Hormesis: Once marginalized, evidence now supports hormesis as the most fundamental dose response

Abstract

The biomedical community made a fundamental error on the nature of the dose-response relationship early in the 20th century and has perpetuated this error to the present. The error was the byproduct of the conflict between homeopathy and traditional medicine. To deny support to homeopathy, leaders of the biomedical community rejected the hormetic biphasic dose-response model, the proposed explanatory principle of homeopathy. The threshold dose-response model was adopted as an alternative model, quickly becoming central to toxicology/pharmacology and their numerous applications. Despite its near-universal acceptance, no attempt was made to validate the ability of the threshold model to accurately predict responses in the below-threshold zone at the time of acceptance and throughout the 20th century. In contrast, the hormetic biphasic dose-response model became marginalized and was excluded from the mainstream of pharmacological/toxicological teaching and practice, textbook development, professional society journal publications, annual meeting presentations, grant funding, and use in government risk assessment. Over the last decade there has been a resurgence of interest in hormesis due to findings indicating that hormetic responses are common, reproducible, and generalizable, as well as independent of biological model, endpoint, and chemical class/physical stressor. Large-scale studies have indicated that the threshold model fails to accurately predict responses below the threshold, whereas the hormetic dose-response model performs very well. These findings indicate that the biomedical community made an error on the nature of the dose-response relationship, compromising the accuracy of toxicological and risk assessment practices, including environmental exposure standards, and impeding drug discovery/development and drug safety studies.