Is Soda Bad for Fatty Liver? Regular vs. Diet Soda

TL;DR

• Sugary soda is bad for fatty liver. A 12-ounce can of cola has about 37 g of sugar, most of it fructose, and the European liver guideline says to avoid sugar-sweetened drinks.
• The evidence is strong. In a six-month trial, a liter of regular cola a day raised liver fat far more than the same amount of milk, diet cola or water.
• Diet soda is a better stopgap, but the research on it is mixed. Water, unsweetened tea and coffee are the drinks to aim for.

Yes, regular soda is bad for fatty liver. Sugar-sweetened drinks are one of the most consistent dietary risk factors for MASLD (formerly NAFLD), and cutting them is one of the simplest changes with strong evidence behind it.

Diet soda is a harder question. It doesn’t carry the sugar load, and the best trial found it didn’t raise liver fat. But some large observational studies have linked diet drinks to liver disease too, so it’s best treated as a bridge away from sugary soda, not a health drink.

Why is sugary soda so hard on the liver?

The sugar in soda is high-fructose corn syrup or table sugar, and both are roughly half fructose. In USDA data for regular cola, about 22 g of a can’s 37 g of sugar is fructose.

Fructose is handled mostly by the liver, and when there’s more than the liver can burn, it turns the excess into fat, a process called de novo lipogenesis. The AASLD’s 2023 practice guidance puts it plainly: diets with excess calories, particularly from saturated fat, refined carbohydrates and sugar-sweetened beverages, are associated with fatty liver, and excessive fructose in particular increases the risk of fatty liver, inflammation (MASH) and advanced fibrosis independent of calorie intake.

Drinking sugar makes it worse. It goes down fast, and according to the American Heart Association, higher soft drink intake is associated with eating more calories overall and higher body weight. In a Finnish study, three weeks of an extra 1,000 calories a day from simple sugars raised liver fat by 33% and nearly doubled the liver’s fat-making rate.

That is why the NIDDK advises people with fatty liver to avoid foods and drinks with large amounts of simple sugars, especially fructose, which it notes is found in sweetened soft drinks, sports drinks, sweetened tea and juices.

How much sugar is in soda?

Here is what a typical serving contains, from USDA FoodData Central:

Drink	Calories	Sugars	Fructose
Cola, regular (12 fl oz)	155	37 g	22 g
Lemon-lime soda (12 fl oz)	151	38 g	22 g
Orange juice, from concentrate (12 fl oz)	183	31 g	about 16 g
Cola, diet (12 fl oz)	4–7	0 g	0 g
Club soda or sparkling water (12 fl oz)	0	0 g	0 g
Black coffee or unsweetened tea (8 fl oz)	2	0 g	0 g

For context, the World Health Organization recommends keeping free sugars under 10% of daily calories, and ideally under 5%, which is about 25 g (6 teaspoons) a day for an adult. The American Heart Association sets a limit of about 100 calories of added sugar a day for most women (roughly 6 teaspoons) and 150 for most men (roughly 9). One can of cola uses up a whole day’s allowance for most women, and a 20-ounce bottle has about 61 g.

What do studies show about soda and fatty liver?

The evidence against sugary drinks is among the strongest in fatty liver nutrition research, because it includes a controlled trial as well as large cohorts:

• A six-month trial: Danish researchers assigned 47 overweight adults to drink 1 liter a day of regular cola, semi-skimmed milk, diet cola or water. Liver fat rose 132 to 143% more in the regular cola group than in the other three. Diet cola behaved much like water.
• Framingham Heart Study: Among 2,634 adults with liver CT scans, people drinking at least one sugar-sweetened beverage a day had 61% higher odds of fatty liver than non-drinkers. A later analysis that followed participants for six years found that frequent drinkers in the older group had about 2.5 times the odds of developing fatty liver.
• Women’s Health Initiative: In 98,786 postmenopausal women followed for about 21 years, those who drank one or more sugary drinks a day had an 85% higher risk of liver cancer and a 68% higher risk of dying from chronic liver disease than women who had three or fewer a month.
• Cutting sugar quickly lowers liver fat: In 41 children with obesity and high sugar intake, swapping sugar for starch at the same calories for just nine days cut median liver fat from 7.2% to 3.8%. The study had no control group, but the drop was large and fast.

The 2024 European guideline makes this a strong recommendation: adults with MASLD should avoid sugar-sweetened beverages. For other foods on that list, see our guide to foods to avoid with fatty liver.

