Arguably one of the most confusing debates in the world of health and nutrition right now is the question of which is better: regular soda or diet soda. Regular soda is loaded with added sugars, sometimes upwards of 50 or 60 grams in one bottle, and research shows that over time, consuming an excess of added sugar can lead to weight gain, heart disease, liver disease, kidney disease, diabetes, and even certain cancers. On the other hand, even though diet soda contains no calories or added sugars, recent research has also shown the possibility of weight gain and an increased risk of cancer with this beverage, too.
When looking at the effects of drinking diet soda every day, the conversation gets even more confusing. Some studies have found that zero-sugar sodas could actually help with weight loss, while others have found that it can lead to weight gain. Another study suggested there could be a connection between diet soda and increased mortality rates, but some experts have questioned these findings, pointing out that while it could be the drinks that caused this correlation, the participants’ lifestyles may have been a factor, too.
And then you have the most recent news on diet sodas—namely, the World Health Organization’s announcement in July 2023 that the main zero-calorie sweetener used in Diet Coke and many other diet sodas, aspartame, may cause cancer. The revelation left many health experts and companies divided on the issue.
So, what really happens to your body when you drink diet soda every day? We spoke to registered dietitians and reviewed the most current research on the topic in an effort to better understand the answer. Keep reading to discover seven side effects of drinking diet soda every day.
If your diet soda of choice is Diet Coke, you may already be familiar with its main sweetener—aspartame. This zero-calorie sweetener is found in Diet Coke, Sprite Zero, Coke Zero, and Fanta Zero, as well as some varieties of Crystal Light and certain sugar-free gums.
People have had their concerns regarding the potential “cancer-causing” qualities of aspartame for a while now, but as mentioned above, in July 2023 the debate resurfaced after the World Health Organization (WHO) officially labeled this sweetener as “possibly carcinogenic.” What does that mean, exactly? According to the International Agency for Research on Cancer (IARC), one of the two WHO committees behind the decision, when something is given this label it doesn’t automatically mean that it “causes cancer,” per se. Instead, it means that there are possible connections, but that the research on humans is still too limited to conclude it is cancer-causing. So where does that leave us? Well, regardless of whether aspartame definitively causes cancer, there are a variety of other reasons to consider limiting your intake of diet soda—and we’ll get to some of them below.
Drinking diet soda instead of regular versions is linked to a reduction in body weight, body mass index, and percentage of body fat, especially among the obese, according to data published in JAMA Network Open. Another study in the journal Obesity found that people who drank 24 ounces of diet soda daily for a year maintained a weight loss of up to 16 pounds.
Registered dietitian Toby Amidor, MS, RD, CDN, FAND adds that according to the 2020-2025 Dietary Guidelines for Americans, “Short-term research shows that zero and low-calorie sweeteners are helpful for weight loss, but long-term effects are still inconclusive.” Losing weight sounds good, but that leads us to the flipside of this coin…
A systematic review and meta-analysis in 2017 linked both sugar-sweetened and artificially sweetened beverages to weight gain. Other data suggest that non-nutritive sweeteners may stimulate appetite, leading to weight gain over time. “But much of the data is observational in nature,” says registered dietitian nutritionist Lauren Manaker, MS, RDN, LDN. “Therefore, more studies are needed before we make a definitive connection.”
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“Artificial sweeteners are digested differently than natural sugar,” explains Justine Rosado, RDN, a registered dietitian nutritionist and certified diabetes care and education specialist with The Nutrition Queens. “What determines their metabolic fate is their complex composition, with some completely bypassing the typical absorption and digestion phases that calorie-containing foods undergo.”
The bottom line is that the research is inconclusive. “Most studies show that artificial sweeteners have varying impacts on weight control, though in large part they do not cause individuals to lose or gain weight,” Rosado says.
Though this isn’t necessarily good or bad, most people who drink soda regularly can confirm that there’s a distinctly different taste between regular and diet soda. Artificial sweeteners like aspartame (Equal), Saccharin (Sweet’N Lo), and Sucralose (Splenda) will likely taste noticeably different if you’re used to regular soda. Some nonnutritive sweeteners can be 180 to 13,000 times sweeter than sugar and may change taste preferences over time, according to research in The Permanente Journal.
“Unlike drinking regular soda that is loaded with added sugars, diet soda consumption shouldn’t cause a blood sugar spike,” says Manaker. People who have diabetes but like soda may find diet soda to be a good option.” When consumed in moderate amounts, diet sodas are a safe way to enjoy a sweet-tasting beverage while keeping blood sugars stable,” says Rosado.
“Soft drink consumption, regardless of whether it is diet or sugar-sweetened, may have adverse effects on bone mineral density,” says Manaker. “But the studies show mixed results; dark sodas, in particular, seem to pose the most risk.” Excessive intake of phosphoric acid in sodas creates imbalances in mineral ratios that are linked to osteoporosis and fractures, according to a 2020 report in Nutrients.
“Many diet sodas contain caffeine, which can give people a boost when they are feeling sluggish,” says Manaker. “Unfortunately, if you drink these caffeinated sodas late in the day, you may have trouble sleeping thanks to the stimulation.”
A previous version of this story was published on August 18, 2022. It has been updated to include additional copy and proofreading revisions, additional research, and updated contextual links.
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