Remembering Kevin Moore

Do Low-Carb Diets Increase Kidney Stone Risk? Let’s Ask The Low-Carb Experts

People have all sorts of ideas about low-carb diets based on what they’ve heard somewhere or just on what they think they know about them. It’s why concepts like “artery-clogging” saturated fats still pervade our culture despite all the scientific evidence to the contrary. It doesn’t help that these myths surrounding healthy carbohydrate-restricted diets are perpetuated on a daily basis by so many so-called health “experts” in both the medical and nutrition fields and the general public is none-the-wiser to contradict any of it since they are merely living their lives and trusting the sources of information they are paying attention to. It’s what makes the idea of creating a cultural shift in thinking in favor of low-carb living that much more difficult–but it won’t deter me or the many others who are out here fighting the good fight to educate, encourage and inspire others to give livin’ la vida low-carb a try for themselves.

I literally receive hundreds upon hundreds of e-mails daily from readers who are searching for answers to their questions about their low-carb lifestyle, help with weight loss, or managing some chronic disease they are dealing with. Although I’m not a doctor or nutritionist, I’m always happy to share from my own experiences to see if that information can be beneficial to the person who wrote to me. It’s my pleasure to hear from readers and to offer up assistance in any way that I can. However, from time to time I’ll receive an e-mail from a reader who has an interesting question that is beyond my scope of full understanding enough to share a detailed explanation of what’s possibly going on. It’s okay that I don’t know everything there is to know about nutrition and it’s relationship to being healthy. The good news is I have a TON of connections with people who do. And I decided to tap into that resource again this week to answer a question that came from my fellow health blogger Kelly The Kitchen Kop.

She said she was working on a blog post about low-carb diets and their relationship to kidney stones after becoming concerned when she read a column by Perfect Health Diet author Paul Jaminet entitled “Dangers of Zero-Carb Diets, IV: Kidney Stones” where he argues that people consuming a ketogenic low-carb diet (less than 50g daily) are 500 times more likely to develop kidney stones comprise of uric acid and 50 times more likely to have the more common calcium oxalate kidney stones occur. You’ll recall I just had Paul Jaminet on my podcast last week where we talked about his aversion to people being in a ketogenic state which is why he recommends consuming white rice and potatoes to keep carbohydrate levels lowered but non-ketogenic. It seems Paul is of the opinion that uric acid development is much higher in people who eat a low-carb diet which is one of the culprits in kidney stones and is also a leading contributor to the development of gout (I’ve addressed the gout issue previously in this post).

Of course, he’s referring to people on a “zero-carb diet” in his post and notes that carbohydrate calories should be 20% of total energy consumption. For some low-carbers, they’re already there. But does that mean those of us who for whatever reason choose to consume a more ketogenic level of carbohydrates are putting ourselves at risk for getting kidney stones? I didn’t know the answer, so I decided to throw this one to my expert friends in the low-carb research and medical community for some assistance in answering it. For the record, I’ve never had a kidney stone in my life and I’ve been eating high-fat, moderate protein, ketogenic low-carb for over seven years and counting. Could this be an issue that is less about your nutrition and more about genetic predisposition? Let’s find out!

Dr. William Davis, MD, cardiologist and health blogger at the “Heart Scan Blog”

I believe we know several things with confidence:

1) High animal protein intake increases urinary calcium loss
2) High animal protein intake decrease urinary pH (more acidic)
3) High animal protein intake decrease urinary citrate levels
4) High animal protein intake increases urinary urate

On the other hand, reduced carbohydrates reduces urinary calcium. Weight loss exerts multiple beneficial effects that decrease likelihood of urinary stone formation.

To my knowledge, there have only been studies looking at serum and urinary measures (e.g., oxalate, calcium, pH, etc.) that may be associated with stone formation, but there has not been a prospective study in humans that applies a low-carbohydrate diet versus conventional diet and observes the occurrence of stones.

So the bulk of observations on urine composition on low-carb diets suggests increased potential for urinary stone formation.

That said, it is also important to know that, as you know, “low-carb” comes in many flavors and can vary with regards to green vegetable composition, oxalate content, acid-base effects, etc. There are other factors that can also influence the tendency towards stone formation, such as vitamin D status, urinary magnesium excretion, hydration status (very important), dietary potassium content, etc.

All in all, low-carb likely increases likelihood of stone formation in those susceptible to the effect. However, there are a number of strategies to consider to mitigate the risk, such as vigorous hydration, balancing protein intake with generous green vegetable intake, magnesium and potassium supplementation, vit B6 supplementation. I advise some patients to monitor urinary pH and try to trend towards maintaining an alkaline pH (i.e., greater than 7.0).

