Water and Sparkling Water: What Is Actually Known

2026-10-09 · by StepForge

People like to speak confidently about water: "drink two liters a day," "soda leaches calcium." I decided to check what actually stands behind these phrases. Below is what I managed to find and, above all, how strong the evidence is. Caveats matter more than usual here: there are few good trials specifically on sparkling water, and a lot rests on small studies.

How Much Water a Person Needs

The main thing to understand: all the "norms" refer to total water intake, meaning water from drinks and from food. Food provides roughly a fifth.

Source	Women	Men	What is counted
EFSA (Europe)	2.0 L/day	2.5 L/day	all water, temperate climate and activity
NASEM (USA)	2.7 L/day	3.7 L/day	all water; about 2.2 and 3.0 L of it from drinks

This is an adequate intake, not a requirement and not a prescription. The figures are derived from how much healthy people actually drink. NASEM's values are calculated for healthy, sedentary adults in a temperate climate: heat and exertion increase water losses. It also states that the evidence for recommendations "for the prevention of chronic disease" is insufficient, and that the norm is meant to prevent dehydration.

So "drink 2-3 liters of water" doesn't work literally: those liters include tea, soup, and the moisture in food. A simpler practical guide is to drink when you're thirsty, and a bit more in the heat and during exertion.

Can You Drink Too Much

As far as I found, no tolerable upper intake level has been set for water, but an excess can dilute the sodium in the blood (hyponatremia). This most often happens to athletes on long distances, and it isn't only about volume: in some people, vasopressin secretion persists during exertion, and the kidneys excrete water less well. It is often stated that healthy kidneys excrete about 0.8-1 L per hour, but the sources differ in their estimates (roughly 0.5 to 1.5 L/h). For everyday life the takeaway is simple: don't pour liters of water into yourself within an hour "on schedule." More detail: an overview of hyponatremia in athletes.

When You Should Deliberately Drink More

The strongest argument for "drink more" concerns kidney stones. In a five-year randomized trial (199 people after a first calcium stone), the group that increased their drinking to a urine output of about 2 L a day had recurrences in 12% of cases versus 27% in the control group. The Cochrane review relies on this single trial and gives a risk ratio of about 0.45. The sample is small, and these were people after a first stone, so there is less data for severe cases, but the direction is clear. Sources: Cochrane, analysis of the Borghi trial.

What Sparkling Water Is

It's water with dissolved carbon dioxide. Some of the CO₂ reacts with the water to form weak carbonic acid: it gives the characteristic tang and slightly lowers the pH.

Does It Hydrate as Well

Judging by the available data, yes. In a well-known study on the "beverage hydration index" (Maughan et al.), people drank a liter of various beverages, after which the urine they produced was measured. Sparkling water gave the same result as plain water, while milk, orange juice, and oral rehydration solutions came out ahead: thanks to electrolytes and energy, not bubbles. I couldn't find the primary source in open access, so I'm citing a retelling. A caveat: the index is measured over several hours after a single liter; it is not long-term water balance.

What Sparkling Water May Be Good For

A Replacement for Sugary Drinks

This is the main practical advantage. Sugary drinks are linked to weight gain and type 2 diabetes in observational studies, but such links don't prove causation. There is also a caveat about water: a 2022 network meta-analysis (17 trials, people with excess weight) found no separate effect from replacing sugary drinks with water, but did find a small effect from replacing them with drinks containing sweeteners. This doesn't mean water is useless: more likely, there are few trials and the question is open. Source: JAMA Network Open, 2022.

Digestion: Weak Data

The only coherent randomized blinded trial (Cuomo, 2002): 21 patients with dyspepsia and constipation drank sparkling or tap water for about 15 days. On sparkling water, dyspepsia and constipation symptoms decreased; on tap water they did not. But the sample is tiny, it's hard to mask bubbles, and the sparkling water there contained more minerals than the tap water, so the bubbles may have had nothing to do with it. Source: PubMed.

