BHA and BHT

Chemistry of BHA and BHT Food Preservatives

Butylated hydroxyanisole (BHA) and the related compound butylated hydroxytoluene (BHT) are phenolic compounds that are often added to foods to preserve fats.

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 oxidative characteristics and/or metabolites of BHA and BHT may contribute to carcinogenicity or tumorigenicity; however the same reactions may combat oxidative stress. There is evidence that certain persons may have difficulty metabolizing BHA and BHT, resulting in health and behavior changes. 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.

• Adverse Effects of Some 'Inactive' Ingredients - Summary of health effects reported for dyes and preservatives, including food colors, BHA, BHT, sodium benzoate, nitrates, nitrites, and monosodium glutamate.

• Bioassay of Butylated Hydroxytoluene for Carcinogenicity - Abstract for NTIS# PB29-8539/AS, which includes a summary of the results of the study, diagrams of BHT, and an explanation of methods and analysis.

• Chemical Cuisine: CSPI's Guide to Food Additives - This site includes a glossary, explanation of cancer testing, alphabetical listing of additives, and a list of additives that have been banned.

• Common Food Additives - CNN In-Depth provides this chart listing additives and their chemistry, uses, common products containing the additives, and reported side effects.

• Do Food Additives Subtract from Health? - This is a Businessweek article about the effects of additive on health.

• Drugs Additives Causing Side Effects - Note that defining a substance in a drug as 'inert' or 'inactive' just means the substance and presumably its metabolites don't compromise a drug's effectiveness. The substance need not be 'inert' in biochemical reactions.

• FDA Almanac Fiscal Year 1997 - The Center for Food Safety and Applied Nutrition provides an overview of its responsibilities.

• Food Additives - This 1992 Food and Drug Administration brochure answers frequently asked questions about food additives.

• Food Additives - Are They Safe? - The Cooperative Extension of the College of Agriculture & Life Sciences at the University of Arizona offers this article, which emphasizes the reasons additives are used and a list of steps that can be taken to minimize accidental exposure to contaminants.

• Food Allergies - Rare but Risky - The US FDA distinguishes betweem food allergies and intolerances and identifies several additives (specifically aspartame, monosodium glutamate, sulfites, and FD&C Yellow No. 5 or tartrazine) known to cause reactions in susceptible persons.

• Food and Asthma - John Neil Rhoades's article includes a list of several foods and additives associated with asthma and chemical sensitivity.

• Fresh Look at Food Preservatives - Judith E. Foulke provides an overview of 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.

• Some Studies on BHT and BHA - The Feingold Association maintains this collection of links to references. Excerpts from selected articles are included.

• Summary of Color Additives Listed for Use in the United States in Foods, Drugs, Cosmetics, and Medical Devices - This is the US FDA comprehensive list of additives, year approved, and uses and restrictions.

• 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.

• The Reaction of Butylated Hydroxyanisole and Its Metabolites with Some Arylamines: Investigations of Product Mutagenicity - Abstract for the Kalus, Münzner, and W.G. Filby paper.