the intake. He raised the calcium intake to near 4,000 mg and brought the urine oxalate down to near 30 mg/d. This is a powerful demonstration of how diet calcium can more or less balance diet oxalate.
From the graph, we can say that at about 1,200 mg/d diet calcium, diet oxalate can be in the range of 100 to 200 mg/d which is not very restricted. The exact relationship between urine oxalate and diet oxalate on this 1,200 mg/d diet might well be quantified by another trial, which could be of moderate duration.
Low Sodium Diet
Lowers Urine Calcium
One would be correct in saying that high diet calcium will increase urine calcium but the lower sodium content of the kidney stone diet will lower urine calcium and permit high diet calcium that protects bone and lowers urine oxalate.
Urine calcium varies with urine sodium in normal people – the red circles and triangles on the graph to the right. But the variation is much more marked for people with IH (blue circles and triangles) as defined by 95th percentiles as mentioned above. Circles denote prospective trials in which diet sodium was deliberately varied, triangles observational data. The non parametric ellipses contain 66% of the data.
Because the difference between IH and normal is in the slope, as diet sodium falls and lowers urine sodium – more or less, urine sodium is diet sodium on average – the two curves come together. A formal analysis of the slope difference is in the detailed article that presents these data.
At the US diet upper boundary of 100 mEq/d (2,300 mg/d) diet sodium, urine calcium in IH begins to overlap in part with normals. At what has been called optimal (65 mEq/d or 1,500 mg/d) diet sodium, the overlap is even better.
A single but well done trial of 1,200 mg calcium and 50 meq/d sodium (they actually ate about 120 mEq/d on average) was much more effective in preventing stones than was a low calcium high sodium diet – 400 mg/d calcium and uncontrolled sodium which was about 200 mEq – a diet that many people may be eating in the US today. More to the point, the urine calcium excretion of those eating 400 mg calcium and 200 mEq of sodium was the same as those eating 1,200 mg of calcium and 120 mEq of sodium. All of the subjects were males with calcium oxalate stones and IH. This trial is detailed in another article.
Improves Bone Mineral Balance
To date no trial has tested treatment of IH bone disease, but this one trial concerned menopausal osteoporosis and used high calcium low sodium diet with successful outcomes.
Each of the subjects ate in random order each of high and low calcium and sodium diets, and total bone mineral balance was measured. The time on each diet was long enough to get reliable data.
Calcium absorbed (leftmost bar (blue) for each diet type) was highest on the two high calcium diets (diet types are along the horizontal axis). Loss of calcium in stool and urine (second and third bars from the left (red and gray, respectively) over each diet type) were lowered by low sodium diet (second group of bars from the left over the ‘CA HIGH NA LOW’ caption), and that was the only diet that produced positive balance – black bar above the horizontal dashed line.
Of interest, the high diet calcium was not achieved entirely with foods. Supplemental calcium was used, eaten during the course of the meals. This means for those who cannot get in enough calcium from food it is not unreasonable to use supplements, but they must be taken directly with the meals, not in between or fasting.
Also note that high calcium with high sodium (first block of four bars) did not achieve positive bone balance, so it is not enough to just add calcium. One needs the two diet factors together. This is what the US diet plan attempts to accomplish.
Low Refined Sugar
We have no trial, but we do have the striking effect of sugars to produce a transient but lofty spike in urine calcium.
Normal people given 100 gm of glucose or sucrose in water increased their urine calcium – the periods numbered below the horizontal line are 20 minutes each so the increase is rapid.
Patients with IH were higher before and higher after the sugar loads. Their family members were the same, because IH is hereditary.
To date no trial has focused on reduced refined sugar per se, nor will this happen. Trials tend toward monotony, the test of things one by one, and sugar is probably not by itself enough of a factor to alter stone formation. But is has its effects, and there is no reason to provoke spikes of urine calcium loss. They will cause a transient rise in supersaturation. Also, since there is no calcium in the sugar drinks the sudden calcium loss in the urine is probably from bone.
Moderate Protein Intake
The US protein intake recommendations appear to be at the lower end of the commonly mentioned 0.8 – 1 gm/kg/d. In the appendices that quantify intakes values plateau at 0.8 mg/kg/d.
