Carbonated Water vs. Flat Water: Types, Similarities and Differences

Drinking enough water is important for your overall health. It helps you stay hydrated and energized, and it supports your body as it carries out all of its essential processes.

But when you're tallying your fluid intake for the day, you may wonder: Does seltzer water "count" as water? And what are the differences between carbonated waters and regular, flat water?

In short: Both carbonated and flat water are great ways to stay hydrated, and both have health benefits, although there are some potential side effects of carbonated water to keep in mind.

To that end, before we dive into all the similarities and differences between flat and carbonated water, let's first talk about one important health issue many people ‌think‌ is connected to carbonated water: kidney stones.

There's no known link between carbonated water and kidney stones. In fact, there's no evidence at all that carbonated water causes kidney stones or that any variation — think: seltzer water, sparkling water, club soda — leads to poor kidney health.

On the contrary, one of the benefits of carbonated water is that it can help you stay properly hydrated, which can flush toxins out of your kidneys and help prevent kidney stones and related issues like bladder and kidney infections, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

Kidney stones are hard deposits made from minerals and salts — such as calcium, struvite, uric acid and cystine — that can form inside your kidneys, per the Mayo Clinic.

Symptoms of kidney stones include severe pain in the back and sides, pain while urinating and urine that's red, brown, pink, cloudy or foul-smelling, per the National Kidney Foundation. You can pass kidney stones through urination or have larger stones treated with sound waves to break them into smaller pieces.

Because high levels of sodium and/or calcium in your diet can sometimes lead to kidney stones, per the NIDDK, some people think club soda (a type of carbonated water) can cause these stones to develop.

The USDA estimates that a 12 fluid-ounce can or bottle of club soda contains almost 75 milligrams of sodium, as well as 17 milligrams of calcium.

To put that into perspective: Adults should aim for no more than 2,300 milligrams of sodium per day, according to the Dietary Guidelines for Americans. And they should get somewhere between 1,000 and 1,200 milligrams of calcium, per the National Institutes of Health.

Club soda is only a concern, then, if you are drinking it excessively and eating other foods high in sodium or foods high in calcium that could contribute to kidney stone development.

Ultimately, carbonated water can help you stay hydrated, which is important for overall kidney health, and it's a better choice than beverages like soda, which contain added sugar and calories.

No matter if you choose carbonated or flat water for hydration, both can have a positive effect on your health, including your kidney health.

Each type of carbonated water is a little different, though, so it may be helpful to know about each type. Refer to the table below:

Does sparkling water count as water? Yes, and whatever you reach for (carbonated or flat), there are some helpful similarities to know:

Both carbonated water and flat water are much better nutritional choices than sugary sodas. Most types of carbonated water and flat water are zero calories and contain zero grams of sugar.

But when you drink soda, you are getting extra calories and sugar, and drinking it is linked to chronic health problems like type 2 diabetes and heart disease, per Harvard Health Publishing.

(Keep in mind, however, that some brands of carbonated water have flavored versions that may be higher in calories.)

Dehydration is when you lose more fluid than you take in, per the Mayo Clinic. If your body doesn't have enough water to carry out its normal functions and the fluid lost isn't replaced, you will get dehydrated.

So, does carbonated water dehydrate you? No — drinking water, whether it's flat or carbonated, can help you stay hydrated and reverse dehydration. And, both can flush out bacteria in the bladder, stabilize heartbeat, regulate body temperature, maintain electrolyte balance and carry nutrients and oxygen to the cells of the body.

Bottled water brands like Dasani don't dehydrate you, either, so they're good options, too.

Is sparkling water good for weight loss? It can be, as can flat water.

When you are properly hydrated, you are less likely to overeat and may feel fuller faster. Hydration may also help stimulate fat breakdown (a process called lipolysis), per an August 2019 review in ‌Nutrients‌.

Drinking water can also ramp up your metabolism, through a process called thermogenesis, or heat production. When you drink chilled water, your body expends energy to warm itself up, per Johns Hopkins University. When the body's temperature is lowered, you expend more energy to warm it up.

What's more: Drinking carbonated or flat water instead of sugary beverages like soda can help you take in fewer calories, which can help when you're trying to lose weight.

However, drinking water can only do so much — if you don't make other lifestyle changes, such as getting regular exercise and eating a balanced diet, you're unlikely to see any significant weight loss.

