Plain seltzer water is not bad for you. It hydrates just as well as still water, doesn’t damage your bones, and poses only minimal risk to your teeth. The concerns people have about carbonated water mostly stem from research on sugary sodas and flavored soft drinks, which behave very differently in your body than plain carbonated water does.
That said, carbonation isn’t completely neutral. There are a few real effects worth understanding, especially if you drink seltzer all day or prefer flavored varieties.
The Tooth Enamel Question
This is the concern with the most truth behind it, though the risk is smaller than most people assume. When carbon dioxide dissolves in water, it forms carbonic acid, which lowers the pH. Enamel begins to dissolve at a pH of 5.5, and some carbonated waters do dip below that threshold. A review of 105 bottled waters, including 32 carbonated varieties, found that several fell below the safe pH level for teeth.
But context matters. Carbonic acid is a weak acid, and the exposure time from drinking a glass of seltzer is brief. The real damage seen in studies comes from soft drinks that combine carbonation with citric acid, phosphoric acid, or tartaric acid. Those drinks can push pH levels as low as 2.5. Teeth soaked in those beverages in lab settings lost measurable mineral weight. Plain seltzer, without those added acids, is far less erosive.
Flavored seltzers land somewhere in between. Many brands add citric acid for tartness, which drops the pH closer to that 5.5 danger zone. If you drink flavored seltzer throughout the day, sipping it slowly and bathing your teeth in mild acid for hours, that’s a meaningfully different exposure than finishing a glass with a meal. Drinking through a straw, rinsing with plain water afterward, or choosing unflavored varieties all reduce whatever small risk exists.
Hydration Is Identical to Still Water
One common worry is that carbonation somehow makes water less hydrating. It doesn’t. A study using the beverage hydration index, which measures how much urine your body produces after drinking specific beverages and compares them to plain water, found that sparkling water scored identically to regular water. Your body absorbs the fluid the same way regardless of whether it contains dissolved carbon dioxide. If you find it easier to drink enough water when it’s fizzy, seltzer is a perfectly effective way to stay hydrated.
Bone Density and the Soda Confusion
The idea that carbonated drinks weaken bones comes from research on cola, not carbonated water. Cola contains phosphoric acid, which at high intakes can shift your body’s calcium-to-phosphorus ratio, potentially triggering a hormonal response that pulls calcium from bones. High phosphorus combined with low calcium intake can stimulate parathyroid hormone, promote bone loss, and even reduce the activation of vitamin D. Sugar and sodium in soft drinks can also increase calcium loss through urine.
None of this applies to plain seltzer. It contains no phosphoric acid, no sugar, and no sodium. (Club soda does contain about 3% of your daily sodium value per serving, so it’s worth noting the distinction: seltzer is just water plus CO2, while club soda has added minerals.) There is no clinical evidence that the carbonation itself, the dissolved carbon dioxide, has any negative effect on bone mineral density.
Digestive Effects: Bloating but Not Harm
Carbonated water introduces gas into your stomach, and that gas has to go somewhere. For most people, this means occasional burping or a temporary feeling of fullness. A study on healthy volunteers found that carbonated water didn’t change how quickly food left the stomach overall, but it did change where food sat during digestion. With carbonated water, a significantly greater proportion of both solids and liquids remained in the upper stomach compared to still water (74% vs. 56% for solids, 43% vs. 27% for liquids). This redistribution is likely caused by the gas distending the upper stomach.
For people with irritable bowel syndrome or chronic bloating, that extra distension can amplify discomfort. If carbonated water consistently makes you feel bloated or gassy, that’s your body telling you something useful, even though it’s not causing any structural damage. People without digestive sensitivities generally tolerate it without issues.
Can Seltzer Make You Hungrier?
One animal study found that rats given carbonated beverages over roughly a year gained weight faster than rats drinking flat versions of the same beverage or tap water. The mechanism: carbonation triggered higher levels of ghrelin, the hormone that signals hunger, which led the rats to eat more. Their livers also accumulated more fat. A parallel experiment with 20 healthy men showed ghrelin levels rose after drinking carbonated beverages compared to flat ones.
This is a single study, and the effect in humans was measured only as a short-term hormonal spike, not long-term weight gain. It’s not enough evidence to say seltzer causes obesity. But if you notice you tend to snack more when drinking seltzer, this hormonal response could be part of the explanation.
Kidney Stones and Mineral Content
The relationship between sparkling water and kidney stones depends almost entirely on what minerals are dissolved in the water, not on the carbonation itself. A comparison of 126 sparkling water brands across Europe found wide variation in calcium, sodium, and bicarbonate levels. Water with very high calcium content (above 232 mg per liter) has been linked to excess calcium in urine, a risk factor for calcium stones. High sodium intake also promotes stone formation by increasing urinary calcium excretion.
On the other hand, sparkling waters high in bicarbonate may actually help prevent stones. Bicarbonate raises urinary pH, reducing the risk of uric acid crystals forming, and promotes excretion of stone-inhibiting compounds like magnesium and citrate. Research suggests that the high bicarbonate in some mineral waters can offset the effect of their calcium content. The takeaway for people concerned about kidney stones: check your brand’s mineral label rather than avoiding carbonated water as a category.
Plain vs. Flavored: A Real Distinction
The single most important detail in this entire topic is the difference between plain seltzer and everything else. Plain seltzer is water with carbon dioxide and nothing else. Flavored seltzers frequently contain citric acid, which significantly increases acidity and erosive potential. Tonic water contains sugar. Club soda contains added sodium. Each of those additions changes the health profile in ways that plain carbonation alone does not.
If you’re drinking plain seltzer as a replacement for still water, you’re making a nutritionally equivalent choice with a slightly higher (but still low) risk to tooth enamel. If you’re drinking it instead of soda, juice, or sweetened beverages, you’re making a clear upgrade. The carbonation itself is close to harmless for most people. What’s mixed in with it is what matters.