Study links daily soda consumption to 60% increased fatty liver disease risk

A study presented at the United European Gastroenterology Week in Berlin has upended a common assumption about diet sodas: they may be worse for your liver than their sugary counterparts. Researchers tracking more than 124,000 people from the UK Biobank over a decade found that drinking just one can of diet soda daily raised the risk of nonalcoholic fatty liver disease by 60 percent, while regular sugary sodas increased it by 50 percent. None of the participants had liver disease when the study began. The findings challenge the widespread belief that diet beverages are a safer choice.

Nonalcoholic fatty liver disease, now formally called metabolic dysfunction-linked steatotic liver disease, occurs when fat builds up in the liver of people who drink little to no alcohol. The condition can progress to cirrhosis or liver cancer. In the United States, rates have climbed roughly 50 percent over the past three decades and now affect about 38 percent of the population—a trajectory that has made the disease a growing public health concern.

Lihe Liu, a graduate student at the First Affiliated Hospital of Soochow University in Suzhou, China, led the research. She noted the surprise embedded in the results: while sugar-sweetened beverages have long faced scrutiny, their diet alternatives have been marketed as the healthier option. "Our study shows that low- or non-sugar-sweetened beverages were actually linked to a higher risk of metabolic dysfunction-linked steatotic liver disease, even at modest intake levels such as a single can per day," Liu said. She added that diet soda consumption was also tied to a greater risk of dying from liver disease, a finding that directly contradicts the safety narrative these products carry.

The mechanism differs between the two types. Sugary drinks damage the liver by triggering blood sugar spikes, raising insulin levels, and promoting fat accumulation in the organ. Diet sodas, despite their low calorie count, work through a different pathway: they alter the gut microbiome, interfere with the body's sense of fullness, increase cravings for sweet foods, and can even stimulate insulin secretion. Water, by contrast, hydrates the body without triggering any of these metabolic disruptions.

The study's most actionable finding concerns substitution. Replacing either diet or sugary sodas with water reduced the risk of developing fatty liver disease by 13 to 15 percent. Notably, swapping one type of soda for the other—diet for regular or vice versa—provided no protection. Dr. Sajid Jalil, a clinical associate professor of gastroenterology and hepatology at Stanford University School of Medicine who was not involved in the research, called the study particularly credible. "The study showed that both regular and diet soft drinks may harm the liver over time, while choosing water or unsweetened drinks could help protect it," Jalil said. He emphasized that the research carried more weight than previous studies because of its prospective design, large participant pool, validated diagnostic methods for fatty liver disease, and decade-long follow-up period.

The implications are straightforward but significant. As fatty liver disease emerges as a global health concern, the research suggests that the simplest intervention—replacing soda with water—could meaningfully reduce risk. Liu framed water as the healthiest default beverage precisely because it hydrates without affecting metabolism, supports satiety, and maintains overall metabolic function. The consistency of risk reduction regardless of which sweetened drink is replaced points to a single conclusion: the problem is not the type of soda, but soda itself.