While carbonated water is slightly more acidic than flat water, both options are significantly less acidic than soda, juices and other beverages.

You might have heard that carbonated water depletes calcium from the bones and damages teeth due to its acidity, but these are myths. Unflavored sparkling water has the same effect on your teeth as plain water, according to the American Dental Association (ADA).

Be aware, though, that citrus-flavored carbonated water and any carbonated water with added sugar can hurt your teeth and lead to cavities, per the ADA.

Depending on the brand, some bottled flat water can come from the same underground sources (such as springs) that sparkling water does.

This means both flat and carbonated water may contain small amounts of minerals such as calcium, magnesium, potassium, iron, chromium, selenium and other nutrients, according to a December 2016 mini-review in ‌Clinical Cases in Mineral and Bone Metabolism.‌

Carbonated water vs. flat water: Even though both are H2O, there are some slight differences between the two to know. They include:

The table above mentions that many types of carbonated water will have a slightly bitter taste due to the presence of carbon dioxide gas. And club soda will have a slightly salty taste due to its sodium bicarbonate content.

Turns out, the bubbles from sparkling water can make you feel full.

In a clinical trial, healthy young adults who drank carbonated water reported greater satiety than those who drank regular water or no water at all, per a February 2012 study in the ‌Journal of Nutritional Science and Vitaminology‌. Keep in mind, though, that this study is old and small; more research is needed to confirm the appetite-suppressing effects of carbonated water.

The gas in carbonated water may cause you to feel slightly bloated and gassy, per the Cleveland Clinic. Even a cup or two can make you feel that uncomfortable bloat.

This is a case where flat water can come in handy. It can hydrate you without causing excessive bloat, and may even help minimize bloating you feel at night or first thing in the morning.

If you do want to drink carbonated water for an upset stomach (sometimes fizzy drinks like ginger ale can help), reach for mineral water that contains chloride, magnesium, sulfate and other trace elements that promote digestive health, per the ‌Clinical Cases in Mineral and Bone Metabolism‌ review.

You can also keep the amount of carbonated water you consume each day in check, opting for flat water whenever you can.

If you have acid reflux, drinking a fizzy beverage like carbonated water could trigger symptoms like heartburn, per UChicagoMedicine.

You can alleviate this by drinking carbonated water in moderation, or sticking to flat water whenever possible. You can also try other natural remedies for heartburn.

If you opt for flat water, especially from the tap, it's likely going to have levels of fluoride in it. Fluoride is added to community water supply to reduce tooth decay and promote good oral health, per the Centers for Disease Control and Prevention (CDC).

While there are plenty of modern-day, healthy sources of fluoride (through toothpaste, mouthwash and taking trips to the dentist), drinking water that contains fluoride could also help protect your teeth.

Carbonated water, on the other hand, is not likely to have enough fluoride in it to have a positive effect on oral health, unless you make your own carbonated water with a SodaStream ($159.95 on Amazon) and tap water.

Drinking flat water from the tap (with a reusable water bottle) is a great way to stay hydrated while keeping your carbon footprint in check. Bottled water, on the other hand — which is how most of us access carbonated water — uses 11 to 20 times more energy than tap water, according to the Massachusetts Water Resources Authority.

What's more, bottled water contributes more waste: There are more than 2 million tons of plastic water bottles in U.S. landfills, and just one plastic bottle takes more than 1,000 years to break down, according to The Water Project. (And yes, it's a bad idea to reuse a plastic water bottle.)

Flat water typically comes from municipal sources. Then, impurities like dirt and debris are removed through processes like distillation, reverse osmosis, ozonation and other methods, per the U.S. Environmental Protection Agency (EPA).

But sparkling water does not go through a distillation process. Impurities are removed through other methods, and the step of infusing carbon dioxide gas is added (if it doesn't come from a naturally sparkling source).

Carbonated water and flat water are very similar as far as health benefits go. They are both hydrating, may aid in weight-loss efforts, are less acidic than some other beverages and can contain some essential minerals.

They are often processed differently, though, and carbonated water may trigger bloating and heartburn for some people.

Additionally, both carbonated and flat water are beneficial for kidney health and can help prevent kidney stones by keeping you hydrated, flushing out toxins and waste and preventing kidney infections.