Fizzy Drinks Linked to Bloating, Heart Disease, and Liver Cancer – Here’s the Science

A can of cola or a diet soda might seem harmless, but emerging evidence suggests that habitual fizzy drink consumption is tied to a surprisingly broad range of health risks, including bloating, cardiovascular disease, and liver cancer. The research is not yet definitive, but the pattern across dozens of studies is consistent enough that dietitians and public health bodies are paying close attention. Understanding what these drinks actually do inside the body, and what the evidence does and does not prove, matters for anyone who reaches for a fizzy drink most days.

What Regular Fizzy Drink Consumption Is Associated With

The headline findings are striking. An umbrella review of 47 meta-analyses of observational studies found that 79% of those analyses showed direct associations between greater sugar-sweetened beverage consumption and worse health outcomes. The conditions with the strongest evidence included depression, cardiovascular disease, type 2 diabetes, and nonalcoholic fatty liver disease. A separate umbrella review linking sweetened beverages to cardiovascular mortality found that sugar-sweetened drinks were associated with a 9% higher overall mortality risk, while artificially sweetened beverages were tied to a 10% increase. These are associations from observational data, not proof of direct causation, but the signal is consistent enough to take seriously.

Liver disease is an area where the data is particularly pointed. A large prospective cohort study following postmenopausal women for more than 20 years found that consuming one or more sugar-sweetened beverages per day was linked to significantly higher liver cancer incidence and death from chronic liver diseases. Liver cancer is often diagnosed late and carries a poor prognosis, which makes any modifiable dietary risk factor worth scrutinizing.

Why the Gut Feels It First

For most people, the most immediate effect of a fizzy drink is digestive. The carbonation in these drinks introduces carbon dioxide into the gastrointestinal tract, contributing to bloating, belching, and abdominal discomfort, particularly in people who already have a sensitive gut. For the roughly 10 to 20% of adults who live with irritable bowel syndrome (IBS), a chronic functional gastrointestinal disorder that causes significant daily disruption, fizzy drinks sit on the list of first-line things to limit.

The British Dietetic Association's updated dietary guidelines for IBS management, which reviewed 86 studies and produced 46 evidence statements and 15 clinical recommendations, explicitly list limiting fizzy drinks alongside limiting alcohol and caffeine as foundational advice. The BDA's simplified dietary algorithm starts with healthy eating adjustments, including cutting back on carbonated beverages, before moving on to more advanced interventions like the low FODMAP diet, which targets fermentable carbohydrates and is designed to be implemented under the supervision of a dietitian. Fizzy drinks, especially those containing fermentable sugars or sugar alcohols, can aggravate the very symptoms IBS patients are trying to manage.

Children and Adolescents Face Compounded Risks

The risks are not confined to adults. A USDA systematic review on sugary drinks and childhood obesity concluded, based on moderate evidence, that sugar-sweetened beverage consumption by infants, children, and adolescents is associated with unfavorable body composition and a higher risk of obesity. Excess weight gained in childhood and adolescence is not easily shed and is associated with elevated risks of type 2 diabetes, cardiovascular disease, and metabolic dysfunction later in life. Fizzy drinks are among the easiest high-calorie, low-nutrient items to remove from a young person's diet, making them a frequent early target in pediatric dietary counseling.

Are Diet Drinks a Safe Alternative?

Switching from sugar-sweetened to artificially sweetened beverages sounds logical, but the evidence on diet drinks is more complicated than the marketing suggests. Some research points to diet sodas carrying their own elevated risks: the cardiovascular umbrella review found a 10% higher mortality risk associated with artificially sweetened beverages, and a review examining artificial sweeteners and health risks noted that it remains unclear whether diet soft drinks should be recommended as a healthier alternative, given that some studies flag increased risks for certain conditions. Carbonation-related bloating applies equally to diet variants, and the palatability of very sweet drinks may reinforce a preference for sweetness that makes dietary change harder overall.

The BDA guidelines do not endorse diet fizzy drinks as a substitute; the recommendation is simply to reduce fizzy drink consumption across the board.

What Cutting Back Actually Looks Like

The practical picture from the BDA's 15 clinical recommendations is not about perfection. For most people, especially those managing IBS or a chronic condition, the initial advice is straightforward: limit alcohol, caffeine, and fizzy drinks; eat in a calm environment; and ensure adequate fluid intake from uncaffeinated sources. For constipation-predominant IBS specifically, the guidelines recommend gradually increasing fibre intake and considering linseed supplementation alongside these baseline changes.

None of this requires eliminating fizzy drinks from the universe. But the cumulative weight of the evidence suggests that daily or near-daily consumption, particularly of sugar-sweetened varieties, carries real associated risks across multiple organ systems. For anyone already managing a digestive condition, the gut-level discomfort alone is usually a sufficient motivator. For everyone else, the associations with cardiovascular disease and liver cancer in long-term studies make a strong case for treating fizzy drinks as an occasional item rather than a daily staple.

Evidence rating

EMERGING — 80/100

Caveats:

• These are guideline recommendations synthesized from 86 studies, not a single clinical trial — individual studies varied in design quality and population size.
• The evidence base was drawn from literature up to October 2015; more recent RCT data on low-FODMAP and probiotics may affect some recommendations.
• Funding source was not disclosed by the authors.
• The low-FODMAP diet component of these guidelines is explicitly intended to be supervised by a registered dietitian and should not be self-administered without professional guidance.
• The guideline notes that other conditions such as coeliac disease must be ruled out before dietary interventions for IBS are initiated.

Systematic review critically appraising 86 studies to generate 46 evidence statements and 15 clinical recommendations for IBS dietary management. The review synthesizes association and intervention data across multiple diet-related topics; it reflects the weight of available evidence rather than establishing new causal mechanisms. Literature search was conducted to October 2015, and some recommendations note the need for better-powered RCTs.

References

1. Y. A. McKenzie, R. K. Bowyer, H. Leach, et al. (2016). British Dietetic Association systematic review and evidence‐based practice guidelines for the dietary management of irritable bowel syndrome in adults (2016 update). Journal of Human Nutrition and Dietetics. https://doi.org/10.1111/jhn.12385
2. Melissa M. Lane, Nikolaj Travica, Elizabeth Gamage, et al. (2024). Sugar-Sweetened Beverages and Adverse Human Health Outcomes: An Umbrella Review of Meta-Analyses of Observational Studies. Annual Review of Nutrition. https://doi.org/10.1146/annurev-nutr-062322-020650
3. Mehrdad Jamali, Paniz Anvarifard, Banafshe Hosseini, et al. (2025). Sweetened beverages and cardiovascular outcomes: an umbrella review of mortality and health outcomes. Nutrition Journal. https://doi.org/10.1186/s12937-025-01242-1
4. Sugar-Sweetened and Artificially Sweetened Beverages and Risk of Liver Cancer and Chronic Liver Disease Mortality – PMC. NIH. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9684947/
5. What is the relationship between sugar-sweetened beverage consumption and growth, body composition, and risk of obesity? – USDA's Nutrition Evidence Systematic Review. nesr.usda.gov. https://nesr.usda.gov/2020-dgac-report/part-d/chapter-1/sugar-sweetened-beverage-conclusion-statement-1
6. Dagfinn Aune (2012). Soft drinks, aspartame, and the risk of cancer and cardiovascular disease. The American Journal of Clinical Nutrition. https://doi.org/10.3945/ajcn.112.051417