Does Costco's Kirkland Signature Water Contain Fluoride?

There has been much discussion about whether or not fluoride in water is beneficial and safe to consume. Ingesting this naturally-occurring mineral can be extremely helpful in preventing cavities and tooth decay, and many sources of drinking water have small amounts of added fluoride to promote these health benefits. However, the mineral can cause tooth discoloration and become toxic when consumed at high levels, especially for young children. No matter where you stand on the consumption of fluoride, it is important to be informed about what additives are present in the foods and beverages you consume.

When it comes to Costco's Kirkland Signature purified drinking water, there is no added fluoride present. Per the product's nutrition label, the additives in the purified drinking water include potassium bicarbonate, sodium bicarbonate, calcium citrate, sodium chloride, and magnesium oxide. These ingredients are mainly added to create a subtle mineral-like taste in the water. 

Importantly, Costco also sells Kirkland Signature natural spring water, which is a different product from its purified drinking water and does contain fluoride ions — about 0.3 ppm (parts per million). The two products look very similar, so those who are wary of fluoride should double-check that the water bottles at their Costco are labeled as "purified water."

Niagara Bottling, the company behind Costco's Kirkland brand water bottles, does not add any fluoride to its purified water products — however, there are multiple other additives present. These have long, scientific names that can feel rather intimidating if you aren't sure what purpose they serve. 

Most of the extra ingredients in Costco's water, including potassium bicarbonate and calcium citrate, are added to increase that "purified" taste — because let's be real, all water does have a taste. These additives create a distinctly mineral-like flavoring that can be described as clean, refreshing, and even subtly sweet. Sodium chloride, aka plain old salt, also assists in balancing the flavor of Kirkland's water.

In addition to the boost of flavor, magnesium oxide and sodium bicarbonate are added to increase water's pH level, lowering its acidity. This makes Costco's product similar to alkaline water, which some studies suggest can help to relieve acid reflux and promote hydration. That being said, there are big myths about alkaline water and what it can do for your body. What we know for sure is that all of the Kirkland water's additives are colorless, odorless, and perfectly safe to consume.