Can Diet Coke Cause Fluid Retention?

Diet Coke is an easy way to get your sweetness fix without overloading on sugar, but does that mean it's healthy? Maybe you're feeling bloated lately or you have gained weight instead of lost it. If you've heard bad things about artificial sweeteners, you might wonder if your diet soda is to blame.

Diet Coke contains caffeine, which can cause fluid retention. (Image: kasia2003/iStock/GettyImages)


Diet Coke might not be the best option for weight loss, but there's no evidence to show it can cause fluid retention.

Understanding Fluid Retention

The Mayo Clinic notes that medical term for puffiness — specifically in hands, arms, feet, legs and ankles — is edema, a condition characterized by retention of excess fluid trapped in body tissues. So does this mean you can blame diet soda for your bloated face? Probably not. Many people assume that artificial sweeteners, caffeine and carbonation can cause swelling, but most of the evidence points to Diet Coke being harmless overall (though it isn't as healthy as plain water).

What’s In Diet Coke?

Just because Diet Coke has zero calories per serving, that doesn't mean it's healthy. A few highlights of what's in diet soda usually include:

Aspartame: Instead of sugar, Diet Coke is sweetened with aspartame, an alternative nutritive sweetener that yields only a discretionary number of calories, because your body doesn't break down the aspartame the same way it does sugar.

Although you might have heard about its alleged dangers, there's no indication of a link between aspartame and edema. Aspartame has been approved by the U.S. Food & Drug Administration since 1981 and has been deemed safe by more than 100 studies.

Caffeine: You might blame your fluid retention on caffeine. After all, there's a misconception out there that caffeine makes you dehydrated so your body tries to retain as much fluid as it can to make up for what it's lost. But that's not the case: Diuretics actually help reduce swelling and bloating, according to Heart & Stroke of Canada. Furthermore, Diet Coke has only 46 milligrams of caffeine per 12-ounce serving, and most healthy adults can consume up to 400 milligrams of caffeine a day.

More important, however, it may be a misconception that caffeine dehydrates you. According to Dr. Beth Kitchin, assistant professor of nutrition sciences at the University of Alabama at Birmingham, in a 2014 interview with UAB News, caffeinated beverages don't dehydrate you, and diet soda can even serve as a hydrating alternative for those who don't like plain water.

Contrary to popular belief, caffeine and fluid retention have no correlation. Fluid retention has many recognized causes, but caffeine consumption isn't one of them.

Sodium: A common cause of edema is eating too much salty food, but even though Diet Coke does contain sodium, it is only 40 milligrams per 12-ounce serving. The Dietary Guidelines for Americans, 2015-2020, recommends an upper level of 2,300 mg of sodium per day. Unless you're consuming more than 57 cans of diet soda a day, it is unlikely that your Diet Coke habit is to blame for edema.

Carbonation: Soda gets its signature fizziness from dissolved carbon dioxide. Consuming so many bubbles might make you feel a little gassy, but the carbonation will not dehydrate your body — in fact, carbonated drinks are just as hydrating as water.

Losing Weight With Diet Soda

Even if Diet Coke is unrelated to bloating and puffiness, that doesn't necessarily mean it will help you lose weight. On the contrary, studies have shown that consumption of Diet Coke can actually cause you to gain weight.

In an study published in the July 2017 issue of the Canadian Medical Association Journal, the researchers found that consuming nonnutritive sweeteners causes weight gain and related conditions like metabolic syndrome and Type 2 diabetes.

Just because it's free of sugar doesn't mean that Diet Coke is a healthy free-for-all, but it's likely not a cause of edema. Take a look at other aspects of your diet, and if your bloating doesn't go away, consider other ways of reducing water retention.

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