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BackTable / Urology / Article
Sodium & Stone Formation: A Fluid Approach to Kidney Stone Prevention
Olivia Reid • Oct 28, 2023 • 37 hits
Dr. Kristina Penniston, expert clinical dietician, and Dr. Manoj Monga, renowned urologist, speak on the importance of fluids, including the different types available, and sodium restriction as pivotal components of kidney stone prevention.
Dr. Penniston highlights the personalized nature of fluid intake, even when 24-hour urine data is unavailable. She explains a strategy that entails tailored guidance based on individual factors, such as body size, surface area, and activity levels. Delving into the topic of water types, dispelling myths and misconceptions, Dr. Penniston emphasizes that while hard water, rich in minerals, may have preventive benefits, its effectiveness depends on stone type. She reassures readers that concerns about sodium in soft water are largely unfounded, and the impact of alkaline water varies based on its composition. Furthermore, Dr. Penniston speaks on the role of sodium in stone formation, advocating for a more nuanced approach than a strict 1500-milligram target. She relays that sodium restriction's priority depends on individual factors, such as the presence of hypercalciuria.
This article features excerpts from the BackTable Urology Podcast. We've provided the highlight reel in this article, and you can listen to the full podcast below.
The BackTable Urology Brief
• The individualized approach to fluid intake for kidney stone prevention considers factors like body size, activity levels, and stone type.
• Dr. Penniston speaks on the role of water types in kidney stone formation, clarifying the potential benefits of hard water, the negligible sodium content in soft water, and the variable impact of alkaline water.
• The recommended sodium intake in kidney stone prevention can differ from a strict 1500 milligram target. Dr. Penniston stresses the individualized nature of sodium management, considering hypercalciuria and patient-specific factors.
Table of Contents
(1) Precision Fluid Management in Kidney Stone Prevention
(2) Water Types & Kidney Stones
(3) Sodium Restriction in Kidney Stone Prevention: Examining the 1500 Milligram Target
Precision Fluid Management in Kidney Stone Prevention
Dr. Penniston delves into the intricacies of fluid intake as a crucial element in preventing kidney stones, shedding light on her personalized approach. Emphasizing how each patient requires a tailored target, Dr. Penniston explains the comprehensive diet assessment that she uses to extract vital information. There is no one-size-fits-all solution for fluid intake because various factors come into play, such as body size, surface area, and activity level. While the general rule is that producing two liters of urine often necessitates drinking at least three liters of fluids, this can be further customized for individual patients. Furthermore, Dr. Penniston discusses the choice of fluids, addressing the common misconception that water is the only suitable option. She explores various strategies to make fluid intake more manageable, from flavoring water with fruit or vegetables to using creative reminders for timely consumption.
[Dr. Manoj Monga]
Is it one-size-fits-all for fluid intake, or what do you set as the target for each patient?
[Dr. Kristina Penniston]
You asked about empiric suggestions, like if a patient doesn't do a 24-hour urine. My answer to that was, I'll do a diet assessment because I still want to be targeted. I still want to provide some sort of personalized approach rather than saying, "Here's eight things that most people do. I'm not sure any one of them might work for you, but do them all." Even in the absence of 24-hour urine, I believe I can elicit information that will help me target my directions.
Let's say fluids is one. Let's say I know from their diet assessment that they don't drink very much because I'll ask people to tell me what they drink in a day, and we'll work together and figure out the ounces that that is. I'll show them a typical glass or something, and they'll tell me about that. Or if I have the urine collection and it shows volume under two liters, then I will say, "We need to increase your fluid intake."
I don't think there's a one-size-fits-all approach to everyone. People are of different body sizes, that means they have different body surface areas and that means that a larger person is going to lose more fluids through their skin than a smaller person. People have different consistency of their bowel movements; some are more watery than others. We exhale water, so not all of the things we drink go right through our kidneys.
I'll somewhat target the fluid intake to the size of the person, but in general, we know that in order to produce, let's say at least two liters of urine, one has to usually drink at least three liters of fluids. I'll target that as a good goal or if I want the patient to produce more urine, I might go higher. If the patient is a very aggressive athlete, I can presume that they would sweat a lot, they'll need to replace even more.
Then as far as particular fluids, I think a lot of patients feel like we are only talking about water. I have a lot of patients who don't like water or who can't drink the water at their homes because of contamination or they have well water that they don't drink or something. I think it's important for us, not only to help people identify the amount of fluids they should drink, but also which fluids. I think we can be generous and very broad and tell patients basically all fluids count. Of course, we want you to drink as many low-sugar, low-calorie, low-alcohol beverages as possible, but there's even room for those things as well.
I've worked with patients to figure out ways to flavor their waters with fruit or vegetables or to use water alternatives. I work a lot with patients on scheduling their fluid intake. A lot of people don't seem to respond to thirst. Sometimes it requires using your cell phone to beep at you every couple of hours to drink, or I do some techniques like give people rubber bands to wear around their wrist, five rubber bands, and then I'll give them a water bottle, and I'll say, "Every time you finish one of these, take off a rubber band, and by the end of the day they should all be gone or you know, you still have some drinking to do." I think there's a lot of ways we can be creative about fluids and very targeted.
