What is benzoic acid?
It is most commonly used in acidic foods since it has stronger antibacterial and antifungal abilities at a lower pH.
It is rapidly metabolized by the body & excreted in the urine as hippuric acid within 24 hours of consumption. Peak blood concentrations are reached 1 to 2 hours after a meal (3).
Names to look for on labels:
- Benzoic acid
- Benzoate derivatives (any chemical with the word “benzoate” in it)
- Calcium benzoate
- Potassium benzoate
- Sodium benzoate
Natural food sources of benzoates:
- Anise (33)
- Bilberries (up to 1300 mg/kg) (3)
- Blueberries (up to 1300 mg/kg) (3)
- Cheeses, with a higher concentration near the rind (up to 250 mg/kg, but typically closer to 20 mg/kg) (4, 5, 6, 7)
- Cherry bark (used in cherry flavoring) (34)
- Cinnamon (336 mg/kg) (8)
- Cloves (15-50mg/kg) (8)
- Cowberry (up to 1300 mg/kg) (3)
- Cottage cheese (90 mg/kg) (9)
- Cranberries (up to 1300 mg/kg) (10)
- Fermented milk products (up to 36 mg/L) (11, 12)
- Huckleberry (up to 1300 mg/kg) (3)
- Lingonberries(up to 1300 mg/kg) (13)
- Milk (raw or ultra-high temp pasteurized) (up to 28 mg/L) (14, 15)
- Nutmeg (15-50mg/kg) (8)
- Salvia (15-50mg/kg) (8)
- Star anise (33)
- Strawberries (up to 29 mg/kg) (8)
- Thyme (15-50mg/kg) (8)
- Whortleberry (up to 1300 mg/kg) (3)
- Wood mushrooms (but not button mushrooms) (16)
- Yogurt – bacterial fermentation can create benzoic acid (up to 56 mg/kg) (17)
Some lists also include other foods, like almonds, apples, apricots, cherries, cocoa, snap peas, but technically they contain related compounds like benzyl alcohol and benzaldehyde, which are not quite the same thing.
When plants get infected with pathogens, benzoic acid concentrations can increase to protect them. Levels of almost 250mg/kg have been detected in apples after the plant was infected w. fungus (18).
Other natural sources:
- The resin of Styrax trees contains up to 20% benzoic acid (19).
- The fluid that beavers spray from their castor sacs to mark their territories is rich in benzoic acid (20).
Foods that often contain added benzoates:
- Blue cheese
- Bottled Asian sauces
- Bottled lemon & lime juice
- Flavored yogurt
- Fruit juice
- Hot chocolate
- Some shellfish
Legally, the FDA limits benzoic acid concentrations of no more than 0.1% when used in food (3).
The FAO generally limits benzoate concentrations to no more than 1000 mg/kg, but some foods have higher limits (3):
- Cooked shrimp, up to 6,000 mg/kg
- Liquid egg products, up to 5,000 mg/kg
- Vegetable pulps, up to 3,000 mg/kg
- Cooked seafood & seafood products, up to 2,000 mg/kg
- Brined vegetables, up to 2,000 mg/kg
- Soy sauce, up to 2,000 mg/kg
- Salads & sandwich spread, up to 1,500 mg/kg
- Dietetic medical foods, up to 1,500 mg/kg
Personal care products that often contain benzoates:
- Acne cream
- Eye cream
Some benzoates can be absorbed through the skin, but not as much as when they are eaten (estimates range from 22-89%) (3).
Adverse reactions to benzoates:
- There have been separate reports in the literature of itchy skin, hives, and chronic rhinitis caused by benzoates in food or products (21, 22, 23).
- Benzoates in food (in combination with artificial food dyes) has been associated with worsening hyperactivity in some 3-year-old children (24).
- Asthma may be worsened by the benzoates in some antiasthmatic drugs (25).
- Contact allergies, acute leukoclastic vasculitis, and even anaphylaxis to benzoates have also been reported (26, 27, 28).
- Benzoic acid, potassium benzoate, and sodium benzoate can increase chromosomal aberrations in white blood cells when incubated together for at least 24 hours (but in vivo studies are needed) (29, 30).
There is no defined “safe” level of benzoic acid or sodium benzoate. It is GRAS (generally recognized as safe) for food, medications, cosmetics, and personal care products by FAO/WHO and the FDA/USDA.
The FAO does recommend limiting intake to no more than 5 mg/kg body weight per day (3).
Of note, benzoic acid is very toxic to cats (they lack the ability to detoxify it in their livers) and can be lethal at doses of 0.5 g/kg of body weight (31).
Therapeutic uses for benzoates:
Taking 1 gram of sodium benzoate per day for 6 weeks has been shown to decrease symptoms of schizophrenia by 21%, without any significant side effects, due to its ability to block DAAO enzymes, which are overactive in schizophrenia (32).
Concerns over carcinogenic benzene in soda:
Soda can contain higher than allowed levels of benzene, a known carcinogen.
Benzene can form when the preservative sodium benzoate interacts with ascorbic acid (vitamin C).
This happens when the ascorbic acid reacts with metal ions in the water to create hydroxyl (-OH) free radicals. At the same time, sodium benzoate breaks down to benzoic acid when in acidic conditions. When the hydroxyl radicals combine with the benzoic acid, it removes one CO2 molecule from the benzoic acid, creating benzene.
The FDA was first notified of this issue in 1990. After some independent testing, these claims were confirmed.
Soft drink companies agreed to reformulate their beverages, and no legal action was taken, and no public notification was given.
In 1993, a journal article was published in The Journal of Agricultural and Food Chemistry, to help spread the information to the public and other companies.
The solution is for soda companies to stop using ascorbic acid in their sodas, and/or discontinue the use of sodium benzoate in sodas that contain naturally acidic juices.
Sodium benzoate is added because it inhibits bacterial & fungal growth. Ascorbic acid is added as an antioxidant to extend shelf life.
Currently, most sodas do not use sodium benzoate anymore, due to this information, but a few do, so it is important to read labels!
Coca-Cola brand beverages that still contain benzoates:
- Barq’s Rootbeer
- Barq’s Diet Rootbeer
- Diet Coke
- Coke Zero
- Coca Cola Life
- Coca Cola Zero Sugar
- Coca Cola Cherry Zero
- Fruit Water
- Fuze Iced Tea
- Mello Yello
- Mello Yello Zero
- Minute Maid Sparkling
- Minute Maid Canned Beverages
- Mr. Pibb
- Pibb Zero & Xtra
- Seagram’s Ginger Ale
- Seagram’s Tonic Water
- Sprite Zero
- Yum-e Tummies