Mountain Dew Zero won’t poison you with a single can, but drinking it regularly exposes you to a cocktail of artificial sweeteners, acids, preservatives, and caffeine whose long-term effects are still being untangled by researchers. The drink swaps sugar for a blend of aspartame, acesulfame potassium, and sucralose, which eliminates calories but introduces its own set of concerns across metabolic, cardiovascular, dental, and kidney health. None of these risks are dramatic enough to land you in the emergency room, yet the accumulating evidence suggests that treating zero-calorie soda as harmless water with flavor is a mistake.
What You’re Actually Drinking
Mountain Dew Zero Sugar contains no calories and no sugar. Its sweetness comes from three artificial sweeteners working together: aspartame, acesulfame potassium (ace-K), and sucralose. It also contains about 68 milligrams of caffeine per 12-ounce can, citric acid for tartness, sodium benzoate as a preservative, and Yellow 5 (tartrazine) for its signature neon color. Each of these ingredients has been studied independently, and the picture that emerges is more complicated than “it’s fine because there’s no sugar.”
Sweeteners and Your Blood Sugar
One of the core selling points of zero-sugar soda is that it shouldn’t spike your blood sugar. That part holds up fairly well in the short term. A study that tested Diet Mountain Dew specifically found that drinking it did not alter blood glucose levels compared to plain seltzer water. However, the same study found that Diet Mountain Dew nudged up levels of GLP-1, a gut hormone involved in insulin signaling, and that insulin concentrations were slightly higher after all non-nutritive sweetener conditions, even without any change in blood sugar.1PubMed Central. Hormonal responses to non-nutritive sweeteners in water and diet soda In practical terms, the drink doesn’t dump glucose into your bloodstream the way regular Mountain Dew does. But it does appear to trigger some of the hormonal machinery associated with sugar metabolism, and what that means over years of daily consumption is genuinely unclear.
Does It Help or Hurt Weight Loss?
This is where the evidence gets messy, because the answer depends on what you’re replacing and how your behavior changes afterward. A randomized trial that swapped people’s caloric beverages for diet drinks or water found that both substitutions led to roughly the same weight loss over six months, around two to two and a half percent of body weight. People assigned to diet beverages were actually twice as likely to hit the five-percent weight loss mark compared to a control group that just received general advice.2The American Journal of Clinical Nutrition. Replacing caloric beverages with water or diet beverages for weight loss in adults: main results of the Choose Healthy Options Consciously Everyday (CHOICE) randomized clinical trial An older controlled study similarly found that drinking aspartame-sweetened soda for three weeks reduced calorie intake and body weight compared to drinking soda sweetened with high-fructose corn syrup.3The American Journal of Clinical Nutrition. Effect of drinking soda sweetened with aspartame or high-fructose corn syrup on food intake and body weight
The complication comes from a large national survey finding that overweight and obese adults who drank diet beverages ate more solid food than those who drank regular soda, enough to partially offset the calorie savings. Obese diet-soda drinkers consumed roughly 194 extra calories per day from food compared to obese people drinking sugary soda.4PubMed Central. Diet-Beverage Consumption and Caloric Intake Among US Adults, Overall and by Body Weight That’s an observational finding, so it can’t tell you whether diet soda caused the extra eating or whether people who eat more simply gravitate toward diet drinks as a compensatory habit. Still, the pattern is consistent enough to be worth knowing about. If you switch to Mountain Dew Zero and unconsciously give yourself permission to eat larger meals, the calorie math may not work out the way you expect.
