What is benzoic acid?
Benzoic acid is a chemical that occurs naturally in many foods, and may also be added synthetically to foods, where it functions as a preservative (antibacterial and antifungal) (1, 2).
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 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 can 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 as an add-on treatment for schizophrenia has been shown to decrease symptoms by 21%, without any significant side effects, likely due to its ability to block DAAO enzymes, which are overactive in schizophrenia (32).