Updated on October 18, 2023.
On any given day, around 20 percent of people in the United States drink diet soda, according to the latest available data from the Centers for Disease Control and Prevention (CDC). Some even swear they’re addicted to the stuff. But rumors abound about diet soda’s health effects, some blatantly false and some surprisingly true. Can you separate fact from fiction?
1. People have grown deathly ill from drinking cans of soda with dirty tops.
Myth. Legend has it that the lethal hantavirus spreads to humans when they drink soda contaminated by the droppings of warehouse rats or mice. True, humans can catch the hantavirus from rodent saliva, urine, or droppings, but there are no known cases of a person getting it from unclean diet soda cans, or any food packaging. This is because metal food and drink containers that seal tightly, like soda cans, are resistant to rodents. Still, it's a good idea to wipe any icky stuff off the top before opening.
2. Diet soda is 99 percent water.
Fact. Though it contains caffeine, natural flavorings, and sugar substitutes such as aspartame or sucralose, diet soda is mainly carbonated water. In fact, one 2007 advertisement for a major beverage brand actually bragged about this, the idea being that any beverage consisting mostly of water can’t be bad for you. That part isn’t true, though—the other 1 percent can potentially affect your health, depending on the contents.
3. An artificial sweetener commonly used in diet soda recipes was developed as an ant poison and is therefore hazardous.
Myth. Aspartame was created in 1965 by a chemist working on an ulcer drug. The compound doesn't kill ants or short-circuit their nervous systems, as legend has it. But even if those things were true, they wouldn't prove that aspartame is dangerous to humans. Many foods that are fit for human consumption—like black pepper, cinnamon, star anise, and turmeric—can also repel ants and other insects.
4. Drinking diet soda while eating Mentos candies can create a mildly explosive reaction in your body.
Mostly myth. You may have seen social media videos of people creating mini-geysers by combining the two products. It works because certain types of Mentos have a microscopically rough surface that creates bubbles when mixed with the carbon dioxide in diet soda. Pressure builds quickly and an eruption occurs, often within seconds. In humans, consuming both products at the same time may cause a mild reaction—like burping—but not a major internal eruption, since pressure is unable to build the same way.
5. Drinking diet soda can cause or worsen multiple sclerosis symptoms.
Myth. The Multiple Sclerosis Foundation has debunked this falsehood, as have the U.S. Food and Drug Administration (FDA) and other health organizations. The notion that diet soda can cause neurological disorders may be based on an observation made years ago by the CDC that in some people, aspartame seemed linked to mild neurological problems, such as headaches and moodiness. However, the CDC found that these symptoms affected most people, not just diet soda drinkers.
6. Diet sodas contain more calories than they show on the label.
Myth. Contrary to internet rumors, diet soda doesn’t contain secret calories, and drink companies don’t get to call their products calorie-free in exchange for paying big fines to the FDA. Legally speaking, drinks can only be labeled as calorie-free if they have fewer than 5 calories per serving; diet colas typically have less than 1 calorie.
7. Diet soda may cause cancer.
Maybe. Arguments about an aspartame-cancer connection have flared for decades. The FDA has consistently held the position that there is no scientific support for safety concerns around aspartame consumption. But in July 2023, the World Health Organization (WHO) and the International Agency for Research on Cancer (IARC) released a statement that it would be adding aspartame to its list of substances that might cause cancer. The change was based on newer research into the sweetener. While that may sound alarming, the WHO and IARC also said that there was no need to change the acceptable daily limit of 40 mg per kilogram of body weight. In other words, an adult weighing 154 pounds would have to drink between 9 and 14 cans of diet soda every day to exceed this limit.
