The science is clear when it comes to the ill effects of too many added sugars in our diets — but what about zero-calorie sweeteners like those found in diet sodas?
Ongoing research on the sugar alternatives used to sweeten diet beverages has muddied the waters, leaving us all wondering whether diet soda is really as innocuous as we previously thought.
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To set the record straight, we asked registered dietitians to shed light on what really happens to your body when you drink diet soda daily.
Your Gut Health May Take a Hit
"Consumption of any carbonated beverage, including soda, can cause stomach irritation, along with bloating and heartburn," says Amanda Wahlstedt, RDN, a registered dietitian and founder of the private practice Roots to Leaves.
"This is one of the many reasons why soda consumption can be particularly problematic for those with GERD or irritable bowel syndrome."
The non-nutritive sweeteners (NNS) found in diet sodas may also alter the makeup of the gut microbiome, the trillions of microbes that live in the GI tract. Regular intake of NNS like saccharin and sucralose has been linked to dysbiosis, or an imbalance of bacteria in the gut, per a January 2019 review in Advances in Nutrition.
Interestingly, the same study reported that aspartame, the primary NNS found in beverages like Diet Coke and Sprite Zero, may be less likely to alter the gut microbiome due to its rapid breakdown in the small intestine.
Yet other studies conducted in animals have reported that even low doses of aspartame may increase the concentration of bacteria like Enterobacteriaceae — which includes pathogenic bugs like Salmonella and E. coli — in the gut.
How drinking too much diet soda influences gut health is not entirely understood just yet. And experts point out that whether these study findings are even meaningful remains to be seen.
"The main limitation of these studies is that it is not known if the observed changes [to the gut microbiome] are actually bad and if these changes have any clinical relevance," says Paula Doebrich, MPH, RD, registered dietitian and founder of the private practice Happea Nutrition.
"In many studies, people do not consume sweeteners as frequently pre-trial, so changes to the microbiome are to be expected. We also need to know more about what constitutes a 'good' microbiome in order to draw recommendations from the current body of evidence."
Good to Know
The caffeine in diet soda can also stimulate peristalsis, or contractions of the intestinal muscles that promote bowel movements, Wahlstedt says. “This, combined with the NNS found in diet soda, can be a recipe for GI chaos [in sensitive individuals].”
You Might Lose Weight
Swapping regular soda for diet soda can promote weight loss by reducing caloric intake. For example: If you typically sip a 16-ounce Coca-Cola every day, you'll cut out more than 1,300 calories a week by switching to Diet Coke instead.
But because not all calories are created equal, it's not guaranteed that opting for diet soda will deliver lasting weight loss. That's because the NNS found in diet sodas can influence blood sugar management as well as taste preferences, both of which affect weight. (More on each of these topics below.)
It Could Affect Your Heart Health
Cracking open a can of the diet stuff daily isn't great news for your ticker. Researchers observed that people who drank the most artificially sweetened beverages (think: more than two per day) were significantly more likely to develop heart disease or have a stroke compared to those who rarely or never had the drinks, according to a February 2019 study in Stroke, a journal of the American Heart Association.
A comprehensive April 2022 meta-analysis by the World Health Organization also supports this association, with findings from prospective cohort studies showing that regularly having zero-sugar drinks is associated with a 19 percent greater risk of heart disease-related mortality.
It bears noting that these studies were observational, meaning they can only show association, not causation. More clinical research is needed in order to determine cause and effect.
Your Pancreas May Get Confused
Whether you gulp down a glass of regular soda or the calorie-free version, your body may not actually know the difference — at least at first.
"Artificial sweeteners confuse our brains and bodies to some extent," says Nicole Avena, PhD, a neuroscientist and the author of Why Diets Fail (Because You're Addicted to Sugar).
"When we taste something sweet, our body and brain react by releasing insulin in expectation of the glucose that circulates in our blood as a result of eating something with sugar. But when we consume an artificial sweetener, we end up releasing insulin when it isn't necessary, since the sweeteners don't impact blood glucose in the way that caloric sweeteners can."
The problem? This can lead to an excess of insulin (which is produced by the pancreas) circulating in the body. That excess can cause cells to become resistant to insulin, creating issues with blood sugar regulation and increasing one's risk of developing type 2 diabetes over time.
Indeed, people who drank diet soda every day were found to have a 67 percent greater relative risk of developing type 2 diabetes compared to people who did not drink diet soda, per a January 2009 observational study in Diabetes Care.
Again, observational studies cannot establish causation. Still, current research seems to suggest a potential association between greater diet soda intake and conditions of glucose dysregulation.
Your Sugar Cravings Could Spike
On one hand, replacing regular soda with diet soda can be helpful for battling feelings of restriction. "Diet soda can be a great alternative for people who usually consume regular soda, as it can be an easy way to wean yourself off of sugar-sweetened beverages (SSBs) without depriving yourself of the taste," Doebrich says.
But because aspartame tastes 200 times sweeter than table sugar, per the U.S. Food and Drug Administration (FDA), some worry that drinking diet soda daily could actually set us up for more sugar cravings.
"There is some evidence suggesting that artificial sweeteners can actually alter our taste buds, making us more inclined to reach for high-sugar foods," Wahlstedt says. "Since NNS tend to be much sweeter than table sugar, there is a concern that they may overstimulate our sugar-based taste receptors and make naturally sweet foods, like fruit, less appealing."
The bottom line: Diet soda, in moderation, can be a solid choice for those looking to break up with SSBs. But if drinking diet soda leads you to gravitate towards hyper-palatable, ultra-sweet products, it might just negate the supposed benefits (such as blood sugar control and weight management) of choosing a zero-calorie beverage.
What to Drink Instead
"Simple is better," says Wahlstedt, who recommends minimizing soft drinks and diet sodas and instead opting for DIY fizzy drinks. Here are a few options:
- Sparkling water with fresh herbs (such as mint or basil) and fresh-cut fruit or veggies (like cucumber) added
- "My favorite combination is lemon juice, sliced ginger and a little bit of honey in sparkling water for a homemade ginger ale," says Wahlstedt.
- Add a splash of orange or cherry juice to sparkling water
- Buy naturally sweetened fizzy beverages such as Spindrift seltzers or Sound sparkling teas
What About These New 'Healthy' Soda Alternatives?
“Many of the trending prebiotic sodas have added sugars; and while they are marketed as natural, they are still sugar,” Doebrich says. “Prebiotic sodas typically contain ingredients that can lead to gastrointestinal distress in some people.” Those include ingredients like inulin-rich chicory root and Jerusalem artichoke, which may bring on bloat in folks sensitive to high-FODMAP foods.
When it comes to diet soda, the old adage "everything in moderation" applies.
Given the conflicting research findings around the health effects of artificial sweeteners, it's probably best to proceed with caution. But don't sweat it if you can't pass up the occasional diet ginger ale.
"I usually try to wean clients off of diet sodas by introducing healthier alternatives, such as flavored water," Doebrich says. "However, zero-calorie beverages can be part of a healthy lifestyle — and having a Diet Coke here and there is a healthier habit than having a glass of wine or a cocktail, so I never make diet soda a taboo topic with my clients."
- Advances in Nutrition: "Effects of Sweeteners on the Gut Microbiota: A Review of Experimental Studies and Clinical Trials"
- World Health Organization: "Health Effects of the Use of Non-Sugar Sweeteners: A Systematic Review and Meta-Analysis"
- Diabetes Care: "Diet Soda Intake and Risk of Incident Metabolic Syndrome and Type 2 Diabetes in the Multi-Ethnic Study of Atherosclerosis (MESA)*"