I have just started cleaning my cats teeth and after reading your post I checked the ingredients, and yes Sodium Benzoate is there and I'm going to change. I took this quote from Wikipedia so I don't know how accurate it is:-
Sodium benzoate is a preservative. It is bacteriostatic and fungistatic under acidic conditions. It is used most prevalently in acidic foods such as salad dressings (vinegar), carbonated drinks (carbonic acid), jams and fruit juices (citric acid), pickles (vinegar), and condiments. It is also found in alcohol-based mouthwash and silver polish.[citation needed] It can also be found in cough syrups like Robitussin.[1] Sodium benzoate is declared on a product label as 'sodium benzoate' or E211.
It is also used in fireworks as a fuel in whistle mix, a powder which emits a whistling noise when compressed into a tube and ignited.[citation needed]
Sodium benzoate is produced by the neutralization of benzoic acid with sodium hydroxide.[2] Benzoic acid is detectable at low levels in cranberries, prunes, greengage plums, cinnamon, ripe cloves, and apples.[citation needed] Though benzoic acid is a more effective preservative, sodium benzoate is more commonly used as a food additive because benzoic acid does not dissolve well in water.[2] Concentration as a preservative is limited by the FDA in the U.S. to 0.1% by weight. The International Programme on Chemical Safety found no adverse effects in humans at doses of 647–825 mg/kg of body weight per day.[3][4]
Cats have a significantly lower tolerance against benzoic acid and its salts than rats and mice.[5] Sodium benzoate is, however, allowed as an animal food additive at up to 0.1%, according to AFCO's official publication.
In combination with ascorbic acid (vitamin C, E300), sodium benzoate and potassium benzoate may form benzene,[8] a known carcinogen. Heat, light and shelf life can affect the rate at which benzene is formed.
Professor Piper of the University of Sheffield claims that sodium benzoate by itself can damage and inactivate vital parts of DNA in a cell's mitochondria. Mitochondria consume oxygen to generate ATP, the body's energy currency. If they are damaged due to disease, the cell malfunctions and may enter apoptosis. There are many illnesses now tied to DNA damage, including Parkinson's and other neurodegenerative diseases, but above all, the aging process in general.
No more for my cat.