MiO and similar liquid water enhancers are acidic, typically registering a pH well below the threshold at which tooth enamel begins to dissolve. The primary culprit is citric acid, which serves as both a flavoring agent and a preservative in the concentrated drops. But acidity is only part of the picture. MiO also contains artificial sweeteners like sucralose and acesulfame potassium, along with preservatives such as potassium sorbate and sodium benzoate, each of which carries its own set of questions about what happens in your mouth and further down your digestive tract.
How Acidic MiO Actually Is
Tooth enamel starts to erode when the pH of a liquid drops below roughly 5.5, a threshold dental researchers refer to as the critical pH for enamel dissolution.1PubMed. Pathogenesis and modifying factors of dental erosion MiO’s concentrate, before you add it to water, is extremely acidic. The exact pH varies by flavor, but independent measurements of citric-acid-based water enhancers consistently place them in the range of about 2.5 to 3.5 in their undiluted form. Even after squeezing a serving into a full glass of water, the resulting drink lands somewhere around pH 3 to 4, depending on how generous you are with the squeeze. That is comfortably in erosive territory, roughly comparable to many sports drinks and fruit juices.
This matters because your enamel cannot regenerate. Once it wears away, it is gone. The initial acid contact etches the enamel surface, softening the outermost layer so that even normal mechanical forces like chewing or brushing can strip it further. Repeated exposure over weeks and months is where the real damage accumulates. A single glass is not going to ruin your teeth, but sipping MiO-flavored water throughout the day is a different story.
Why pH Is Not the Whole Story
Acidity is measured two ways, and both matter. The first is pH, which tells you how many free hydrogen ions are floating around in the liquid right now. The second is titratable acidity, which captures the total reservoir of acid that can be released over time, including acid that has not yet dissociated. Dental researchers have found that both properties contribute to how much enamel a drink actually removes, with pH being the stronger predictor during initial contact and titratable acidity becoming more important during prolonged exposure.2Journal of Dental Sciences. Association of dental enamel loss with the pH and titratable acidity of beverages Beverages with high titratable acidity slow down the rate at which your saliva can neutralize the acid in your mouth, extending the window during which enamel softening continues.3PubMed. Effect of pH and titratable acidity on enamel and dentine erosion
Citric acid, the main acid in MiO, has a particularly high titratable acidity relative to its pH. It acts as a buffer, resisting the efforts of your saliva to push the pH in your mouth back toward neutral. This is why citric-acid-based drinks can be more erosive than their pH number alone would suggest. A drink with hydrochloric acid at the same pH would be easier for saliva to neutralize, because hydrochloric acid lacks that buffering capacity. Citric acid hangs around.
Does Dilution Help?
You might assume that because MiO gets mixed into a large volume of water, the dilution should largely cancel out the acid threat. The reality is more nuanced. Research on concentrated drink products found that dilution reduces titratable acidity proportionally, so the total acid load does drop as you add more water. But the pH changes very little with dilution, because citric acid’s buffering behavior means it stubbornly resists shifting toward neutral even at extreme dilution ratios.4PubMed. The pH and titratable acidity of a range of diluting drinks and their potential effect on dental erosion So adding more water to your MiO does lower the overall acid content per sip, which helps, but the pH of the finished drink remains low enough to soften enamel on contact.
There is a practical lesson here. If you are going to use MiO, using less concentrate per glass genuinely reduces the erosive potential, even if it does not bring the pH above that 5.5 safe zone. Every bit of dilution trims the total acid your teeth have to deal with over the course of each sip. And drinking the whole glass in a short sitting, rather than nursing it over hours, limits how many separate acid attacks your enamel endures.
What About Flavored Sparkling Water?
People who worry about MiO sometimes switch to flavored sparkling water as a supposedly gentler alternative. The carbonation itself contributes a small amount of carbonic acid, and added flavorings often include citric or malic acid. Lab testing of several commercial flavored sparkling waters found that all of them had pH values below the critical threshold for enamel, and that enamel specimens lost measurable mass starting from the very first day of immersion, with the erosion accumulating over time.5Brazilian Dental Science. The long-term effect of sparkling flavored water on human tooth enamel determined by gravimetric analysis: a preliminary evaluation Plain sparkling water without added flavoring is less of a concern because its pH, while slightly below 7, generally hovers close enough to neutral that erosion risk is minimal. The flavoring is what pushes it into problematic territory.
Calcium-fortified formulations are an interesting exception. One study comparing different blackcurrant juice concentrates found that versions reformulated with added calcium produced enamel loss that was statistically indistinguishable from water, while a standard fruit concentrate caused significantly more erosion.6PubMed Central. Development and evaluation of a low erosive blackcurrant juice drink. 3. Final drink and concentrate, formulae comparisons in situ and overview of the concept. Calcium in the liquid essentially resaturates the enamel surface, counteracting the dissolving effect of the acid. MiO does not contain added calcium, so it does not benefit from this protective mechanism.
