Is Diet Soda Considered Water? The Complete Hydration Guide

December 2, 2025 •

3 min read

According to reports referenced by PepsiCo, diet soft drinks can be up to 99 percent water, which means they do technically contribute to your fluid intake. However, this leads many to wonder if diet soda is considered water and a healthy substitute for it.

Quick Summary

Diet soda is composed primarily of water, which aids fluid intake, but it is not a direct nutritional substitute for plain water due to its artificial sweeteners and acids.

Key Points

Primarily Water: Diet soda is composed of mostly water, with some versions containing as much as 99%, allowing it to contribute to your total fluid intake.
Not a Substitute: Due to its other ingredients, diet soda is not considered a nutritionally equal substitute for plain water for optimal hydration.
Contains Additives: The beverage contains artificial sweeteners, flavorings, and acids that are absent in pure water.
Dental Health Risk: The acids in diet soda can lead to tooth enamel erosion over time, unlike plain water, which is good for dental health.
Mild Diuretic: Some diet sodas contain caffeine, which has a mild diuretic effect, though this effect is not significant enough to cause dehydration from moderate consumption.
Healthier Alternatives: Options like flavored seltzer water or fruit-infused water provide a better balance of flavor and pure hydration compared to diet soda.
Best Choice for Health: Pure, plain water remains the best option for meeting your body's hydration needs without unnecessary additives.

What is Diet Soda, Really?

While diet soda can contribute to your overall fluid intake, it is fundamentally different from plain water. The key lies in its ingredients, which include carbonated water, artificial sweeteners, and other additives.

The Composition of Diet Soda

Diet soda starts with carbonated water, but several other components are added to achieve its characteristic flavor and feel. These include:

Artificial or natural sweeteners: Compounds like aspartame, sucralose, or stevia provide sweetness with few to no calories. These can be 200 to 13,000 times sweeter than regular sugar.
Acids: Additives such as phosphoric and citric acid give diet soda its tartness. These acids are linked to dental enamel erosion over time.
Flavors and Colors: A variety of natural and artificial flavors and colors are used to create specific tastes and appearances.
Preservatives: Ingredients like potassium benzoate are added to extend the product's shelf life.
Caffeine: Many diet sodas contain caffeine, which acts as a mild diuretic.

The Difference Between Diet Soda and Water for Hydration

While diet soda contains a high percentage of water, the presence of other ingredients prevents it from being a direct substitute for pure, plain water.

A Better Look at Hydration

The purpose of hydration is to replenish the body with fluids needed for vital functions, a role that pure water performs perfectly. The additives in diet soda can complicate this process. For example, artificial sweeteners have been associated with increased cravings for unhealthy foods in some studies, potentially undermining overall health goals. Additionally, the acids present can negatively impact dental health by eroding enamel, a risk not associated with drinking plain water.

Diet Soda vs. Plain Water Comparison


Feature	Diet Soda	Plain Water
Primary Ingredient	Carbonated water (99%)	H2O (100%)
Calories	Zero	Zero
Sweeteners	Artificial or natural, with no calories	None
Acids	Contains phosphoric and citric acid	None
Flavor	Artificially flavored	Neutral
Dental Health	Potential for enamel erosion	Excellent for dental health
Nutritional Value	No significant nutritional benefits	Essential for all bodily functions
Diuretic Effect	Mild due to caffeine in some varieties	None

The Mild Diuretic Effect of Diet Soda

Some diet sodas contain caffeine, which is known to have a mild diuretic effect. This means it can cause an increase in urine production. While the effect is generally not significant enough to cause dehydration from moderate consumption, it does differ from plain water, which has no such effect. The National Academy of Sciences notes that the diuretic effects are transient and that caffeinated beverages still contribute to overall fluid needs.

A Better Approach to Healthy Hydration

For optimal health, plain water is the best choice for hydration. If you are trying to cut back on diet soda, there are healthier alternatives that still offer flavor without the artificial additives.

Flavored seltzer: Choose seltzer water with natural fruit flavors for a fizzy, refreshing drink without the artificial sweeteners or acids found in diet soda.
Infused water: Add slices of lemon, lime, cucumber, or berries to a pitcher of water for a simple, natural way to add flavor.
Unsweetened iced tea: Brewed tea, either black or herbal, provides flavor without artificial ingredients, and any diuretic effect from caffeine is minimal.

For more detailed information on diet soda's health effects, you can consult reliable sources like the Healthline article on Diet Soda.

Conclusion: The Bottom Line on Diet Soda and Water

So, is diet soda considered water? Technically, yes, in the sense that it contains a high percentage of water and contributes to your total fluid intake. However, it is not a healthy substitute for plain water. The presence of artificial sweeteners, acids, and other additives differentiates it significantly. For those seeking optimal hydration and overall wellness, prioritizing plain, pure water remains the best choice. For those who enjoy the flavor and carbonation, healthier options like flavored seltzer can provide a better alternative to relying on diet soda for your daily fluid needs.

Frequently Asked Questions

Yes, you can technically count diet soda towards your overall fluid intake because it is mostly water. However, it should not replace plain water as your primary source of hydration due to its added ingredients.

Diet soda is generally considered hydrating, as its high water content outweighs the mild diuretic effect of caffeine in some versions. It is not, however, as efficiently hydrating as plain water.

The primary difference lies in the additives. While both contain a high percentage of water, diet soda includes artificial sweeteners, acids, colors, and flavors that are not present in plain water.

The safety of artificial sweeteners has been widely studied, with many organizations concluding they are safe for consumption in moderation. However, some research suggests a potential link to increased sugar cravings and other health concerns.

Diet soda contains acids like citric and phosphoric acid, which can gradually erode tooth enamel over time. This makes your teeth more susceptible to cavities and decay.

For optimal hydration, plain water is best. If you desire flavor and carbonation, healthier alternatives include plain or naturally flavored seltzer, or water infused with fruit.

No, the mild diuretic effect of caffeine in diet soda does not completely negate its hydrating properties. According to the National Academy of Sciences, the diuretic effects are transient, and caffeinated beverages can still contribute to your overall fluid needs.