Sugary and Diet Beverages Both Tied to Liver Damage, Researchers Find
A new study has found that drinking even one can of diet soda a day may sharply raise the risk of developing nonalcoholic fatty liver disease, a growing condition that already affects nearly 40% of adults in the United States.
Researchers reported that participants who regularly consumed low or no-sugar soft drinks faced a 60% higher risk of liver fat buildup compared with non-drinkers. In comparison, those who opted for sugary beverages had a 50% higher risk. The findings challenge long-held assumptions that diet sodas are a healthier alternative.
“Sugar-sweetened beverages (SSBs) have long been under scrutiny, while their ‘diet’ counterparts have enjoyed a reputation as the better choice,” said lead author Lihe Liu, a graduate student in the department of gastroenterology at the First Affiliated Hospital of Soochow University in Suzhou, China.
The research, which has not yet been published in a peer-reviewed journal, was presented Monday in Berlin at the United European Gastroenterology Week, an annual meeting of digestive health specialists.
Nonalcoholic fatty liver disease, or NAFLD, occurs when fat accumulates in the liver despite little or no alcohol use. The condition, now increasingly referred to as metabolic dysfunction–associated steatotic liver disease (MASLD), can lead to inflammation, scarring (cirrhosis), and even liver cancer.
“Our study shows that LNSSBs (low or non-sugar-sweetened beverages) were actually linked to a higher risk of MASLD, even at modest intake levels such as a single can per day.”
The damage mirrors what doctors often see in heavy drinkers, but in this case, diet and lifestyle are to blame. Over the past three decades, NAFLD rates have surged by around 50% in the U.S., with nearly 38% of Americans now living with the disease. Globally, researchers say, MASLD has become a major driver of liver transplants and cancer cases.
“These findings challenge the common perception that these drinks are harmless and highlight the need to reconsider their role in diet and liver health, especially as MASLD emerges as a global health concern.”
The study followed nearly 124,000 adults without liver disease who were part of the UK Biobank, a large-scale biomedical database that tracks participants’ health and lifestyle habits over time. Over roughly ten years, researchers collected detailed 24-hour dietary questionnaires to track beverage consumption patterns.
Results showed that both regular and diet soft drinks were linked to higher rates of MASLD and liver-related death. However, participants who replaced either type of sweetened beverage with water saw a significant drop in risk, with reductions of nearly 13% for sugary drinks and 15% for diet drinks.
Switching between sugary and diet sodas made no difference. The only meaningful protective factor was water.
The study offers “direct evidence of dietary behaviors influencing MASLD,” said Dr. Sajid Jalil, a clinical associate professor of gastroenterology and hepatology at Stanford University School of Medicine, who was not involved in the research.
“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. For me, this study has a lot more weight than previous studies because of its prospective design, involving a large number of subjects, a validated test for the diagnosis of MASLD and a long follow-up.”
The study also sheds light on how these drinks may damage the liver through different biological pathways.
Sugary beverages, packed with high-fructose corn syrup or refined sugars, cause sharp spikes in blood glucose and insulin. Over time, this can lead to insulin resistance, weight gain, and fat accumulation in the liver.
“They can change the gut microbiome, interfere with feelings of fullness, increase preference for sweet foods and even stimulate insulin secretion,” Liu told CNN in an email.
“Water, however, hydrates the body without affecting metabolism, helps with satiety and supports overall metabolic function. That’s why the risk reduction is similar no matter which sweetened drink is replaced — it shows that water is the healthiest default beverage.”
While the findings have not yet undergone peer review, experts say they add to a growing body of evidence linking beverage habits to long-term liver health. As NAFLD and MASLD become more prevalent, particularly in younger adults, researchers are urging public health authorities to focus not just on sugar consumption, but also on the widespread reliance on “zero-calorie” alternatives.
The message, researchers say, is clear. There’s no truly safe soda. Whether sweetened with sugar or artificial substitutes, both appear to take a toll on the liver, and the simplest fix might already be in your glass.
Moumita Basuroychowdhury is a Contributing Reporter at The National Digest. After earning an economics degree at Cornell University, she moved to NYC to pursue her MFA in creative writing. She enjoys reporting on science, business and culture news. You can reach her at moumita.b@thenationaldigest.com.