When to Brush After Drinking MiO
A common piece of dental advice says you should wait 30 to 60 minutes after consuming anything acidic before brushing your teeth, because brushing while enamel is acid-softened scrubs away more material. There is genuine evidence behind this idea. One study found that brushing immediately after exposure to an acidic soft drink caused the greatest irreversible loss of tooth structure, while waiting 60 or 120 minutes allowed the surface to reharden and reduced damage.7Journal of Microscopy. Potential effects of tooth‐brushing on human dentin wear following exposure to acidic soft drinks
That said, the picture is not perfectly clean. A systematic review looking specifically at enamel found that delaying brushing after an acid exposure did not consistently reduce erosive wear in human enamel samples, even though it helped in bovine enamel experiments.8PubMed. Does delayed toothbrushing after the consumption of erosive foodstuffs or beverages decrease erosive tooth wear? A systematic review and meta-analysis The discrepancy likely reflects differences in how human and bovine enamel respond to remineralization, and the practical takeaway is still reasonable: if you have just been sipping something acidic, rinsing your mouth with plain water right away is a safer first step than reaching for the toothbrush.
The Sweetener Side of Things
MiO’s sweetness comes from sucralose and acesulfame potassium, both non-nutritive sweeteners that contribute zero calories. From a tooth-decay standpoint, this is actually a point in MiO’s favor. Dental cavities are driven by mouth bacteria fermenting sugar and producing acid as a byproduct. Research on non-nutritive sweeteners has shown they suppress the growth and acid production of cavity-causing bacteria like Streptococcus mutans compared to sucrose, and they maintain a healthier balance of bacterial species in oral biofilms.9BioMed Research International. The Effects of Nonnutritive Sweeteners on the Cariogenic Potential of Oral Microbiome So while MiO’s acidity threatens enamel through direct chemical erosion, its sweeteners do not add the secondary threat of bacteria-driven decay the way sugar-sweetened drinks do.
The gut is a different conversation. Your saliva handles what happens in your mouth, but once sucralose reaches your intestines, it interacts with the trillions of bacteria living there. A study in healthy young adults found that ten weeks of sucralose consumption significantly reduced Lactobacillus acidophilus, a beneficial species, while increasing Blautia coccoides by three- to fourfold.10PubMed Central. Ten-Week Sucralose Consumption Induces Gut Dysbiosis and Altered Glucose and Insulin Levels in Healthy Young Adults A pair of randomized controlled trials in adults with type 2 diabetes found that replacing added sugars with sucralose reduced gut microbial diversity and depleted several types of beneficial Firmicutes bacteria, though adults who were overweight but not diabetic showed no significant changes.11PubMed Central. Effect of Replacing Added Sugars with Sucralose on Gut Microbiome Composition Among Asian Indian Adults in Two 12-week Randomized Controlled Trials The pattern that keeps emerging is that metabolic status seems to influence vulnerability: people whose blood sugar regulation is already compromised may be more susceptible to sucralose-driven shifts in gut bacteria.
Sweeteners and Blood Sugar
The most provocative finding in recent sweetener research links artificial sweeteners not just to microbial changes but to altered blood sugar control in some people. A 2022 randomized trial published in Cell tracked participants consuming saccharin, sucralose, stevia, or aspartame at doses within regulatory limits. Saccharin and sucralose significantly raised glycemic responses in “top responders.” When stool samples from those responders were transplanted into germ-free mice, the mice developed elevated blood sugar responses too, while transplants from non-responders and control subjects did not.12Cell. Personalized nutrition prediction of glycemic responses The implication is that sweetener-induced changes to gut bacteria can causally affect how well you regulate blood sugar, but the effect is highly individual. Some people’s microbiomes shift dramatically; others barely budge.
This is still a young area of research, and there is no clinical consensus that the doses in a few daily servings of MiO cause meaningful metabolic harm in most people. But if you use water enhancers as a constant companion throughout the day, the cumulative sweetener intake can climb. The U.S. acceptable daily intake for sucralose is 5 milligrams per kilogram of body weight, and a typical MiO serving contains a small fraction of that, but heavy users who squeeze liberally and drink multiple bottles a day can start approaching levels where these studies become more relevant.
The Preservatives in the Bottle
MiO’s ingredient list includes potassium sorbate and sodium benzoate, both common food preservatives that prevent microbial growth in the concentrated liquid. These are generally recognized as safe by regulatory agencies at approved levels, but recent research is raising questions about what they do to gut bacteria at typical dietary exposures.
A mouse study evaluating several antimicrobial food preservatives found that both sodium benzoate and potassium sorbate significantly altered gut microbiota composition, and that this effect was not limited to synthetic preservatives. Naturally derived antimicrobials like nisin and lysozyme shifted the gut community as well.13npj Science of Food. Systematic evaluation of antimicrobial food preservatives on glucose metabolism and gut microbiota in healthy mice A separate study in rats examined sodium benzoate, potassium sorbate, and citrate, both alone and in combination. All treatments significantly reduced Lactobacillus populations, and citrate combined with sodium benzoate produced the highest levels of Enterobacteriaceae, a bacterial family that includes several opportunistic pathogens.14Journal of the Science of Food and Agriculture. Beyond antimicrobial efficacy: Complex interactions of sodium benzoate, potassium sorbate, and citrate alter the rat gut microbiome That combination is worth noting because MiO contains all three ingredients: sodium benzoate, potassium sorbate, and citric acid.
