Benzoate is a preservative, a medicine, and a naturally occurring compound found in everyday fruits and spices. In its most common form, sodium benzoate, it keeps bacteria and mold from growing in foods, drinks, cosmetics, and personal care products. But it also has a surprising second life as a hospital treatment for a rare genetic condition, and it shows up naturally in foods like blueberries and cinnamon.
Food Preservation
The most widespread use of benzoate is keeping food fresh. Sodium benzoate and potassium benzoate prevent the growth of bacteria, yeast, and mold, which is why they appear in so many shelf-stable products. You’ll find them in carbonated soft drinks, fruit juices, jams and jellies, pickles, salad dressings, condiments, sauces, mayonnaise, margarine, tomato paste, wines, and packaged snack foods. Major brands rely on them: Coca-Cola uses sodium benzoate, potassium benzoate, and potassium sorbate as preservatives, while Fanta, Sprite, and Pepsi products also list benzoate on their labels.
Benzoate works best in acidic environments. Its germ-killing power increases dramatically as pH drops. At a neutral pH of 7.0, you’d need an extremely high concentration (over 10,000 parts per million) to kill common foodborne bacteria like E. coli, Salmonella, and Listeria. Drop the pH to 4.0, and just 1,000 ppm does the job. That’s why benzoate is paired with naturally acidic foods like fruit juices, sodas, and vinegar-based condiments rather than added to something like plain bread or milk.
Cosmetics and Personal Care Products
Potassium benzoate serves the same preservative role in beauty and skincare products. Shampoos, conditioners, facial cleansers, and moisturizers often contain it to extend shelf life and prevent mold from developing in products that sit in warm, humid bathrooms for months. Without a preservative like benzoate, water-based cosmetics would become breeding grounds for bacteria and fungi relatively quickly.
Treating a Rare Genetic Condition
Sodium benzoate has an entirely separate use in medicine. It’s an FDA-approved treatment for urea cycle disorders, a group of rare genetic conditions where the body can’t properly process nitrogen from protein. Normally, your liver converts nitrogen waste into urea, which your kidneys then flush out. In people with urea cycle disorders, this process is broken, and toxic ammonia builds up in the blood.
Sodium benzoate offers the body a workaround. It binds to an amino acid called glycine in the liver to form a compound called hippuric acid, which the kidneys can rapidly filter out. Each molecule of benzoate carries away one molecule of nitrogen waste this way, essentially creating an alternative exit route for nitrogen that can’t leave through the normal urea pathway. In hospitals, it’s given intravenously alongside another compound during acute episodes of dangerously high ammonia levels.
Where Benzoate Occurs Naturally
Benzoate isn’t purely a lab-made additive. Benzoic acid, the parent compound of all benzoates, occurs naturally in a range of fruits, herbs, and spices. Blueberries are the richest natural source, containing up to 1,300 mg per kilogram. Cinnamon contains around 335 mg/kg, and even cottage cheese has about 90 mg/kg. Cranberries, bilberries, strawberries, cloves, thyme, nutmeg, and star anise all contain measurable amounts. So even if you avoid processed foods entirely, you’re likely consuming some benzoate through your diet.
Safety Limits
The World Health Organization sets the acceptable daily intake for benzoic acid and its salts at 0 to 20 mg per kilogram of body weight. For a 70 kg (154 lb) adult, that works out to 1,400 mg per day. This limit was updated in 2021, quadrupling the previous threshold of 5 mg/kg after a reassessment of how the human body processes benzoate compared to the animals used in safety studies. At normal dietary levels, benzoate is metabolized quickly and excreted in urine.
The Benzene Concern
One well-documented safety issue involves what happens when benzoate meets vitamin C. In beverages that contain both benzoate salts and ascorbic acid (vitamin C), a small amount of benzene, a known carcinogen, can form. The levels are very low, measured in parts per billion, but heat and light exposure accelerate the reaction. This is why some soft drink manufacturers have reformulated products over the years to avoid combining benzoate with vitamin C in the same bottle. If you store benzoate-containing drinks in a cool, dark place, benzene formation is minimized.