Academic journal article Environmental Health Perspectives

The Importance of Hormesis to Public Health

Academic journal article Environmental Health Perspectives

The Importance of Hormesis to Public Health

Article excerpt

BACKGROUND: Hormesis is a specific type of nonmonotonic dose response whose occurrence has been documented across a broad range of biological models, diverse types of exposure, and a variety of outcomes. The effects that occur at various points along this curve can be interpreted as beneficial or detrimental, depending on the biological or ecologic context in which they occur.

OBJECTIVE: Because hormesis appears to be a relatively common phenomenon that has not yet been incorporated into regulatory practice, the objective of this commentary is to explore some of its more obvious public health and risk assessment implications, with particular reference to issues raised recently within this journal by other authors.

DISCUSSION: Hormesis appears to be more common than dose-response curves that are currently used in the risk assessment process [e.g., linear no-threshold (LNT)]. Although a number of mechanisms have been identified that explain many hormetic dose-response relationships, better understanding of this phenomenon will likely lead to different strategies not only for the prevention and treatment of disease but also for the promotion of improved public health as it relates to both specific and more holistic health outcomes.

CONCLUSIONS: We believe that ignoring hormesis is poor policy because it ignores knowledge that could be used to improve public health.

KEY WORDS: biphasic, dose response, hormesis, J-shaped, risk assessment, U-shaped. Environ Health Perspect 114:1631-1635 (2006). doi:10.1289/ehp.8606 available via http://dx.doi.org/ [Online 10 July 2006]

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The acceptance of the concept of hormesis, a specific type of nonmonotonic dose response, has accelerated in recent years (Academie Nationale de Medecine 2005; Cendergreen et al. 2005; Kaiser 2003; Puatanachokchai et al. 2005; Randic and Estrada 2005; Renner 2003). Nonetheless, it has not been without its detractors. One article critical of the concept was published last year in Environmental Health Perspectives (Thayer et al. 2005). It provided a summary of the major points of contention and thus a convenient vehicle for us to use in responding to opposing perspectives.

Although Thayer et al. (2005) tacitly acknowledged the existence of the phenomenon, they argued that no consideration should be given to hormesis in assessments of chemical risks for regulatory purposes. We disagree with their conclusion, but believe some of their points have merit--with important clarifications. We also believe that the proper understanding and utilization of hormesis will do a much better job of both protecting and promoting public health than the policy-based defaults that are currently in use.

Contrary to the assertion of Thayer et al. (2005) that hormesis is rare, it is a ubiquitous natural phenomenon (Calabrese and Blain 2005). Although given many names, hormesis has been observed in the fields of medicine (Brandes 2005; Celik et al. 2005), molecular biology (Randic and Estrada 2005), pharmacology (Chiueh et al. 2005), nutrition (Lindsay 2005), aging and geriatrics (Lamming et al. 2004; Rattan 2004a, 2004b, 2004c, 2005; Sinclair et al. 2005), agriculture (Brandt et al. 2004; Shama and Alderson 2005), microbiology (Brugmann and Firmani 2005), immunology (Dietert 2005; Liu 2003), toxicology (Stebbing 2000), exercise physiology (Radak et al. 2005), and carcinogenesis (Fukushima et al. 2005)--literally, across the biological spectrum. It has also been observed in relation to disparate outcomes from the isolated single cellular process to the more holistic (e.g., growth, longevity, disease, death) that likely result from a complex interplay of multiple factors and mechanisms (Calabrese 2005d).

In some fields, such as pharmacology and nutrition, these findings have been used directly or indirectly to improve human health. In others, they have been dismissed as artifacts and ignored (Calabrese 2005b). …

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