The guiding principle related to animal data is as follows: “Even in the absence of information on adverse events in humans, evidence of harm from animal studies is often indicative of potential harm to humans. This indication assumes greatest importance when the route of exposure is oral, the formulation tested is identical or highly similar to that consumed by humans in an ingredient, and more than one species shows the same or similar toxicity.”

The rationale and importance of this principle have been presented, and the following corollaries, along with their rationales and limitations:

• In the absence of specific evidence that certain animal study findings are irrelevant to humans, animal evidence should be used to evaluate potential human risk.

• A lack of observed or reported detrimental effects in an animal study is not evidence that a particular substance is “safe.”

• Veterinary toxicology information may be useful when it corroborates concerns raised by other types of data. Independent of other types of data, evidence of harm in livestock and other veterinary toxicology information is appropriate to consider as a signal prompting an initial review of an ingredient. In addition, the veterinary toxicology literature is also useful for generating hypotheses in need of testing in well-established animal models.

• When there is no detailed understanding of pharmacokinetics to make a comparison between animals or humans possible, it is appropriate to assume that the most sensitive experimental animal studies are relevant to human health.

• Much of the animal study data available for dietary supplement ingredients will not have the characteristics of ideal studies, but these studies should nonetheless be considered if they suggest possible human health risk.

• Animal studies that predict possible serious harm or death warrant more attention than those that predict mild, self-limiting effects in humans.

• Certain chronic animal toxicity or adverse biological effects data should be considered as immediate cause for higher or moderate concern, regardless of the presence of high-quality human data suggesting no acute toxicity (see Category A in Table 5-1).

• The default assumption for cancer is a linear low-dose extrapolation. Carcinogenicity findings, particularly those that are accompanied by evidence of genotoxicity and observed in animals at ingested amounts within 100× of expected human exposure, are of particular concern.