The research showed that neither sugary drinks nor diet/artificially sweetened beverages are safe for the liver. In fact, the study found that diet drinks pose an even higher risk for developing metabolic dysfunction–associated steatotic liver disease (MASLD) than sugary ones. Even a single can of diet soda per day significantly increases the risk.
In the UK Biobank study involving more than 120,000 participants, drinking more than one serving of diet beverages daily increased the likelihood of developing MASLD by 60%, and the risk of severe liver problems was also 55% higher. Sugary drinks are also harmful, but their associated risk was around 50%, and they did not show a clear link to severe liver-related outcomes.
Researchers also observed that both beverage types increase liver fat content: sugary drinks by about 5%, and diet drinks by 7% compared with people who did not consume them at all.
The mechanisms differ:
- Sugary drinks cause rapid spikes in blood glucose and insulin, promote weight gain, and increase uric acid levels — all of which contribute to liver fat buildup.
- Diet drinks may disrupt the gut microbiome, weaken satiety signals, increase cravings for sweets, and may even trigger insulin responses, all of which are unfavorable for liver health.
One of the key messages of the study is that drinking water significantly reduces risk: replacing sugary drinks with water lowers MASLD risk by 12.8%, and replacing diet drinks reduces it by 15.2%.
Experts agree that until more mechanistic research is available, the safest choice is clearly water, as it contains neither sugar nor artificial sweeteners and does not burden the liver.
