Is Diet Soda Really Better? What Science Says About Your Liver
I know I’m not the only one who's felt virtuous cracking open a can of diet soda instead of the regular stuff. For years, “zero sugar” drinks have been marketed as the smarter, guilt-free choice—one without the metabolic consequences.
But new research presented at the 2025 United European Gastroenterology (UEG) Week is turning that assumption on its head.
According to the study, drinking as little as one can of soda a day, whether sugar-sweetened or artificially sweetened, was linked to a higher risk of liver disease. Even more surprisingly, diet sodas were associated with a slightly greater risk than their sugary counterparts.
Soda & liver disease
Researchers looked at data from more than 123,000 adults in the UK Biobank who had no signs of liver disease at the start. Over the next decade, participants reported their beverage habits, and researchers tracked who went on to develop metabolic dysfunction–associated steatotic liver disease, or MASLD—a condition that causes fat to accumulate in the liver, even in people who rarely drink alcohol.
The results were sobering. People who drank more than one can of soda a day, whether it was sweetened with sugar or artificial sweeteners, had a much higher risk of developing MASLD.
- Those who drank regular soda had about a 50% greater risk.
- Those who drank diet or “zero-sugar” versions had about a 60% greater risk.
Even more striking, people who drank diet soda regularly were also more likely to die from liver-related causes. And the more they drank, the higher their risk climbed.
This isn’t just about the liver processing sugar or artificial sweeteners. Both types of drinks were linked to greater fat accumulation in the liver, suggesting a broader impact on metabolism and inflammation.
The overlooked impact
Nonalcoholic fatty liver disease, now called MASLD, is one of the most common yet least talked-about health conditions today. Nearly 4 in 10 adults1 in the U.S. have it, and the number keeps rising. It’s often silent at first, but over time, excess liver fat can lead to inflammation, scarring, and even liver cancer.
For years, the spotlight has been on sugar-sweetened drinks as a major contributor, but this new data shows that “diet” versions might not be the escape route we thought. While the study hasn’t been peer-reviewed yet, its scope and follow-up make the findings hard to ignore.
Protect your liver (starting today)
When researchers looked at beverage swaps, they found that replacing a single can of soda (regular or diet) with water lowered liver disease risk by 13 to 15%. That’s one easy daily decision with a measurable payoff for your long-term health.
Beyond hydration, the usual suspects for liver health still hold true:
- Move your body regularly: Strength training and daily movement both help regulate blood sugar and reduce fat accumulation in the liver.
- Eat more fiber: Especially from veggies, legumes, and whole grains to support detox pathways.
- Limit ultra-processed foods, which often sneak in refined oils and added sugars that strain liver function.
- Reduce alcohol intake: Even moderate drinking can strain your liver and contribute to fat buildup and inflammation.
The takeaway
This study doesn’t mean you have to banish every soda forever. What it does remind us is that “sugar-free” doesn’t necessarily mean “risk-free.” Both regular and diet drinks seem to place stress on the liver when consumed often, and over time, that can add up.
Start by swapping one can per day for water and notice how you feel. Your liver works incredibly hard filtering toxins and supporting metabolism, so giving it a break from processing artificial sweeteners or excess sugar is a small change with potentially big benefits.
