Diet Coke might seem like a smart swap if you're cutting sugar, but recent studies suggest it could do more harm than you think. Just one can a day is enough to raise red flags in some key areas of your health, from your brain to your liver.

While the research doesn't always show clear-cut causes, the connections are strong enough to get your attention.

Here's what that daily can of Diet Coke could be doing to you:

Diet Coke Might Speed Up Brain Aging

A 2025 study in Neurology tracked how artificial sweeteners affect the brain. The people who drank one Diet Coke a day showed signs of faster cognitive decline. We are talking about the kind of mental slip you would expect from someone a year and a half older than their real age.

And this wasn’t just forgetting where you parked. The biggest impacts hit memory and language skills. That is especially concerning if you are under 60 or living with diabetes.

Qingyu / Unsplash / Latest study finds that consuming the amount of artificial sweeteners in about one can of diet soda per day is linked to a faster rate of cognitive decline.

The study found these groups felt the biggest hits. Your brain is basically doing overtime trying to adjust, and that slow wear and tear adds up.

It Could Mess With Your Metabolism

Diet Coke isn’t free from metabolic baggage. A big 2025 study showed that people who drank one can a day were 67% more likely to develop type 2 diabetes over time. That is a steep jump for something that is sugar-free.

Researchers think it is partly because artificial sweeteners confuse the body’s insulin response. Your body tastes sweet, gets ready for sugar, but it never comes. Over time, this disconnect could raise your blood sugar and mess with how your body stores fat.

Your Liver Doesn’t Love It!

Liver health isn’t the first thing most people think about when cracking open a can of Diet Coke. But it should be. New findings from 2025 link just one daily diet soda to a 60% higher risk of developing MASLD, a serious liver disease tied to fat buildup.

That risk is even higher than with regular soda.

That means your go-to diet drink might not be doing your liver any favors. Over time, this condition can turn into scarring or cirrhosis, which are major problems. The lead researcher put it simply: Diet sodas are not the “safe” option many people think they are.

It Might Throw Off Your Gut

Your gut is full of bacteria that help break down food and keep your immune system strong. Some research hints that the sweeteners in Diet Coke, like aspartame, could throw that balance out of whack. That could lead to bloating, poor digestion, or even immune issues.

Kenny / Unsplash / Studies suggest that sweeteners in Diet Coke can sabotage your gut health.

To be fair, most of these studies have been done on animals, and human data is still growing. But the early signs aren’t promising. One thing is clear: your gut doesn’t process fake sweeteners the same way it does real food.

It Can Wreck Your Teeth

Even without sugar, Diet Coke still packs acid. And that acid doesn’t sit quietly. Studies show it can wear down your enamel just like regular soda. Once enamel is gone, it doesn’t grow back. That opens the door to cavities, tooth sensitivity, and a whole lot of dental bills.

This damage doesn’t take years, either. If you sip diet soda daily, and especially if you drink it slowly or swish it around, your teeth stay bathed in acid. Dentists can spot the damage early, even if you don’t feel it yet.