Review: putative mutagens and carcinogens in foods. III. Butylated hydroxytoluene (BHT)

Although the average American's daily consumption of BHT can be measured in milligrams, there are numerous reports that BHT causes organ damage in laboratory animals. Only a few genotoxic effects of BHT have been reported, however, including mutagenicity in the abnormal sperm assay and ambiguous results regarding its teratogenicity. More dramatic are the modulatory effects of BHT on the actions of established mutagens and carcinogens. BHT can either enhance or inhibit mutagenic potency, depending on the substance tested. For example, in the Ames test, BHT is antimutagenic towards benzo(a)pyrene, but increases the number of Salmonella revertants induced by aflatoxin B1. BHT is one of the few compounds to have both tumor prophylactic and tumor promoting capacities. It is the temporal sequence in which BHT and carcinogens are administered to test animals which determines how BHT affects the response to these carcinogens. In common with other antioxidants, BHT inhibits the ability of carcinogens to induce tumors in various rodent organs when the animal is given BHT prior to carcinogen treatment. Unlike other antioxidants, however, the number of tumors increase when BHT is administered after carcinogen exposure. The comutagenic and cocarcinogenic properties of BHT have been demonstrated in tests ranging from the Ames test to cell transformation procedures to in vivo assays. These effects are probably mediated by metabolites of BHT, rather than by BHT itself.