Urinary stone formation is a complex topic with vigorous debate on just how important dietary content really is.

Dr. William Yancy, MD, researcher at Duke University and Veterans Administration Medical Center

There is only one article with empirical evidence on this and it only looked at precursors to stone formation. The study was published in the January 2, 2002 issue of American Journal of Kidney Disease called “Effect of low-carbohydrate high-protein diets on acid-base balance, stone-forming propensity, and calcium metabolism.”

Dr. Barry Groves, PhD, “Second Opinions” blogger and author of Trick and Treat

Yes, is the short answer. We have known that eating refined carbs lead to kidney stones for over 30 years, and that reducing carb intake is beneficial. Read my short article about this called “Kidney Stones and Kidney Failure Information” for more information.

Jacqueline Eberstein, RN, “Controlled Carbohydrate Nutrition” owner who worked with Dr. Atkins for 30 years

Over the years working with Bob Atkins we saw people with kidney stones. Most people had a history of past stone formation. Once one has had a stone more can follow. The most common stone being calcium oxalate. I don’t believe that doing low carb itself causes stones although obesity and metabolic syndrome can be contributing factors. Drinking large quantities of phosphates in soda also can be problematic. Interesting to note that in the last 30 years the incidence of stone formation is increasing as is obesity and metabolic syndrome. In patients with a history of stones we supplemented with magnesium as many of us are too low in magnesium and this can contribute to stone formation.

One of the most important factors in preventing stone re-occurrence is adequate hydration. This is especially important in the early stages of carb restriction when there can be a strong diuretic effect. Also people on diuretics are more prone to stone formation. The biggest caution I can give is stay hydrated especially if you have a history of kidney stones yourself or a family history.

Dr. Richard Johnson, MD, renal disease specialist at the University of Colorado-Denver

There is increasing evidence that soft drink intake is associated with kidney stones, and it has been linked with fructose intake. We have unpublished data that fructose intake results in a fall in urinary citrate, which is an inhibitor of stones. Thus, the decrease in urinary citrate could predispose those who drink soft drinks to develop kidney stones.

Dr. Stephen Phinney, PhD, noted low-carb researcher and co-author of The New Atkins For A New You

I need to point out that the cause of kidney stones is about where astronomy was before Johannes Kepler, but because kidney stones hurt like hell and people experiencing that much pain really, really want something (or someone) to blame. That said, here are some points to ponder:

• Nephrolithiasis runs in families, but we do not know what (or how many) genes are involved.
• People with metabolic syndrome or type-2 diabetes are more likely to develop kidney stones, but again we are a bit short on understanding the connection.
• Most kidney stones are made of calcium combined with either phosphate or oxalate, and after that come stones formed from urate (aka uric acid).
• When humans go on a ketogenic diet, their blood levels of uric acid go up for a period of 4-8 weeks, after which they come back down (even if they strictly adhere to the same level of carb restriction).
• This early effect of carb restriction has led some clinicians (I’m purposely withholding the word ‘scientist’ here) to suggest that low carb diets cause uric acid stones. Mechanistically, however, the rise in serum uric acid occurs because LESS OF IT is getting excreted into the urine due to competition with ketones. And obviously, kidney stones form in the fluid that is EXCRETED, not from what’s in the blood.
• Because low carb diets deliver superior results in the face of insulin resistance, people with metabolic syndrome or Type 2 diabetes tend to gravitate to this dietary treatment, which means that ‘stone-formers’ are attracted to carbohydrate restriction. Thus doctors may see a trend of more people with kidney stones who are on low carb diets, despite there being no causal link. (Gary Taubes waxes eloquently about this failure of epidemiology in Good Calories Bad Calories).
• High protein diets tend to contain more purines, which are metabolized by humans to uric acid, which in turn increases uric acid excretion and thus stone formation risk. This, among many other reasons, is why we counsel people that low carb diets should not be high protein diets. Around the globe, aboriginal cultures from the Arctic to Africa learned to treasure dietary fat over lean protein.
• A significant contributor to kidney stone formation is dehydration. Here is something that might significantly benefit your readership. When you take away peoples’ soda/pop and fruit juice, they tend to drink less fluid. Add to that the diuretic effect of nutritional ketosis and some people following low carb diets may be prone to being short of fluids much of the time. This is one of many reasons why I’m like a broken record in urging people on low carb diets to add 2 cups of broth/bouillon to their daily intake — not just in the first few weeks of adaptation — but permanently (as long as they stay low carb). And yes, 4-6 glasses of water per day probably also helps.