Another mouse study on potassium sorbate found that continuous intake caused inflammatory cell infiltration in the liver and increased a marker of systemic inflammation, along with altered gut microbial abundances.15PubMed. Effects of potassium sorbate on systemic inflammation and gut microbiota in normal mice: A comparison of continuous intake and washout period These are animal studies with doses that may not translate directly to human consumption of a few squirts of MiO per day, but they suggest that the preservative component of water enhancers deserves attention alongside the sweeteners.
What Happens to the Gut Lining
Beyond shifting which bacteria thrive in your intestines, there is cell-level evidence that some artificial sweeteners may affect the intestinal barrier itself. A laboratory study using human intestinal epithelial cells found that sucralose and aspartame at low concentrations increased the permeability of the intestinal lining by disrupting tight junction proteins, specifically by causing a protein called claudin 3 to be pulled away from the cell surface. The effects were mediated through the sweet taste receptor T1R3, which exists not just on your tongue but also on cells lining your gut. Sucralose triggered this receptor to set off a chain of events that loosened the seal between intestinal cells.16PubMed Central. Artificial Sweeteners Disrupt Tight Junctions and Barrier Function in the Intestinal Epithelium through Activation of the Sweet Taste Receptor, T1R3
Increased intestinal permeability, sometimes informally called “leaky gut,” allows molecules to pass through the gut wall that would normally be kept out. Over time, this can contribute to low-grade inflammation. It is important to keep perspective here: this was a cell culture study, meaning researchers applied sweeteners directly to isolated cells in a dish, not inside a living human digestive system where dilution, mucus layers, and other protective mechanisms are at work. The findings are plausible and mechanistically interesting, but they have not yet been confirmed in well-controlled human studies at dietary-relevant doses.
Saliva Does a Lot of the Heavy Lifting
Your mouth has a built-in defense system against acid. Saliva steadily dilutes and washes away acidic residue, and its bicarbonate content actively buffers the pH back toward neutral.17PubMed Central. Saliva and dental erosion After a single acidic drink, saliva can restore mouth pH within about 20 to 30 minutes for most people. This is why the pattern of consumption matters more than the total volume. If you drink a glass of MiO-enhanced water in ten minutes, your saliva gets one acid challenge and one recovery period. If you sip it over three hours, your saliva never gets the chance to fully recover before the next sip resets the clock.
People with reduced saliva flow, whether from medications, medical conditions, or simply chronic dehydration, are at greater risk. Many common medications, including antihistamines, antidepressants, and blood pressure drugs, reduce salivary output as a side effect. If you are taking one of these and also sipping acidic water enhancers all day, the combination can accelerate enamel wear more than either factor alone.
Practical Ways to Reduce the Risks
None of this means you need to throw out your MiO bottle. The dose and the pattern make the poison. A few habits can substantially reduce both the dental and gut-related concerns:
- Use less concentrate: Every drop of MiO you skip lowers both the pH impact and the total acid, sweetener, and preservative load. If your drink still tastes good with a lighter squeeze, your teeth and gut benefit.
- Drink it in one sitting: Finish your flavored water within 20 to 30 minutes rather than sipping it across the morning. This limits the number of acid exposures your enamel endures and gives saliva time to do its job.
- Use a straw: Directing the liquid past your front teeth and toward the back of your mouth reduces contact between the acid and the enamel surfaces most visible when you smile.
- Rinse with plain water afterward: A quick swish of plain water helps clear residual acid from your mouth without the abrasion risk of brushing on softened enamel.
- Avoid using MiO as your only fluid: If water enhancers are the only way you stay hydrated, at least alternate with plain water. Making every sip acidic means your mouth is under constant assault.
For gut health, the calculus is harder because the research is still evolving and individual responses vary widely. People with existing metabolic conditions like type 2 diabetes may want to be more cautious about sustained high intake, given the emerging links between sucralose, gut microbial shifts, and glucose control. For healthy individuals, occasional or moderate use likely falls within what the body can handle without meaningful disruption, though the preservative findings are worth keeping an eye on as research matures.
What MiO Shares with Other Everyday Drinks
It helps to put MiO in context. Orange juice has a pH around 3.5 to 4.0 and high titratable acidity. Cola sits near pH 2.5. Black coffee is around 5.0. Apple juice is about 3.5. If you regularly drink any of these, your teeth are facing a similar acid challenge. The difference is behavioral: most people drink a glass of juice at breakfast and move on, while MiO’s design as a portable water enhancer encourages continuous sipping, which multiplies the exposure window. The product itself is not uniquely dangerous compared to other acidic drinks. The way people tend to use it is what elevates the risk.
Similarly, the sweetener and preservative concerns are not unique to MiO. Sucralose appears in thousands of food products, and potassium sorbate and sodium benzoate are nearly ubiquitous in processed foods and beverages. What makes water enhancers worth singling out is the perception of innocuousness. People think of MiO as “just flavored water” and may consume it more freely and more often than they would a can of soda, unaware that the acid load and additive exposure share much of the same chemistry.