For stone formers, high protein intakes will indeed increase urine calcium, a matter of no dispute.
The blue points on this graph are from selected balance experiments of considerable duration. The red points are from shorter experiments. They are detailed in the original article.
The main point is that as one increments diet protein the protein provokes an acid load via the oxidation of sulfur from methionine and cystine, and thence a change in net acid excretion (NAE). Correlative to that change is an increase in urine calcium.
Some authorities doubt that the acid load per se is essential for the effect. The paired pentagons are from a single but well done experiment in which protein was given with and without sufficient alkali to abolish the acid load yet both protein feedings equally raised urine calcium. Even so, urine calcium rises with protein loads and higher urine calcium can raise stone risk.
Some important authorities have maintained that the acid load from protein adversely affects bone, whereas others of equal calibre deny this. Rather than pursue the debate here, I refer those interested to the linked primary article on this site.
The US diet proposes large amounts of fruits and vegetables that provide more alkali than we presently get, and that alkali may well offset the acid load from protein. Likewise, the diet asks for moderation of diet protein, so the urine calcium effects will be correspondingly moderated.
Urine citrate responds to net acid base balance, and if the moderated protein intake is combined with high organic anion intake from fruits and vegetables urine citrate may well rise. The US proposed diet aims toward a potassium intake of about 112 mEq/d mainly from fruits and vegetables.
These food sources will provide the potassium mainly associated with organic anions that include citrate and, like citrate, are metabolized. Being metabolized in their acid forms,their metabolism produces alkali in the form of bicarbonate will signal the renal citrate transporter to permit more citrate to enter the urine. In other words, the foods will act exactly like potassium citrate given as a medication.
Since our current US potassium intake approximates 60 mEq/d the diet will add about 60 mEq more, or the equivalent of six 10 mEq potassium citrate pills. It is precisely this food phenomenon that is exploited in the common idea of drinking lemonade. But lemonade like all fruit juices can be a source of refined sugars depending on the brand, and lemons vary considerably in citrate content. Likewise lemonade becomes monotonous. An altered diet seems far better,
It is possible that the new US diet guidelines, if enacted, will greatly reduce the need for medicinal potassium citrate, with a corresponding fall in cost and unpleasantness of taking the large pills. Although a trial of such a diet for urine citrate increase, would be desirable, it may never take place there being no obvious financial incentives.
When Should Stone Formers Start the Diet?
The Diet is Recommended for Everyone
At the first stone, of course, as it has general health benefits as well as specific and well supported special kidney stone prevention benefits.
More Stones Predicts Poorer Treatment Response
Another reason is that fragmentary data I have gleaned from the many stone trials suggest that waiting may not be an ideal strategy.
On the vertical axis are the percent relapse rates for the treated arms of the trials, plotted against the average number of pre-treatment stones. The names of the trials correspond to references in the detailed article this figure arises in, which is linked below.
Treated ingle stone formers had an about 10 – 12% relapse rate, ‘Mulit’ refers to my published treatment data that used multiple treatments at once. At best my estimates of pretreatment stone averages are coarse because of limited information in the original studies, so the points may well distribute differently. But the general impression will not likely change with details: More stones seems related to higher relapse despite treatment. The other two ‘Multi’ points are accurate, as is the NaKCit point – details were in the paper.
How Should Stone Formers Pursue the Diet?
Like everyone else in the US, of course. The government website is rich in food portion data and advice about diet change. Our patients can enter it with other Americans and essentially swim with the current.
But stones are a disease we want to treat so it is up to us and those who work with us to help. Jill Harris has already written about this matter, and we hope many more stone experts will begin to consider the reality of how to use the diet effectively.
54 Responses to “THE SCIENCE OF THE KIDNEY STONE DIET”
Question on carbs from breads/crackers/pretzels/cereals. Even though they have a low amount of added sugars per the labels do they raise urine calcium or stone risk if I’m keeping in the proper range of added sugars? I eat the lower sodium varieties but I do have a lot of carbs a day from these and wonder if these simple white carbs are okay as long as the added sugars don’t go over the allowable amount.