Be sure to read “An update and practical guide to renal stone management” published in the July 2, 2010 issue of Nephron Clinical Practice for more on this subject.

Now that the low-carb experts have weighed in, what say YOU? Have you ever experienced kidney stones? Did you even think for a moment that it was your low-carb diet that contributed to the development of them or had you been dealing with this issue long before you started livin’ la vida low-carb? Share your experiences with us in the comments section below so we can benefit from your wisdom regarding kidney stones and low-carb diets.

  • How about this: low carb per se doesn’t cause kidney stones; many people’s low carb diets do. Diets of lean chicken, mayonnaise, diet coke, & lettuce and diets of “meat & water” are both much different than traditional low carb diets.

  • About 5 years ago, I did atkins for about 6 months, and then the weekend of our “street festival”, I went off of atkins suddenly and ate 3 days of fair food and soda, with no water intake. I was out in the sun all day getting dehydrated and drinking pop. With fructose in it. I can assure you this will result in kidney stones. I’ve never had them before, and I’ve never had them after.

    • Frank, let me know when you start blogging at that URL…I’ll promote it on my blog.

  • Jimmy, have I mentioned lately that YOU ARE THE BEST?!!!!!!

    Not only do I *not* have to do any more research on this (you know how time-consuming that is), and now I can just link to this post when I get mine up, but ALSO, the info you gathered from all these experts covers the issue SO WELL!!!

    Thank you!!!!!!!

  • I was just diagnosed with gout last week which is related to kidney stones in that it can result from elevated levels of uric acid. Rather than point to the meat in my diet increasing the production of uric acid from purine metabolism, I believe it probably comes from a few factors like:

    1) I wasn’t eating any fruit or taking any supplements which means I was probably very low in vitamin C in my diet. Vitamin C apparently is one of the most effective ways of lowering uric acid levels.

    2) I live in a colder climate in Canada and over the winter I don’t near enough sun to produce the Vitamin D I need. Vitamin D seems to be linked to Gout as well.

    3) I don’t drink a lot of alcohol but will occasionally indulge in a scotch before dinner and a glass or two of wine with dinner. Again alcohol associated with gout.

    4) I tend to go a bit overboard with the processed meat (bacon, sausage) so that could have contributed as well.

    As a result of the diagnosis, I’ve started supplementing with fish oil and a multi vitamin and added in extra Vitamins D and C. I’ve also added some fruit back into my diet (berries only because of their low sugar and high fiber content). In terms of diet, I’ve about doubled my veggie intake, removed for now all processed meat and reduced slightly my other meat intake (to make room on the plate for veggies).

    • You probably were getting too much protein. More fat! Drink cream if you have to.

      The Inuit didn’t have vitamin C or D supplements, and it’s dark a lot of the year up in the frozen north…

  • amanda

    I had several bouts of kidney stones back in the mid-2000s. I was vegan at the time. Since eating paleo(ish) I thankfully haven’t experienced any. I have noticed on days that I don’t drink enough water AND eat an unusually large amount of potassium rich food (say, a soup made with squash and coconut milk followed by some fruit and cream) I will feel like somebody kicked me in the sides of my lower back, which I am assuming is my kidneys telling me to do something different than what I am doing. Drinking lots of water with a small amount of sea salt added seems to help in these instances. Additionally, my mother has been hospitalized at least once a year for as long as I can remember with kidney stones. Since dropping sugar and most refined carbs from her diet she hasn’t had any kidney problems–a trend that will hopefully keep up.

  • Barb in Tennessee

    Jimmy, the year I had a kidney stone that required lithotrypsy, I was consuming 2 liters of Pepsi (not diet) each day. Since i have been on low carb (50g) I have not had any problems with kidney stones. I also take extra vitamin D and Magnesium, which helps keep the calcium where it’s needed. My urologist told me that we can get calcium oxalate from the foods we eat like spinach, black tea, etc. I think that if we take our correct vitamins and minerals and drink plenty of water, kidneys stones should not be a worry on low-carb.

  • At the risk of tempting the fates… Never had a one and even when I wasn’t a low carber; because of my participation in strength athletics, I still consumed what would be considered unusually high amounts of protein and still; not a kidney stone..

  • veggienft

    I’m on a strict paleolithic diet, not necessarily by choice, but out of medical necessity. I don’t eat foods with lectins I’m sensitive to, and I ingest very little (minute) fructose and lactose. Recently I had my first kidney stone. It was EXCRUCIATING. I believe the kidney stone was tied to some new cheap coffee I had drunk for a couple weeks. It turns out that irrational fears of past, relatively safe pesticides has forced food processors to develop cyromazine, a new pesticide. Cyromazine forms melamine in the kidneys. There has been a giant upsurge in melamine kidney stones recently. Reportedly we can remove cyromazine from veggies by soaking. But we can’t soak coffee or tea before ingestion.

