For decades, we've been told to replace sugary drinks with diet drinks. Zero calories, zero guilt. But a new study presented at the UEG Week 2025 Berlin turns everything on its head: those who consume more than 250 grams a day of drinks with artificial sweeteners has a 60% higher risk of developing fatty liver. Worse, diet drinks are also linked to liver disease mortality, while sugary drinks are not.
The study followed 123.788 British adults for over ten years, analyzing every can, every sip. Hold back the facile comments: the results are unequivocal.
Diet soda: just one can a day can damage your liver.
The research team led by Lihe Liu ofManchester University used repeated food questionnaires every 24 hours to accurately track beverage consumption. The participants, all without signs of liver disease at the start of the study, were followed for a median of 10,3 years.
During this time, 1.178 people developed MASLD (metabolic fatty liver disease) and 108 died from liver-related causes.
Data shows that diet or low-sugar drinks increase the risk of fatty liver disease by 60% (HR: 1.599), while traditional sugary drinks they stop at 50% (HR: 1.469). As presented at the 2025 National Astronomy Meeting of Royal Astronomical Society, both types are also associated with higher levels of liver fat. The paradox is complete: the solution designed to avoid the damage of sugar turns out to be more dangerous.
MASLD, formerly known as nonalcoholic fatty liver disease (NAFLD), occurs when excess fat accumulates in the liver. Over time, this can trigger inflammation and lead to symptoms such as abdominal pain, fatigue, and loss of appetite.
Today, it is the most common chronic liver disease in the world, affecting over 30% of the population and is rapidly becoming a leading cause of liver-related death.
Why sweeteners betray the liver
The biological mechanism behind this effect is subtle. As he explains Lihe Liu"The high sugar content in traditional beverages causes rapid spikes in blood glucose and insulin, promotes weight gain, and increases uric acid levels, all of which contribute to the accumulation of fat in the liver." So far, nothing new. But artificial sweeteners aren't as harmless as they seem.
Le diet drinks They can harm liver health by altering the gut microbiome, disrupting the perception of satiety, stimulating sweet cravings, and even inducing insulin secretion. A recent study published in Nature Metabolism has shown that the sucralose, one of the most common sweeteners, increases blood flow to the hypothalamus (the part of the brain that regulates appetite) by 3%, making you three times more hungry than sugary drinks. It's like a false friend that promises to help you while sabotaging your metabolic efforts.
Water is the only real alternative
The researchers also analyzed what happens when these beverages are replaced with water. The results are clear: replacing diet sodas with water reduces the risk of MASLD by 15,2%, while replacing sugary drinks leads to a 12,8% reduction. Switching between sweetened beverages, however, does not offer any risk reduction.
"The safest approach is to limit both sugary and artificially sweetened beverages," Liu emphasizes. "Water remains the best choice because it removes the metabolic burden and prevents fat accumulation in the liver, hydrating the body." A simple concept, yet forgotten among the shelves full of colorful cans that promise miracles without consequences.
The most disturbing fact? As we have already documented for other sweetenersErythritol can increase the risk of heart attack and stroke by enhancing platelet activity. Sucralose damages DNA. And now we're finding that diet sodas as a whole also affect the liver, with a direct correlation to liver disease mortality that traditional sugary drinks don't.
Diet drinks: we need to rethink the guidelines.
The study is part of a broader prevention strategy targeting not only liver disease but also cardiorenal and metabolic health. The researchers now intend to further explore the causal mechanisms through long-term randomized trials and genetic analyses, with a particular focus on how sugar and sweeteners interact with the gut microbiome.
The question is no longer whether artificial sweeteners are harmful, but how much harm they cause and to whom. Evidence is mounting: they alter blood sugar levels, predispose to type 2 diabetes, alter the gut microbiota, and we now know they significantly increase the risk of fatty liver disease and death from liver disease.
Diet sodas aren't the health shortcut we thought. They're a metabolic dead end that our bodies pay for with interest.