Fredric L Coe, MD
Hi Geo, Only refined sugar has been proven to raise urine calcium. Starches indeed digest to glucose, but the pace is slow compared to sugar itself. In general starches do not correlate with stone disease except, of course, via obesity which is a stone risk factor. Regards, Fred Coe
Practical question. Suppose I am eating a meal that I know contains, say, 100 mg of oxalic acid. I consume sugar-free (stevia-extract sweetened) lemonade before, during, and after the meal, total about 750 ml of lemonade corresponding to that meal. Also I eat a 250 mg calcium supplement with the food. The supplement is advertised as “bio-available” 250 mg calcium citrate with a proportional amount of magnesium (125 mg) per tablet.
Now, how much of that 100 mg of oxalate in my food is “canceled” by the lemonade and calcium supplement? By that I mean, how much have I reduced the oxalate impact on my kidneys?
I have been doing this for every meal for the past couple of months since my surgery. I’ve been making a lot of stevia-sweetened lemonade, and not yet tired of it; I drink up to 2 liters of it most days, plus other fluids. I take one of the 250 mg calcium tablets with each meal (even the low-oxalate meals), and end up eating 3 or 4 of them a day, in addition to whatever calcium may be naturally in the food. I have wondered how much benefit I’m getting form the lemonade and calcium supplement in terms of reduction of oxalate impact on my kidneys.
Calcium supplements when taken in excess can increase your risk of stones- you only need 1000 mg/day. You would need an urine collection to see where your oxalate levels are. We cannot give you a one to one ratio on calcium and oxalate as everyone absorbs foods and pills differently. I tell my patients to stay to 100 mg/ox a day and get your calcium needs met by food and drink.
I have a family history of ulcers. Taken in calcium gives me extreme pain sometimes,
So your calcium intake increases my stomach
Pains so your diet does not help me it just adds to my pain.
Fredric L Coe, MD
Hi William, Usually high calcium foods like milk soothe ulcers. Calcium supplements are antacids and used for ulcer. So I am surprised that calcium sources worsen things. Perhaps your personal physician can help with this apparent anomaly. Regards, Fred Coe
Dr. Caryl Murchison
Is she taking Calcium citrate??? That could irritate her stomach but Calcium carbonate (Tums) not likely too as you point out, Dr. Coe. I was taking Ca citrate because the calcium is better absorbed as a supplement , but had pyrosis from it. When I switched to Tums ( calcium carbonate) my stomach distress resolved.
Is there a simplified summary of what to do, i.e which Potassium Citrate to buy and how much and the diet? This is very academic 🙂
May I suggest The Kidney Stone Prevention Course. I bring all this information together in a set of videos of education and also offer one month of Q and A group calls to answer your specific questions. It has helped many stone sufferers really understand how to lower kidney stone risk. Find the link here: kidneystonediet.com
My urologist surmises that my five kidney stones episodes over 30 years are uric due to my very recent 24-hour Litholink report of 5.57 24 hour urine pH, 35 year experience of ileostomy/colectomy, and low (1.71 liter) volume.
My urine citrate level was 26 mg/day. I am an otherwise healthy 75 year old male.
Currently prescribed daily are .4mg Tamulosin, 100mg allopurinol, sodium bicarbonate 1300mg, and Theralith XR (pyridoxine hydrochloride 30mg and potassium citrate 400mg daily. I also take both Vitamin D and B12 daily and pantoprazole 20 mg, the latter for nearly 30 years. I follow a very low meat – high vegetable diet and drink 50 – 60 ounces of water daily.
Does this make sense, particularly the Theralogix product?
Fredric L Coe, MD
Hi David, Ileostomy with uric acid stones will not yield to diet – it requires sufficient alkali to raise urine pH well above 6. Because ileostomy losses are sodium alkali the ideal supplement is oral sodium bicarbonate but the dose needs to be a lot higher- 40-60 mEq/day usually. Two OTC sodium bicarbonate tablets, 10 grain size, provide about 12 mEq so 2 tablets 4 to 5 times a day are usually required. You can get urine pH test paper and determine your progress but do a 24 hour urine when you think things are right to get the day average. The allopurinol will not benefit uric acid stones in this setting, the Theralith is futile. The low meat diet unnecessary for the uric acid stones. Regards, Fred Coe
I appreciate your efforts to educate kidney stone patients with evidence-based data.
