Can you drink 1 Diet Coke a day and still be healthy? How to make it work, according to dietitians.

Kristen Hollingshaus doesn’t make a Starbucks run to cure her afternoon slump. Instead, she goes for a frosty Diet Coke she’s made sure to let “marinate” (aka chill in the fridge) for at least two weeks before mixing it with crystallized lime and pebble ice. It’s a decadent, well-honed routine that has earned Hollingshaus the nickname “Diet Coke girl??” and even netted her a paid social media partnership with the Coca-Cola Company. Then there’s cookbook author Kathleen Ashmore, who has her own Diet Coke routine, which includes a wineglass and jarred cherries. And private chef Meredith Hayden doesn’t only save her Diet Coke for the afternoon. Rather, as she shared recently in a “day in my life” TikTok, she starts her morning with the crisp, sugar-free beverage.

Diet Coke is undoubtedly beloved — of the more than $285 billion U.S. soft drink market, it’s the fourth most popular soda in the United States. Yet Diet Coke has long benefited from a “health halo,” meaning it has stayed on the shelves of some of even the most wellness-focused individuals (Hollingshaus, for example, first gained a social media following by recording her daily multi-mile walks on a pad underneath her desk).

The Centers for Disease Control and Prevention (CDC) is pretty clear: Sugar-sweetened beverages are associated with less-healthy behaviors and frequent consumption is linked to “weight gain, obesity, type 2 diabetes, heart disease, kidney diseases, non-alcoholic liver disease, tooth decay and cavities and gout.” Yet the once-daily Diet Coke, which is sweetened with aspartame, is such a pervasive trend — how bad could it be?

What’s actually in Diet Coke?

According to the official Coca-Cola website, Diet Coke contains “carbonated water, caramel color, aspartame, phosphoric acid, potassium benzoate (to protect taste), natural flavors, citric acid and caffeine.” By comparison, original Coke contains high-fructose corn syrup, a type of sugar, in place of the aspartame.

Aspartame, a sugar substitute, is what makes Diet Coke taste sweet. Though aspartame contains four calories per gram, it’s also approximately 200 times sweeter than sugar, meaning much less of it needs to be used. That’s why it’s considered a low-calorie option — Diet Coke’s nutrition label claims the beverage contains zero calories, though in reality it may have a very small amount.

Why is aspartame controversial?

In July 2023, the World Health Organization (WHO) classified aspartame as “possibly carcinogenic” to humans — however, it also said that the results “do not indicate that occasional consumption should pose a risk to most consumers.”

That’s because the WHO’s consumption limit of aspartame was a maximum of 40 milligrams per kilogram of body weight per day. For a 130-pound person, that is equivalent to 12 cans of Diet Coke.

Soon after the announcement, the U.S. Food and Drug Administration (FDA) pushed back, claiming that the WHO caused undue alarm for consumers of aspartame. The FDA noted that the WHO’s findings do not mean that aspartame is “actually linked to cancer.”

“Aspartame is one of the most studied food additives in the human food supply,” the FDA’s website says of the sugar substitute. “FDA scientists do not have safety concerns when aspartame is used under the approved conditions.”

The FDA also pointed out that many people use aspartame-containing products to lower their calorie intake, which can reduce their overall sugar consumption. We know that too much sugar can cause a wide variety of health issues, such as obesity, type 2 diabetes and heart disease.

It’s not just cancer that aspartame has been linked to, though: Dr. Jennie Stanford, an obesity medicine physician and medical contributor for Drugwatch, tells Yahoo Life that aspartame has been linked to other health conditions, such as adverse metabolic effects like weight gain or blood sugar issues and cognitive decline. However, it’s important to note that more research is needed to understand the association — and that just because there is a connection, it does not mean that aspartame directly causes these conditions.

What do experts say about a once-daily Diet Coke habit?

The dietitians I spoke with for this article did not demonize a daily Diet Coke, but noted that it’s important to consider why you’re reaching for that crisp can in the first place.

Dietitian Michelle Routhenstein tells Yahoo Life that she’s a believer in assessing how your habits fit into your overall health goals. Is your Diet Coke habit stopping you from hydrating properly with water? Or, do you drink a Diet Coke daily because you regularly go through the McDonald’s drive-through and always order one to wash down a double cheeseburger? The habits you stack might impact how healthy your daily Diet Coke is overall.

Routhenstein points out that some people use Diet Coke as “a pick-me-up during the day.” While enjoying a soda is OK, Routhenstein notes that it can’t give you the energy that a snack or meal would if what you’re really feeling is hunger.

Dietitian Christine Byrne says she doesn’t see any real health risks with drinking one Diet Coke per day, but agrees that Diet Coke is not a snack, even if you do think of it as a special treat. “When your body needs food, you should eat food,” she tells Yahoo Life. “Don’t try and trick yourself into feeling full by drinking a calorie-free soda!” If you’re replacing food with Diet Coke as a way to curb your hunger, it warrants an evaluation of your overall eating habits.

It’s also important to make sure that your Diet Coke habit isn’t influencing your diet overall. “Some research shows that drinking lots of diet soda, or consuming lots of artificial sweeteners, could actually increase your overall calorie intake, which seems counterintuitive to a lot of people since these drinks are calorie-free,” says Byrne. “The current thinking is that these drinks trick your brain into thinking it’s consuming calories and sugar, and when that turns out not to be the case, it increases cravings for sugary foods.”

There’s also a psychological reason why you may seek out higher-calorie foods after drinking a Diet Coke: If you assume you’re being virtuous with your Diet Coke instead of drinking the original version, you might not think twice about going for something sugary or less nutritious, as a 2012 study suggested.

The bottom line

If you are drinking an entire sleeve of Diet Coke daily, you should cut back. However, a single Diet Coke a day that you enjoy and aren’t replacing real food with can be perfectly fine.

One thing to consider: Make sure your body is as happy as your taste buds. If you experience uncomfortable gas or bloating from the carbonation in Diet Coke, for example, that’s a sign you may want to skip soda in favor of something else, like a noncarbonated sugar-free beverage such as green tea.

There’s also caffeine to factor into the equation. In a 12-ounce can of Diet Coke, there are approximately 46 milligrams of caffeine, compared with about 95 to 200 milligrams in a typical cup of brewed coffee. Drinking any caffeine too late in the day could disrupt your sleep, especially for those who are sensitive to it.

If you do want to cut back on the Diet Coke, for whatever reason, there are options, says Byrne. “If you love the bubbles of diet sodas but want to limit them a bit, try subbing flavored seltzer,” she explains. “There are so many fun flavors on the market these days, or you could try making your own with some plain seltzer and a little bit of juice or tea.”

Trying to cut back on bubbles completely? Go for a splash of juice in plain water instead — or even fresh fruit, like oranges, lemons or cucumbers. After all, it’s often a ritual that makes a beverage habit so special — and recreating it with a different drink may offer some of the same effects.