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Water Types & Kidney Stones
Dr. Monga and Dr. Penniston dive into the question of whether the type of water consumed holds significance in the context of kidney stone prevention. Dr. Penniston provides valuable insights, asserting that, in general, the type of water plays a relatively minor role. She discourages the notion of a "best water" and steers clear of magical thinking regarding water choices.
While all water sources contribute to urine output, Dr. Penniston does highlight that hard water, known for its mineral content, particularly magnesium, can have potential preventive benefits against kidney stones. However, she emphasizes that its effectiveness might hinge on the specific type of stones the patient is prone to form. The topic of soft water, often a source of concern due to potential sodium chloride content, is also addressed. Dr. Penniston reveals that the sodium content in most cases is relatively low, debunking misconceptions. Alkaline water is another aspect, with its impact contingent on how it's made alkaline. Water enhanced with sodium bicarbonate or similar bicarbonate compounds can be advantageous for patients aiming to augment their alkaline dietary load and reduce renal acid load. However, not all alkaline waters offer the same benefits, as it hinges on their composition.
[Dr. Manoj Monga]
Hard water, soft water, alkaline water: Is the type of water important?
[Dr. Kristina Penniston]
In general, I would say no. All waters are fluids, and they will all contribute to urine output. I think if I reframe the question a little bit, patients always want to know, "What's the best water?" Magical thinking like, "What's the best thing I should drink?" I always say, "All of them." There is evidence that hard water, because of the minerals that it contains, oftentimes magnesium is one of those, actually can prevent kidney stones. I'm not sure that it alone can do so. Of course, it would depend on the type of stone the patient was forming. I think there's benefits of hard water.
There's concern about soft water because it might contain sodium chloride. Well, it’s not really as much as people have thought or people think. There's evidence, people have looked at it and measured it, and there's a very small amount of sodium in soft water, in most cases. Then alkaline waters, it depends on how the water is made alkaline. If the water has been made alkaline because of the addition of sodium bicarbonate or some other bicarbonate or bicarbonate precursor, then that could be very beneficial for patients who need to increase their alkaline load of their diet and the alkaline load that the kidneys experience. Other waters that are made of alkaline pH but they don't have those ingredients in them aren’t going to do anything, they're not magical, they're not special in any way.
Sodium Restriction in Kidney Stone Prevention: Examining the 1500 Milligram Target
Dr. Penniston provides valuable insights into the controversy of sodium consumption, highlighting that 1500 milligrams is a rather low figure, referencing the general recommendations, which hover around 2,300 to 2,400 milligrams of sodium per day, as advocated by the USDA and various authoritative bodies. Dr. Penniston delves into the scientific literature, revealing that some studies suggest no additional benefits to further reducing sodium intake, but this outcome can vary depending on the specific study's focus and measurements. As previously mentioned, Dr. Penniston's approach is inherently individualized, as she recognizes that sodium, particularly in the form of sodium chloride, can potentially induce hypercalciuria due to the expansion of extracellular volume it causes. However, not every patient exhibits hypercalciuria, and its significance as a dietary recommendation depends on individual patient factors. While sodium restriction is generally advisable, it may not be the top priority for every kidney stone patient.
[Dr. Manoj Monga]
For sodium, is 1500 milligrams your target?
[Dr. Kristina Penniston]
That's pretty low. The general ballpark milligrams per day that is recommended by the USDA and other authorities is generally 2,300 to 2,400 milligrams of sodium. 1,500 is often touted for congestive heart failure. There are some studies, if you look in the literature, that suggest that there are no added benefits to eating that little sodium. Now, it depends on the study's outcomes and what they were looking at and what they were measuring, but I don't think people have to be quite that restrictive. I think that we can, again, take this somewhat individually.
The main concern with sodium, in the form of sodium chloride in particular, is that it may induce hypercalciuria because of the expansion of extracellular volume that it creates, but not every patient has hypercalciuria. Even patients with high salt intakes, I might not place that as a high priority on their diet recommendations unless they also have hypercalciuria. Yes, I think most people need to restrict their salt, and I work with a lot of patients to do that, but it's not always the number one priority for everyone.
Podcast Contributors
Dr. Kristina Penniston
Dr. Kristina Penniston is a clinical nutritionist specializing in therapy for patients with urologic diseases.
Dr. Manoj Monga
Dr. Manoj Monga is the chair of the urology department at UC San Diego in California.
Cite This Podcast
BackTable, LLC (Producer). (2023, June 28). Ep. 104 – Dietary Modifications for Kidney Stone Prevention [Audio podcast]. Retrieved from https://www.backtable.com
Disclaimer: The Materials available on BackTable.com are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients. The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.
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