I have the following questions:
1. Does the recommendation for 1000 to 1,200 mg of diet calcium daily include calcium supplement tablets?
2. Are calcium citrate tablets the best choice for supplemental calcium?
3. How much supplemental calcium citrate can be taken daily without causing more harm than good?
4. Should supplemental calcium intake be monitored with blood and/or urine calcium tests?
Fredric L Coe
Hi Lee, It can, but food sources are probably superior: slow release, taste better. If you use calcium supplements always take them with your larger meals – slower absorption, nutrient to be sure your bones are interested in the calcium (I suspect this matters, not studied it), and will lower oxalate absorption from food – a lot. Calcium citrate may be better – less urine pH rise than from carbonate, but no data I have seen. The daily intake of 1000 to 1200 is ideal, so one uses supplements to supplement what food provides. Since you are a stone former 24 hour urines are needed before prevention, to guide it, and over the years to be sure you know what is happening. So if you add calcium, measure – of course. Regards, Fred Coe
Hi Dr. Coe:
I am confused myself too. My diet included sliced muzzarella and sweets, I am not going to lie to you. I need to replace all those since I cut them off completely last week when I ended up at the emergency room in terrible pain.
I need something as a snack that can replace all this, also what kind of breads I can have.
I don’t have insurance or primary doc, so your help here will be much appreciated.
Thanks a lot!!@
Fredric L Coe
Hi Sylvia, this is in answer to both questions. The diet you need is this one. Sugar is hard to stop, and I had my own problems stopping it. But no one needs it, so you can feel perfectly safe is just letting it go. Since money is a problem right now your best bet is to follow the kidney stone diet, drink a lot, and try to get insured so you can have a physician to guide your care. Regards, Fred Coe
My urologist says I have a lot of stones, how can I find out what kind of stones I have?
I have had 2 extreme painful episodes, but to my knowledge no stone appeared.
In the meantime should I follow your diet plan?
Thank you most sincerely!
Fredric L Coe
Hi Jacqueline, Your urologist can at least exclude uric acid stones from the HU of radiographic density. I presume the stones are calcium based.The diet plan is for people who have been fully evaluated for all causes of stones, so be sure and do this. If you have ‘idiopathic’ calcium stones, treatment does best begin with diet, and if that is not enough meds are added to the diet. Regards, Fred Coe
Anne L. Danahy
Thank you so much for your articles and advice. As a result, I am able to have intellingent conversations with my doctors and come up with a mutually satisfactory treatment plan. My nephrologit refers to you as “my doctor in Chicago”.
We agreed that I will follow the diet recommended here and in 2 months have another 24 hour urine test.
Martin Eugene Murphy
I have a lot of kidney stones that measure 2mm or less, already passing some larger more painful 4mm. I come from an organic farm where we eat a lot of spinach, potatoes, and nuts that are high in oxalates.
I have changed my diet and eat more citrus such as oranges, lemon in my water, etc. and found that it has helped reduce my stones (after my last CT scan) and now I have a much better urine flow.
It would be to our benefit to keep the food oxalate chart in the kitchen to remind us of what works and what is bad for us.
Fredric Coe, MD
Hi Martin, Assume nothing. Get the stones analysed and be sure they are calcium oxalate. Get 24 hour urine testing and fasting morning bloods to be sure you know what is causing stones. Changing diet without testing is never a good idea. Regards, Fred Coe
Is there any negative effect from Vitamin K 2, or K 1 taken for Bone health, and Calcium stone formation?
Fredric Coe, MD
Hi Howiem, I know of no studies about this. SOrry, Fred Coe
I have 2 kidney stones,6 and 7 mm size and despite medicines prescribed by the doc, to my misery, after 10 days of treatments i still have the 2 stones placed inthe same place.
Get pain every now and then when i move too much. My question is what should I do now? do I need to operate? Or can I just leave them there and through diet etc it will find its way out? Also, I am still trying to figure out what i cannot eat anymore, come docs told me i have to elimante cheese from my diet. My stones ar Calcium oxalate.
Hope to get an answer fromyou.
Fredric Coe, MD
Hi Reema, I gather the stones are in the ureters and passing, thence the pain. Your urologist has to decide when it is safe to let things pass and when to operate. I would be sure he knows how much pain you are having. As for prevention, take a look here at one of my more favorite articles. Regards, Fred Coe