Gut Microbiome Effects
Some of the most provocative research on artificial sweeteners in recent years involves the gut microbiome. A widely cited 2014 study in mice found that consuming common non-nutritive sweeteners, including saccharin, altered the composition and function of intestinal bacteria in ways that drove glucose intolerance. The researchers showed this was genuinely a microbiome effect by transplanting gut bacteria from sweetener-fed mice into germ-free mice and seeing the metabolic problems transfer along with them. A small follow-up in healthy humans showed a similar pattern of disrupted blood sugar control after short-term saccharin use.5Nature. Artificial sweeteners induce glucose intolerance by altering the gut microbiota
That study made headlines, but the broader picture in humans is less alarming. A 2023 review of the evidence found that while some human trials did observe changes in gut bacteria from sweetener consumption, many well-designed randomized controlled trials found no significant effects on microbiome composition. The inconsistency likely comes from differences in the sweeteners tested, baseline diets, and the sheer variability of people’s existing gut bacteria.6PubMed Central. Effect of Non-Nutritive Sweeteners on the Gut Microbiota Mountain Dew Zero’s triple-sweetener blend hasn’t been tested as a combination in microbiome studies, so you’re extrapolating from research on individual sweeteners. The honest summary: the gut-health concern is plausible but far from settled.
Heart Health Signals
Cardiovascular risk is where the epidemiological data gets uncomfortable. A large French cohort study found that people who consumed above-average amounts of artificial sweeteners had a modestly higher risk of cardiovascular disease overall. The association was stronger for cerebrovascular events like stroke, where the risk was about 18 percent higher among higher consumers. Aspartame was specifically linked to elevated stroke risk, while acesulfame potassium and sucralose were each associated with higher coronary heart disease risk.7PubMed. Artificial sweeteners and risk of cardiovascular diseases: results from the prospective NutriNet-Santé cohort Mountain Dew Zero contains all three of those sweeteners.
A separate analysis using UK Biobank data confirmed a similar direction, finding that each additional teaspoon of artificial sweetener was associated with a small but statistically significant bump in overall cardiovascular disease risk and a somewhat larger increase in peripheral arterial disease risk.8PubMed Central. Artificial sweeteners and risk of incident cardiovascular disease and mortality: evidence from UK Biobank Both of these are observational studies, which means they can identify correlations but can’t prove that the sweeteners directly caused the heart problems. It’s possible that people who drink more diet soda already have other risk factors that explain the association. But the consistency of the signal across different populations and sweetener types is enough that researchers are paying attention.
A related but distinct finding involves erythritol, a sugar alcohol used in some zero-calorie products, though not in Mountain Dew Zero. Research found erythritol was associated with roughly double the risk of major cardiac events in people already at cardiovascular risk, and that it enhanced blood clotting at levels reached after normal consumption.9Nature Medicine. The artificial sweetener erythritol and cardiovascular event risk This is worth mentioning because it illustrates that different sweeteners carry different risks, and the heart-related concerns aren’t just about one bad actor.
Your Teeth Still Take a Hit
Ditching sugar removes one major threat to your teeth, but Mountain Dew Zero’s acidity is still a problem. The drink contains citric acid, which gives it that sharp citrus bite. Lab studies show that citric acid causes significantly more enamel erosion than phosphoric acid (the main acid in colas) across the same pH range.10Journal of Oral Rehabilitation. The effect of pH on the erosion of dentine and enamel by dietary acids in vitro The sugar in regular soda feeds bacteria that produce even more acid on top of the drink’s inherent acidity, creating a double threat.11PubMed Central. Dental erosion and severe tooth decay related to soft drinks: a case report and literature review Mountain Dew Zero eliminates that bacterial acid production, so it’s genuinely better for your teeth than the sugared version. But sipping any highly acidic drink throughout the day still softens enamel over time. Drinking it with meals rather than between them, and rinsing with water afterward, limits the damage.
Kidney Function Over the Long Haul
Two studies in this space paint a concerning picture for heavy diet soda drinkers. A study following participants over 23 years found that people who drank more than seven glasses of diet soda per week had roughly 83 percent higher odds of developing end-stage kidney disease compared to those who drank less than one glass per week, with a clear dose-response trend.12PubMed Central. Diet Soda Consumption and Risk of Incident End Stage Renal Disease A study focused on women found that consuming two or more servings of artificially sweetened soda per day was associated with roughly double the odds of significant kidney function decline.13PubMed Central. Associations of sugar and artificially sweetened soda with albuminuria and kidney function decline in women
Again, these are observational findings. People who already have metabolic risk factors or early kidney trouble might be more likely to switch to diet soda, which muddies the cause-and-effect picture. But the consistency of the dose-response relationship across studies suggests something real is going on. If you’re drinking several cans a day, the kidney data is one of the stronger reasons to cut back.
