Plain seltzer water is not bad for you in any meaningful way. It hydrates just as well as still water, doesn’t weaken your bones, and contains zero sugar or calories. But the full picture has some nuances worth knowing, especially when it comes to your teeth, your digestion, and flavored varieties that behave differently than the plain stuff.
Your Teeth Are the Main Concern
When carbon dioxide dissolves in water, it forms a weak acid called carbonic acid. This lowers the pH of seltzer compared to flat water, making it slightly more acidic. The American Dental Association considers plain sparkling water safe in moderation, noting it causes only minimal enamel erosion compared to sodas and sports drinks. The real issue isn’t the occasional glass with dinner. It’s the habit of sipping seltzer slowly throughout the entire day, which bathes your teeth in that mildly acidic environment for hours.
Flavored seltzers are a different story. Citrus-flavored varieties often contain added citric acid, which drops the pH further and meaningfully increases the erosive potential. If you drink flavored seltzer regularly, the ADA recommends having it in one sitting or alongside a meal rather than nursing a can over several hours. Drinking it with food stimulates saliva production, which helps neutralize the acid faster. Replacing fluoridated tap water entirely with seltzer is also worth avoiding, since you’d lose the protective benefits fluoride provides to enamel.
Bloating and Acid Reflux
Carbonation introduces gas into your digestive system, which can cause bloating, burping, and a feeling of fullness. For most people this is temporary and harmless, but if you already deal with irritable bowel syndrome or chronic bloating, seltzer can make those symptoms more noticeable.
The relationship between carbonated water and acid reflux is less clear-cut than many people assume. Carbonated beverages are thought to relax the muscular valve between your esophagus and stomach, potentially allowing acid to creep upward. However, research from Baylor College of Medicine notes that carbonated beverages have not been consistently shown to cause or worsen reflux symptoms in clinical studies, and there’s no direct evidence that they promote the condition. If you notice seltzer triggers heartburn for you personally, that’s worth paying attention to, but it’s not a universal effect.
It Might Make You Hungrier
One small but interesting finding: carbonation itself may influence appetite. A study covered by UCLA Health found that rats drinking plain or artificially sweetened carbonated water gained more weight over a year than those drinking flat water. The mechanism appeared to be ghrelin, a hormone that signals hunger. When researchers tested 20 men rotating through four different beverages, those who drank carbonated water (sweetened or not) had triple the blood levels of ghrelin compared to those who drank still water or degassed sparkling water. The researchers concluded that carbon dioxide itself drove the increase in ghrelin production.
This is a single study with a small human sample, so it’s far from settled science. But if you’re trying to manage your weight and find yourself snacking more on days you drink a lot of seltzer, this could be part of the explanation.
It Doesn’t Weaken Your Bones
The idea that carbonated water leaches calcium from your bones has circulated for decades, and it’s not supported by evidence. A study published in the American Journal of Public Health examined bone mineral density in older women and found no association between carbonated beverage intake and bone loss after adjusting for factors like age, calcium intake, exercise, and hormone use. The confusion likely stems from research on cola specifically, where phosphoric acid (an ingredient in cola, not in seltzer) may play a role. Plain seltzer contains no phosphoric acid.
It Hydrates You Just Fine
Research shows sparkling and still water hydrate the body equally, with no significant difference in fluid retention or urine output. If seltzer helps you drink more water throughout the day because you enjoy the fizz, that’s a net positive for your health.
Not All Fizzy Water Is the Same
Seltzer, club soda, and tonic water often get lumped together, but their contents differ significantly. Plain seltzer is just water plus carbon dioxide, with no added minerals, zero sugar, and zero sodium. Club soda contains added minerals like potassium sulfate, sodium chloride, and sodium bicarbonate, contributing about 3% of your daily sodium value per 12-ounce serving. This is negligible for most people but can add up if you’re on a strict low-sodium diet and drinking several cans a day.
Tonic water is the outlier. A 12-ounce serving contains 32 grams of sugar, roughly the same as a can of soda. It also contains quinine, a compound originally used to treat malaria. If you’ve been drinking tonic water thinking it’s equivalent to seltzer, that’s a swap worth making.
The Bottom Line on Plain Seltzer
For most people, plain seltzer is a perfectly healthy choice. The potential downsides are modest: slight enamel erosion if you sip it constantly, possible bloating if your gut is sensitive, and a preliminary signal that carbonation could increase appetite hormones. Flavored varieties with citric acid carry more dental risk than plain. If you enjoy seltzer, drinking it with meals, choosing plain over citrus-flavored when possible, and not replacing all your tap water with it addresses virtually every concern in the research.