Sodium benzoate is a preservative added to some sodas, packaged foods, and personal care products to prolong shelf life.

Some people claim that this man-made additive is harmless, while others link it to cancer and other health problems.

What Is Sodium Benzoate?

Sodium benzoate is best known as a preservative used in processed foods and beverages to extend shelf life, though it has several other uses.

It’s an odorless, crystalline powder made by combining benzoic acid and sodium hydroxide. Benzoic acid is a good preservative on its own, and combining it with sodium hydroxide helps it dissolve in products (1).

Sodium benzoate does not occur naturally, but benzoic acid is found in many plants, including cinnamon, cloves, tomatoes, berries, plums, apples, and cranberries (2Trusted Source).

Additionally, certain bacteria produce benzoic acid when fermenting dairy products like yogurt (1, 3Trusted Source).

Various Uses in Different Industries

Aside from its use in processed foods and beverages, sodium benzoate is also added to some medicines, cosmetics, personal care products, and industrial products.

Here’s a closer look at its many functions.

Foods and Beverages

Sodium benzoate is the first preservative the FDA allowed in foods and still a widely used food additive. It’s classified as Generally Recognized As Safe (GRAS), meaning that experts consider it safe when used as intended (1, 4).

It’s approved internationally as a food additive and is assigned the identifying number 211. For example, it’s listed as E211 in European food products (5).

Sodium benzoate inhibits the growth of potentially harmful bacteria, mold, and other microbes in food, thus deterring spoilage. It’s particularly effective in acidic foods (6Trusted Source).

Therefore, it’s commonly used in foods, such as soda, bottled lemon juice, pickles, jelly, salad dressing, soy sauce, and other condiments.

Medications

Sodium benzoate is used as a preservative in some over-the-counter and prescription medications, particularly in liquid medicines like cough syrup.

Additionally, it can be a lubricant in pill manufacturing and makes tablets transparent and smooth, helping them break down rapidly after you swallow them (1).

Lastly, larger amounts of sodium benzoate may be prescribed to treat elevated blood levels of ammonia. Ammonia is a byproduct of protein breakdown, and blood levels may become dangerously high in certain medical conditions (2Trusted Source).

Other Uses

Sodium benzoate is commonly used as a preservative in cosmetics and personal care items, such as hair products, baby wipes, toothpaste, and mouthwash (2Trusted Source).

It also has industrial uses. One of its biggest applications is to deter corrosion, such as in coolants for car engines (2Trusted Source, 7).

What’s more, it may be used as a stabilizer in photo processing and to improve the strength of some types of plastic (2Trusted Source).

Possible Health Problems

Some people are generally leery of all chemical additives, including sodium benzoate. Preliminary studies raise questions about its safety, but more research is needed.

Converts to a Potential Cancer Agent

A large concern over the use of sodium benzoate is its ability to convert to benzene, a known carcinogen.

Benzene can form in soda and other drinks that contain both sodium benzoate and vitamin C (ascorbic acid) (8Trusted Source).

Notably, diet beverages are more prone to benzene formation, as the sugar in regular sodas and fruit drinks may reduce its formation (9Trusted Source).

Other factors, including exposure to heat and light, as well as longer storage periods, can increase benzene levels (9Trusted Source).

In 2005, 10 out of 200 sodas and other fruit drinks tested by the FDA contained more than 5 parts per billion (ppb) of benzene — which is the limit for safe drinking water set by the US Environmental Protection Agency (EPA) (8Trusted Source).

Particularly, fruit-flavored diet sodas and juice drinks exceeded 5 ppb of benzene. Since then, these ten drinks have either been reformulated to yield acceptable levels or have had sodium benzoate removed entirely.

The FDA has not published more recent product analyses but has stated that the low levels of benzene found in beverages don’t pose a health risk (8Trusted Source).

Still, long-term studies assessing the relationship between regularly consuming low levels of benzene and cancer risk are lacking (9Trusted Source).