The Aspartame and Cancer Question
In 2023, the International Agency for Research on Cancer (IARC) classified aspartame as “possibly carcinogenic to humans,” which generated a wave of alarming headlines. But context matters. That same year, the Joint Expert Committee on Food Additives (JECFA) reaffirmed aspartame’s safety, concluding that the epidemiological evidence for a cancer link was “not convincing” and that bias, confounding, and reverse causality couldn’t be ruled out in the studies that did show associations. IARC itself acknowledged that chance, bias, or confounding could explain the positive findings it reviewed, particularly in three studies on liver cancer it considered higher quality.14PubMed Central. Perspectives on recent reviews of aspartame cancer epidemiology
A more recent integrative analysis using data mining and network modeling suggested that artificial sweeteners could increase risk for several cancer types, including kidney and breast cancer, through multiple biological pathways.15PubMed Central. An integrative analysis reveals cancer risk associated with artificial sweeteners That kind of computational work generates hypotheses rather than confirming them, and it hasn’t been validated in large-scale human trials. The honest state of the science is that aspartame at typical consumption levels probably doesn’t meaningfully raise your cancer risk, but the evidence isn’t clean enough for anyone to say that with full confidence. JECFA’s existing acceptable daily intake for aspartame, which translates to roughly 12 to 15 cans of diet soda per day for an average adult, remains unchanged.
Pregnancy Deserves Extra Caution
Pregnant women face a different risk calculus. A large Danish cohort study of nearly 60,000 pregnant women found that those who drank four or more servings per day of artificially sweetened carbonated soft drinks had about 78 percent higher odds of preterm delivery compared to women who consumed none.16The American Journal of Clinical Nutrition. Intake of artificially sweetened soft drinks and risk of preterm delivery: a prospective cohort study in 59,334 Danish pregnant women Animal research has also shown that maternal consumption of non-nutritive sweeteners can alter sweet taste preference in offspring and lead to metabolic issues later in life, including higher body mass and disrupted gut bacteria.17American Journal of Obstetrics and Gynecology. Consumption of non-nutritive sweeteners during pregnancy
A case-control study also found that daily early-life exposure to diet soda and aspartame was associated with roughly triple the odds of autism in males, though the sample sizes were small and the confidence intervals wide.18PubMed Central. Daily Early-Life Exposures to Diet Soda and Aspartame Are Associated with Autism in Males: A Case-Control Study None of this research is definitive, and most obstetric guidelines still consider moderate artificial sweetener use acceptable during pregnancy. But the precautionary signal is strong enough that limiting intake during pregnancy makes sense, especially since the benefit is just flavor.
Caffeine, Dependence, and Your Brain
At about 68 milligrams per 12-ounce can, Mountain Dew Zero carries more caffeine than most colas but less than a standard cup of coffee. One can won’t cause problems for most adults, but if you’re drinking two or three cans daily, you’re in the range where dependence becomes likely. Caffeine meets all the clinical criteria for an addictive substance, including tolerance, withdrawal, and dependence. Chronic overconsumption can produce a constellation of symptoms including irritability, tremors, heart palpitations, and digestive issues.19The Journal for Nurse Practitioners. Caffeine Intoxication and Addiction
A small study also found that caffeinated artificially sweetened soft drinks reduced blood flow velocity in major brain arteries compared to plain water, and that the artificially sweetened version showed slightly more pronounced effects on cerebrovascular reactivity than the sugar-sweetened version.20Frontiers in Human Neuroscience. Cerebral vascular function following the acute consumption of caffeinated artificially- and sugar sweetened soft drinks in healthy adults This was a small, acute study, and the clinical significance of temporary reductions in cerebral blood flow in healthy people is uncertain. But it hints at vascular effects that go beyond what caffeine alone would explain.
