Chemistry of BHA and BHT Food Preservatives

BHA and BHT are used to preserve fats and oils.
BHA and BHT are used to preserve fats and oils. Maximilian Stock Ltd. / Getty Images

Butylated hydroxyanisole (BHA) and the related compound butylated hydroxytoluene (BHT) are phenolic compounds that are often added to foods to preserve fats and oils and keep them from becoming rancid. They are added to food, cosmetics, and packing of products that contain fats to maintain nutrient levels, color, flavor, and odor. BHT is also sold as a dietary supplement for use as an antioxidant.

The chemicals are found in an extensive list of products, yet there is concern about their safety. Take a look at the chemical properties of these molecules, how they work, and why their use is controversial.

BHA Characteristics:

  • BHA is a mixture of the isomers 3-tert-butyl-4-hydroxyanisole and 2-tert-butyl-4-hydroxyanisole. Also known as BOA, tert-butyl-4-hydroxyanisole, (1,1-dimethylethyl)-4-methoxyphenol, tert-butyl-4-methoxyphenol, antioxyne B, and under various trade names
  • Molecular formula C11H16O2
  • White or yellowish waxy solid
  • Faint characteristic aromatic odor

BHT Characteristics:

  • Also known as 3,5-di-tert-butyl-4-hydroxytoluene; methyl-di-tert-butylphenol; 2,6-di-tert-butyl-para-cresol
  • Molecular formula C15H24O
  • White powder

How Do They Preserve Food?

BHA and BHT are antioxidants. Oxygen reacts preferentially with BHA or BHT rather than oxidizing fats or oils, thereby protecting them from spoilage.

In addition to being oxidizable, BHA and BHT are fat-soluble. Both molecules are incompatible with ferric salts. In addition to preserving foods, BHA and BHT are also used to preserve fats and oils in cosmetics and pharmaceuticals.

What Foods Contain BHA and BHT?

BHA is generally used to keep fats from becoming rancid.

It is also used as a yeast de-foaming agent. BHA is found in butter, meats, cereals, chewing gum, baked goods, snack foods, dehydrated potatoes, and beer. It is also found in animal feed, food packaging, cosmetics, rubber products, and petroleum products.

BHT also prevents oxidative rancidity of fats. It is used to preserve food odor, color, and flavor. Many packaging materials incorporate BHT. It is also added directly to shortening, cereals, and other foods containing fats and oils.

Are BHA and BHT Safe?

Both BHA and BHT have undergone the additive application and review process required by the US Food and Drug Administration. However, the same chemical properties which make BHA and BHT excellent preservatives may also be implicated in health effects. The research leads to conflicting conclusions. The oxidative characteristics and/or metabolites of BHA and BHT may contribute to carcinogenicity or tumorigenicity; however, the same reactions may combat oxidative stress and help detoxify carcinogens. Some studies indicate low doses of BHA are toxic to cells, while higher doses may be protective, while other studies yield exactly the opposite results.

There is evidence that certain persons may have difficulty metabolizing BHA and BHT, resulting in health and behavior changes.

Yet, BHA and BHT may have antiviral and antimicrobial activities. Research is underway concerning the use of BHT in the treatment of herpes simplex and AIDS.

References and Additional Reading

This is a fairly long list of online references. While the chemistry and effectiveness of BHA, BHT, and other additives within food is straightforward, the controversy surrounding health effects is hot, so several points of view are available.

  • Common Food Additives - CNN In-Depth provides this chart listing additives and their chemistry, uses, common products containing the additives, and reported side effects.
  • Fresh Look at Food Preservatives - Judith E. Foulke provides an overview of the preservative use and regulation, she specifically discusses BHA, BHT, and sulfites.
  • Multiple Chemical Sensitivity Homepage - This site discusses the inability of damaged nervous tissue to metabolize specific toxins.
  • The Feingold Association of the United States - The Feingold Association provides extensive information about the effects of petroleum-derived additives and salicylates (both natural and synthetic) on the behavior/health of susceptible persons.