Scientific procedures and possible alternative assays in GRAS determination

A food substance can be designated as Generally Recognized as Safe (GRAS) based on the outcomes of scientific procedures or experience of common use in food.  Data used for GRAS determination is provided by the Sponsor and is derived from human, animal, analytical, and other studies, usually published, although they can be supported by unpublished corroborative evidence, appropriate to establish the safety of a substance under the conditions of intended use (Federal Register 1977).  Such evidence includes data on the identity and specifications of the substance, its properties of absorption, distribution, metabolism and excretion, and depending on the level of concern for safety, data on genotoxicity, acute and subchronic toxicity, reproductive and developmental toxicity and carcinogenicity (Tab. 1).

To decide which toxicity assays are needed for safety assessment, the Food and Drug Administration (FDA) assigns compounds to Concern Levels: Concern Level I, or low, requires only genotoxicity and acute toxicity testing; Concern Level II, or intermediate, additionally needs data from subchronic, reproductive and developmental toxicity studies; for Concern Level III, or high, one year non rodent and rodent carcinogenicity studies are necessary (Tab. 1). This classification is determined by several considerations, including structure category assignment and potential cumulative human exposure. Based on the chemical structure a compound can be assigned one of the following categories: A, low toxic potential; B, adverse effects other than mutagenicity and carcinogenicity; C, structurally related to reported mutagens or carcinogens. At this level, computational toxicology could be also involved.

Clinical technical evidence of safety involves human studies.  Also data in the Center for Food Safety and Applied Nutrition (CFSAN) Adverse Event Reporting System (CAERS), which requires reporting of serious adverse events for dietary supplements, is relevant.

Based on the outcomes of available studies, an independent Expert Panel of at least 3 qualified experts from different backgrounds, must unanimously conclude that other qualified scientists would agree with the conclusion (i.e., there would be a “consensus” that the substance is GRAS). This conclusion is specific to the intended conditions of the use of the candidate food ingredient.

The use of alternative procedures can significantly improve the GRAS process (Williams et al., 2014a; 2014b).  Among such alternatives are in Ovo Genotoxicity Assays, i.e. Chicken Egg Genotoxicity Assay (CEGA) and Turkey Egg Genotoxicity Assay (TEGA), that have been developed as an enhanced tool for the assessment of the potential of a chemical to induce DNA damage (Kobets et al., 2016; Williams et al., 2014 a). The model, which is intermediate between in vitro and in vivo assays, uses fertilized avian eggs injected with the test compound for 3 days. The endpoints of the assays include detection of DNA adducts and DNA strand breaks, evaluation of the histopathological changes, and for the chicken, analysis of gene expression profile. The model has multiple advantages, and potentially can substitute for in vivo testing.

Tab. 1. Scientific procedures involved in GRAS determination.

The Accelerated Carcinogenicity Bioassay (ACB), designed as an alternative to the carcinogenicity testing (Iatropoulos et al., 2001; Williams et al., 2014b), is conducted in either rats and/or mice and involves ancillary endpoints (e.g. cell proliferation, preneoplastic lesions). The endpoints are assessed in six or more critical target tissues, after administration of test substance for 16 weeks as possible cancer initiator followed for 24 weeks either by controlled diet or a known tumor promoter; or the administration of the test substance for 24 weeks as a possible promoter after administration of known initiating carcinogen for 16 weeks.

Tetyana Kobets, Gary M. Williams
Department of Pathology, New York Medical College, Valhalla, NY, USA

 

Publication

GRAS determination scientific procedures and possible alternatives.
Williams GM, Kobets T, Iatropoulos MJ, Duan JD, Brunnemann KD
Regul Toxicol Pharmacol. 2016 Aug

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