For years, diet soda has been positioned as the sensible alternative for people trying to cut back on sugar. A new study involving more than 103,000 participants suggests that framing may need to be reconsidered, particularly when it comes to liver health.
The research found that both sugar-sweetened and low or non-sugar-sweetened beverages were associated with a meaningfully higher risk of developing metabolic dysfunction-associated steatotic liver disease, a condition in which fat accumulates in the liver without alcohol as a cause. The condition can progress to more serious liver damage and is also linked to elevated cardiovascular risk.
What the study found
Participants who consumed more than 330 grams of either beverage type daily, roughly one standard can, were found to carry a significantly elevated risk of developing the liver condition compared to those who drank less. Sugar-sweetened beverages were associated with a 50% greater risk. Low or non-sugar-sweetened beverages showed an even higher association at 60%.
Diet drinks were also linked to a higher risk of liver-related mortality, a finding that researchers described as particularly notable given the widespread assumption that artificially sweetened beverages are a neutral or beneficial swap.
The study drew on data from the UK Biobank, following participants over a median period of more than ten years. During that time, 949 participants developed the liver condition and 103 died from liver-related causes. Liver fat content was assessed using MRI data, and participants reported their own beverage consumption throughout the study period.
The water finding
One of the more actionable findings from the research involves what happens when either type of soda is replaced with water. Substituting 330 grams of sugar-sweetened beverages with water was associated with a 14.7% reduction in liver disease risk. A similar substitution away from diet drinks showed comparable benefit.
Switching between the two types of sodas, however, produced no protective effect. The data suggests the benefit comes specifically from replacing either type with water, not from choosing one soda over the other.
What experts say
A graduate student involved in the study noted that low or non-sugar-sweetened beverages, widely perceived as the healthier option, still carry measurable risks to liver health. That assessment challenges a belief that has shaped consumer behavior and marketing for decades.
A registered dietitian nutritionist consulted in reporting on the findings advised prioritizing water or carbonated water over diet sodas, noting that zero-calorie labeling does not guarantee a product is without health consequences. Artificial ingredients in many diet beverages may carry their own effects that are not yet fully understood.
Limitations worth noting
The study has not yet been published in a peer-reviewed journal, and its findings should be treated as preliminary. Self-reported beverage intake introduces the possibility of inaccuracy.
Researchers have called for follow-up studies involving more diverse populations and longer tracking periods, as well as work to identify the biological pathways through which artificially sweetened beverages may affect liver function.
The full picture is still developing. What the current data makes clear is that zero calories soda does not mean zero consequences, and water remains the option with the most consistent evidence behind it.