How Zero-Sugar Soda Tricks Your Reward System
One of the more interesting lines of research involves what artificial sweeteners do to your brain’s reward circuitry. When you eat real sugar, the sweetness on your tongue and the calories hitting your gut send aligned signals: the reward was real, reinforcing the behavior. Non-nutritive sweeteners deliver the sweetness signal without the caloric payoff. Over time, this mismatch appears to weaken the brain’s reward prediction system, altering dopamine signaling and affecting neuropeptides like orexin and oxytocin that help regulate appetite and motivation.21PubMed Central. Disrupting the Gut-Brain Axis: How Artificial Sweeteners Rewire Microbiota and Reward Pathways
The practical worry is that this disconnect could drive cravings for sweet or calorie-dense foods through other channels, which may help explain the observational finding about diet soda drinkers eating more solid food discussed earlier. Your brain expected calories and didn’t get them, so it goes looking for them elsewhere. This research is still in its early stages, and not every person experiences the same reward-pathway shifts. But it reframes diet soda as something other than a simple zero-consequence swap: you’re introducing a novel sensory-metabolic experience that your brain was not designed for.
Sodium Benzoate and Yellow 5
Beyond the sweeteners, Mountain Dew Zero contains sodium benzoate as a preservative and tartrazine (Yellow 5) as a colorant. Sodium benzoate is approved at the levels found in soft drinks, but research has flagged concerns at broader exposure levels, including oxidative stress, hormonal disruption, and mutagenic effects in lab settings.22PubMed Central. Sodium Benzoate-Harmfulness and Potential Use in Therapies for Disorders Related to the Nervous System: A Review When sodium benzoate combines with ascorbic acid (vitamin C), it can form benzene, a known carcinogen, though the levels found in beverages are typically very low. The growing use of sodium benzoate across processed foods means your total daily exposure may be higher than any single product suggests.23Results in Chemistry. A critical review on sodium benzoate from health effects to analytical methods
Tartrazine has been studied mostly for toxicological effects at various doses. A review of the literature found evidence of toxic effects in animal models at doses at or even below the acceptable daily intake, including developmental abnormalities in zebrafish embryos.24Revista Brasileira de Ciências Ambientais. Toxicological and ecotoxicological aspects of tartrazine yellow food dye: a literature review Translating fish embryo studies to human health is a stretch, but the Yellow 5 concern has also fueled broader debates about synthetic food dyes and behavioral effects in children. If you’re drinking Mountain Dew Zero primarily for the caffeine kick, it’s worth noting that you’re also getting dye and preservative exposures you wouldn’t get from coffee or tea.
Bone Health and Soft Drink Consumption
A common concern with soda consumption, diet or otherwise, involves bone density. A seven-year follow-up study found a strong dose-response relationship between soft drink consumption and fracture risk: daily consumers had nearly five times the adjusted fracture hazard compared to nonconsumers.25PubMed Central. High Consumption of Soft Drinks Is Associated with an Increased Risk of Fracture: A 7-Year Follow-Up Study However, that study grouped all soft drinks together and didn’t isolate diet varieties. A study focused specifically on soda and osteoporosis in postmenopausal women found no significant association between soda consumption and osteoporosis risk after adjusting for other factors.26PubMed Central. Soda intake and osteoporosis risk in postmenopausal American-Indian women
The mechanism people often point to is phosphoric acid leaching calcium from bones, but Mountain Dew Zero uses citric acid rather than phosphoric acid. The more likely pathway, if there is one, is displacement: people who drink a lot of soda tend to drink less milk and consume less calcium overall. That’s a dietary pattern problem rather than a direct chemical effect, and it applies to any beverage that displaces nutrient-rich alternatives.
Packaging and Chemical Migration
One risk that rarely makes it into the diet soda conversation has nothing to do with the recipe itself. Bisphenols, used in the production of certain plastic materials and can linings, can migrate into beverages over time. A review of the research noted that this migration from food-contact materials changes the properties of the products and can cause harmful effects on health, particularly when exposure exceeds regulatory thresholds.27Journal of Separation Science. Bisphenol A and its analogs migrated from contact materials into food and beverages: An updated review in sample preparation approaches This isn’t unique to Mountain Dew Zero and applies to essentially anything sold in plastic bottles or lined cans. But it adds one more low-level chemical exposure to the pile, particularly if you store cans in warm environments where migration accelerates. Choosing the fountain version or glass bottles, when available, sidesteps this concern entirely.