Is diet soda safe for fatty liver?

The honest answer is that the evidence is mixed.

Reassuring findings:

• In the Danish trial above, a liter a day of aspartame-sweetened diet cola for six months did not raise liver fat compared with water.
• In Framingham, diet soda intake was not associated with fatty liver.
• In the Women’s Health Initiative, drinking artificially sweetened beverages daily was not significantly linked to liver cancer or death from chronic liver disease.

Findings that raise questions:

• A UK Biobank analysis of 123,788 adults presented at UEG Week 2025 found that drinking more than 250 g a day (about 8.5 ounces) of low- or no-sugar drinks was linked to a 60% higher risk of developing MASLD over about 10 years, compared with 50% for sugary drinks. Replacing either with water was linked to lower risk. It was a conference abstract, not yet a peer-reviewed paper.
• A 2025 MRI study of 25,885 adults linked one or more artificially sweetened drinks a day, as well as sugary drinks, to slightly higher liver fat and a higher MRI marker of liver inflammation.

Why the mismatch? Observational studies struggle with reverse causation: people who already have weight or blood sugar problems are more likely to switch to diet drinks. The main trial was small and lasted six months. Separately, the World Health Organization’s 2023 guideline advises against using non-sugar sweeteners to control weight or reduce disease risk. That is a conditional recommendation, and it doesn’t apply to people who already have diabetes.

The practical takeaway: if you drink regular soda every day, switching to diet soda is a real improvement in sugar and calories. Treat it as a stepping stone, and make water, sparkling water and unsweetened drinks your default.

What should you drink instead?

• Water, still or sparkling. Add lemon, lime, cucumber, mint or a few crushed berries for flavor.
• Coffee. The AASLD says 3 or more cups a day, caffeinated or not, could be recommended for people with fatty liver who have no reason to avoid it. See is coffee good for fatty liver.
• Unsweetened tea, hot or iced.
• Milk in normal portions. In the Danish trial, a liter a day of semi-skimmed milk didn’t raise liver fat the way cola did, though it still has calories.

Be wary of drinks that seem healthier than soda but aren’t:

• Fruit juice, even 100% juice. The WHO counts its sugar as free sugar, and the European guideline recommends fruit, not juice. Whole fruit is a different matter; see is fruit bad for fatty liver.
• Sweet tea, sports drinks, sugary energy drinks and sweetened coffee drinks, which are sugar-sweetened beverages under another name.
• Tea sweetened with honey. Honey is still added sugar, as our guide to honey and fatty liver explains.

How to cut back on soda

• Step down, don’t stop cold if that feels impossible: a smaller size, then half soda and half sparkling water, then diet or unsweetened sparkling water.
• Don’t keep it at home. Buy it by the can when you really want one, not by the case.
• Order water with meals out, and skip the free refills.
• Replace the ritual. If the afternoon soda is really a break, make it coffee, tea or a walk.
• Track what you drink. Drinks are easy to forget. An app like Liverly logs added sugar from drinks along with food, so a daily soda shows up in your numbers.

The Bottom Line

Sugary soda is bad for fatty liver, and the evidence is some of the strongest in nutrition for liver health: a controlled trial showing more liver fat within six months, large studies linking daily soda to fatty liver, liver cancer and liver-related death, and a guideline recommendation to avoid it. Cutting it is one of the clearest wins available.

Diet soda is a better choice than regular, and the best trial evidence found no rise in liver fat, but some large observational studies have raised concerns. Use it as a bridge if you need one, and aim for water, unsweetened tea and coffee. For how drinks fit into your overall eating, see the fatty liver diet.

Sources

• Maersk M, et al. Sucrose-sweetened beverages increase fat storage in the liver, muscle, and visceral fat depot: a 6-mo randomized intervention study. Am J Clin Nutr. 2012.
• Ma J, et al. Sugar-sweetened beverage, diet soda, and fatty liver disease in the Framingham Heart Study cohorts. J Hepatol. 2015.
• Zhao L, et al. Sugar-Sweetened and Artificially Sweetened Beverages and Risk of Liver Cancer and Chronic Liver Disease Mortality. JAMA. 2023.
• United European Gastroenterology: Artificially sweetened and sugary drinks are both associated with an increased risk of liver disease (UEG Week 2025).
• EASL–EASD–EASO Clinical Practice Guidelines on the management of MASLD: Executive Summary. 2024.

This article is for informational purposes only and is not medical advice. Talk to your doctor or hepatologist about your specific situation.