Diet soda versus water for a workout: And the winner is...

Dear Alice,

I know that when working out or doing physical activity, you should drink a fair amount of water. I drink a lot of diet soda (used to drink a lot of regular soda), as much as two liters plus in a day. Is diet soda an okay replacement for water? If not, why?


Dear Thirsty,

H2-Oh, what an excellent question! Staying hydrated while you’re physically active is vital for a body in motion. Put simply, water is the most hydrating option available and helps the body restore itself after processes such as breaking down foods, breathing, sweating, and removing waste. While diet soda may boast zero calories and zero sugar, it doesn’t hydrate as well as water, and it increases the risk for a number of health issues including insomnia, tooth enamel erosion, and dizziness. Soaking up the following information will highlight why diet soda doesn’t bring the same benefits as good old water.

Although it contains zero calories and zero sugar, diet soda contains plenty of other ingredients that can affect the body. Preliminary studies have shown tooth enamel erosion, glucose intolerance, and kidney disease to be associated with diet soda consumption, but further research is needed. A number of diet sodas use artificial sweeteners; the Food and Drug Administration has concluded that aspartame, a common artificial sweetener, is safe for consumption, but it’s also been linked to a number of side effects such as dizziness, migraines, memory loss, diarrhea, and mood swings. Ever feel a buzz from diet soda that water doesn't provide? Some sodas contain caffeine, which has mild diuretic properties and increases urination. This decreases the amount of water available to the body — which is counterproductive if you’re trying to quench your thirst. You may also want to note that it has been used as an ergogenic aid to boost athletic performance. When deciding what to consume, weighing out the pros and cons can help you determine what’s best for you to drink.

There are some people who turn to diet soda to help them lose weight. However, these beverages aren’t a cure for losing weight and may in fact be tied to eating more food. In one study, overweight adults who drank diet soda ingested more calories of solid food than other overweight adults who consumed drinks with sugar. There’s also evidence linking artificial sweeteners to higher levels of calorie consumption. While both diet soda and water have zero calories, water doesn't have the artificial sweeteners that have been associated with increased calorie intake.

The bottom line is that water is that whether being physically active or not, consuming water will help keep the body more hydrated than diet soda. Plus, decreasing diet soda consumption may reduce risk for many of the health concerns associated with drinking soda. If you’re interested in drinking more water but don’t want to give up the flavor, you might consider trying substitutes like sparkling water or fruit-infused water. Reducing those two liters to a glass or so may help your body feel even better after your workout. Want to know more about hydrating during physical activity? Check out What to drink before, during, and after physical activity in the Go Ask Alice! Nutrition & Physical Activity archives for more information about what to drink when!

Last updated Dec 22, 2017
Originally published Sep 27, 1996

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