You’re staring at the recycling bin. It’s full. Mostly cans of LaCroix, Polar, or maybe that Topo Chico you’re obsessed with lately. It feels like a healthy win because you aren’t drinking soda anymore. But then, a random comment from a coworker or a terrifying deep-dive on Reddit makes you pause. "Be careful," they say, "that carbonation will give you kidney stones." Suddenly, every little twinge in your lower back feels like a ticking time bomb.
Is seltzer water and kidney stones a real connection, or just another piece of internet wellness lore designed to make us enjoy life less?
The short answer? It’s complicated. But honestly, for most people, the fear is way overblown.
The Chemistry of the Sparkle
Let’s get the science out of the way first. Seltzer is just water infused with carbon dioxide gas under pressure. That process creates carbonic acid. This is why seltzer has a slightly lower pH than flat water. It's more acidic. People hear "acid" and immediately think their insides are dissolving or their kidneys are being pickled.
But your body is a master at maintaining homeostasis. When you drink seltzer, that mild acidity is neutralized by your saliva and the buffering systems in your blood long before it ever reaches your kidneys. The carbonation itself—those bubbles—does not cause stones. It's just gas. You burp it out. It doesn't travel to your renal system and crystallize into jagged little rocks.
Kidney stones, specifically the most common type called calcium oxalate stones, form when your urine becomes too concentrated. Think of it like making rock candy. If you have too much sugar and not enough water, crystals form. In your kidneys, if you have too much calcium, oxalate, or uric acid and not enough liquid to flush them out, you get a stone.
Why Seltzer Gets a Bad Rap
The confusion usually stems from "club soda" or "tonic water," which are not the same thing as plain seltzer. Club soda often has added sodium bicarbonate or potassium sulfate to mimic the taste of natural mineral water. Sodium is a huge trigger for kidney stones. When you eat (or drink) too much salt, your kidneys have to dump more calcium into your urine. More calcium in the urine means a higher chance of it bonding with oxalates to create a stone.
Then there’s the "cola" factor.
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For decades, doctors have warned kidney stone patients to stay away from dark sodas. Those drinks contain phosphoric acid. A study published in the Clinical Journal of the American Society of Nephrology found that sugary soda consumption is significantly linked to a higher risk of stone formation. People often lump all "fizzy drinks" into the same category, but seltzer lacks the phosphoric acid and high-fructose corn syrup that make colas so risky.
The Mineral Water Wildcard
Now, mineral water is a bit of a different beast. Brands like Gerolsteiner or San Pellegrino actually contain minerals like calcium and magnesium.
You might think, "Wait, if the stones are made of calcium, shouldn't I avoid calcium-rich water?"
Actually, no. This is one of the most counterintuitive parts of kidney health. Research, including work from the Harvard T.H. Chan School of Public Health, suggests that dietary calcium—calcium you get from food and water—actually protects you from stones. It binds to oxalates in your stomach and intestines before they ever get to your kidneys. This allows the oxalates to pass through your digestive tract rather than being filtered by the kidneys.
So, drinking mineral-rich bubbly water might actually be better for you than plain filtered water if you're prone to oxalate stones.
When Bubbly Water Becomes a Problem
There are a few scenarios where your seltzer habit might actually be working against you.
First: the flavorings. Many sparkling waters use "natural flavors" or citric acid. While citric acid (citrate) is generally a stone-inhibitor, some flavored waters use additives that might subtly change your urine chemistry. If you're drinking "sparkling lemonade" with 40 grams of sugar, the bubbles aren't the problem—the sugar is. High sugar intake increases calcium excretion.
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Second: the "displacement" effect. Are you drinking seltzer instead of plain water? For most, this is fine. But for some, the carbonation makes them feel full faster. If the bubbles make you stop drinking before you’ve actually hydrated your body, your urine remains concentrated.
Third: there is a very rare condition called Dent’s disease or certain types of renal tubular acidosis where the body’s acid-base balance is precarious. In those specific, medically diagnosed cases, doctors might tell you to stick to flat, pH-neutral water. But if you had this, you’d likely already be under the care of a nephrologist.
Real Experts Weigh In
Dr. Gregory Wigmont, a urologist who has spent years treating stone formers, often tells his patients that the "best" water is the one they will actually drink. Dehydration is the number one cause of stones. Period. If you hate plain tap water and find yourself dehydrated, but you’ll happily crush four cans of seltzer a day, the seltzer is helping you prevent stones by keeping your volume up.
"I see patients who are terrified of the bubbles," Wigmont says. "I tell them to look at the sodium label. If it's zero sodium and zero sugar, I don't care if it's fizzy. Just keep the pipes moving."
A 2021 study looked at the "Net Acid Load" of different beverages. While seltzer is slightly acidic, its impact on urine pH was negligible compared to the massive impact of diet (like eating a lot of animal protein).
How to Spot a "Bad" Seltzer
If you're at the grocery store, do a quick scan. You want to avoid anything where the "Sodium" line says anything other than 0mg or a very low number (like under 20mg).
Avoid "Tonic Water." It’s basically clear soda. It’s loaded with sugar (or high fructose corn syrup) and quinine. Quinine gives it that bitter edge, but the sugar content is identical to a Sprite or a Coke. That will absolutely spike your stone risk.
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Check for "Sweeteners." Even artificial sweeteners like aspartame or sucralose are under scrutiny. While the link to kidney stones isn't definitive, some studies suggest they may affect the gut microbiome and metabolic health, which indirectly influences how your body handles minerals.
The Oxalate Connection
If you are a "chronic stone former," you've probably heard of oxalates. Spinach, beets, almonds, and rhubarb are loaded with them. Some people worry that seltzer somehow interacts with these foods.
There is zero evidence for this.
In fact, if you’re eating a high-oxalate meal, drinking a mineral-rich sparkling water (look for high calcium on the label) could potentially help block the absorption of those oxalates. It’s like a little chemistry experiment happening in your gut.
The Bottom Line on Seltzer Water and Kidney Stones
Most of us aren't drinking enough water. If seltzer makes hydration enjoyable, it is your friend. The "acid" in carbonated water is too weak to cause the bone leaching or kidney issues that myths suggest.
However, if you have a history of calcium phosphate stones (a less common type), your doctor might want you to monitor your urine pH more closely. For everyone else—the calcium oxalate crowd or the "I just don't want a stone" crowd—the bubbles are safe.
Don't let the fear-mongering take away your favorite drink. Just stay away from the sugary stuff and watch the sodium.
Actionable Steps for Kidney Health
- Check the Label: Look for "0mg Sodium" on your seltzer cans. Sodium is the hidden stone-maker, not the carbonation.
- The Lemon Trick: If you're worried about stones, add a squeeze of real lemon to your seltzer. Lemons are high in citrate, which actively prevents crystals from sticking together.
- Target Volume: Aim for enough seltzer (and plain water) to produce about 2.5 liters of urine a day. This is the gold standard for stone prevention.
- Pair with Calcium: If you're eating something high in oxalates (like a spinach salad), drink a mineral water with a high calcium content to bind those oxalates in the gut.
- Avoid Tonics: Switch from tonic water to plain seltzer or "sparkling mineral water" to cut out unnecessary sugars that stress the kidneys.
- Monitor Your Urine: If it's pale yellow, you're doing great. If it's dark like apple juice, drink another seltzer immediately, bubbles and all.
The fear surrounding seltzer water and kidney stones is largely a misunderstanding of how the body handles CO2. Drink up, stay hydrated, and keep those kidneys flushing.