Satiety, contrary to popular belief, was not confirmed by this same trial: after sparkling water, people ate more calories in the satiety test than before it. So "bubbles fill the stomach and keep you from getting hungry" remains merely a hypothesis.

Minerals

If the water is mineral water, it may provide calcium, magnesium, and other minerals. But the benefit is determined by the composition, not the bubbles, and it varies greatly between brands: read the label.

Possible Downsides

Bloating, Belching, Reflux

In sensitive people, gas can cause bloating and belching. With reflux the picture is mixed: the studies were mostly done on sweet colas and sodas, not plain water. They show that a carbonated drink can lower the pressure of the lower esophageal sphincter and make it relax more often, but I found no separate large studies on unsweetened sparkling water in people with GERD. Reactions differ from person to person, so the only thing that helps is self-observation: small volumes, unhurried sips. An overview of the topic: systematic review on the GI tract.

Tooth Enamel

Laboratory studies show that acidic drinks can dissolve enamel. A 2023 systematic review of carbonated soft drinks confirms that most of them have a pH below the critical level for enamel (review). But these were mostly sweet and acidic drinks; plain sparkling water was not singled out. The American Dental Association considers sparkling water generally safe for teeth based on the available data (ADA). The situation is noticeably worse with "flavored" varieties, especially with citric acid and sugar, and the frequency and duration of contact matter: don't stretch one glass over the whole day.

Bones: The "Calcium Leaching" Myth

The scare grew out of studies on cola. In the Framingham study, women who drank cola had lower bone density in the hip, while other carbonated drinks showed no such link (retelling). Phosphoric acid and the overall diet are suspected, but this is observational data: causation is not proven. I found no convincing data on harm to bones from plain sparkling water.

Bladder

Doctors often advise giving up carbonated drinks for an overactive bladder, but there are no trials proving this helps. I also found no cohort data showing that soda causes urinary incontinence, so it can't be claimed. If frequent urges bother you, you can test it on yourself: cut out the carbonation for a couple of weeks and compare.

Sodium and Blood Pressure

WHO sets no health-based limit for sodium in water: there is only a taste threshold of about 200 mg/L. Some countries advise people on salt restriction to drink water with much less (on the order of 20 mg/L). More detail: 2025 review, WHO fact sheet, Health Canada. In a small trial, sparkling mineral water with sodium in the form of bicarbonate did not raise blood pressure (PubMed), and a 2024 systematic review calls the question of whether people with hypertension should avoid sparkling water open (review). Takeaway: look at the label, not the bubbles.

Where Else CO₂ Is Used

Carbon dioxide is used not only in drinks: in modified-atmosphere packaging (it suppresses the growth of many microbes and extends the shelf life of meat, fish, and ready meals), for decaffeinating coffee with supercritical CO₂, and for cooling (dry ice). In medicine it is used to inflate the abdominal cavity in laparoscopy. Here I relied on common knowledge, without separate references.

Which Water to Carbonate at Home

This is more engineering than medicine: there are no direct studies, so what follows is my practical summary.

Base. Ordinary clean drinking water works well: neutral taste and predictable composition. If your tap water has chlorine, you can run it through a carbon filter.
Mineral water can also be carbonated, but with high mineralization the taste changes and more scale builds up on the equipment. If you're restricting salt, check the sodium.
Spring and well water is fine only if you know its quality (there are test results): "spring" on its own guarantees nothing.
Carbonate to a comfortable level and alternate with still water.

Summary

Sparkling water hydrates just as well as still water.
The main advantage: replacing sugary drinks. The rest (digestion, satiety) is weakly supported.
The main downsides are individual: bloating and heartburn in sensitive people, acidic and sweet "flavored" varieties for teeth, sodium in some mineral waters.
The "calcium leaching" myth is about colas, not water.
The "2-3 liters" norm is all water, including food and tea; drink to thirst.

Sources

Discussion

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