    Wheat, rice, corn, sugar, potatoes all reach our plates after having outer shells removed. Lettuce, broccoli, cauliflower, asparagus, coffee, tea? ……have no such protection. It stands to reason low carbers would eat more air-exposure veggies.

    Does a high carb diet protect people from exposure to cyromazine and melamine? If so, would the ill effects of a high carb diet outweigh the ill effects of melamine poisoning? What about the third option? …..OUTLAW CYROMAZINE.

  • veggienft

    Healthy lean people tend to keep doing what they’ve been doing. It’s uncommon to find healthy lean people taking up low carb dieting. It happens. It’s just the exception, not the rule. So tying any ill health issue to low carb diets, shouldn’t ill health first be considered as a cause, not an effect.

  • veggienft

    It seems to me, as the experts have stated, the solution for kidney stones is to not form the solids which compose them. People who don’t form stones don’t have to pass them. The solids for kidney stones are crystalized on kidney surfaces, presumably in the tubules. The solids agglutinate to form stones, and the stones (painfully) travel down the ureters. So, between high-carbers and low-carbers, we’re looking for the people who form kidney stone solids, not necessarily for the people who are passing kidney stones. Are there any clues? Yes. Generally people stop abusing themselves with sugar and wheat, and start low-carbing. The change, as we age, goes from high-carbing to low-carbing. So some evidence indicates that low carbers are more prone to pass kidney stones? Obviously the solids broke loose and formed stones while the hosts were low carbing. But when did the solids form? While low carbing, or more likely, during the previous high carb diet.

  • I’ve never had any problems with kidney stones, but neither has anyone in my family even though they all eat the standard American diet. Even when I ate the standard American diet and drank more diet coke than should be safe for human consumption, I never had any problems. So it’s probably more genetic than diet.

    I’ve been doing very low carb for almost a year now, since May 3rd last year. As for me, I drink a lot (not alcohol if that’s what you’re thinking 😛 ), usually sugar-free kool-aid. I would say in a typical day that I consume a couple or three cans of diet coke (I’ve cut back a lot let me tell you), a couple of homemade Italian-style cappuccinos, and then probably a liter or maybe more of kool-aid. Does my habit for staying well hydrated help me? Maybe? Or I might just be lucky.

  • ReneeAnn

    I tend to get calcium oxalate stones, but I’m very aware of early symptoms of problems (concentrated splattery urine) and haven’t had a stone in two or three years. To achieve this,I drink plenty of water, take calcium oxalate with magnesium oxalate and have to stay on a strict low oxalate diet. I’ve come to a new understanding that leaky gut, which I definitely have, may be the primary cause of my stones. For several months I’ve been eating Paleo, low oxalate and sort of GAPS to heal my gut. I am expecting to be able to eat more oxalate rich foods at some point, but my little tests have shown that I’m not there yet. But, when I started Paleo and dramatically increased my protein, I saw no ill effects regarding stones.

  • Thank you Jimmy for all this research. Like Kelly, I will be able to utilize it most particularly with a new client who has told me he wants me to design a no cholesterol plant based diet. Boy is he in for a big surprise!

  • I had symptoms of a kidney stone last summer during my 9th month of Atkins, modified to be WAPF-friendly (no vegetable oil, artificial sweeteners or soy). I was eating a LOT of fat — at least a half cup of raw cream daily, and 3-5 Tbsp coconut oil. Over the summer, I started using less butter, and had not taken my cod liver oil/butter oil for several months.

    From induction, I had added back dairy, nuts, berries, and was eating veggies. I was really afraid to keep adding back anything with carbs, so I kind of stagnated around 30-35g carbs per day, 60-75% of calories from fat. At that time, I was drinking several shots of decaf espresso per day, and also had eaten chard and spinach for a couple days straight.

    I cut out the espresso and oxalate-laden greens entirely and added back the cod liver oil/butter oil daily, and didn’t have another stone.

    I did stop eating low-carb, though, because I had been suffering from hypothyroid symptoms (hair and eyebrow loss) after about 4 months of the diet (WOL, I mean, LOL) which progressed to severe fatigue, menstrual irregularities, and irritability (all of which had previously disappeared eating a higher-carb WAPF diet). I won’t vilify Dr. Atkins, because he warned against this in his book. I should have steadily added back carbohydrate-rich plant foods like beans and whole grains in the timeline he recommended, at the very least, or cheated more often.