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Estimating the range of the maximum hormetic stimulatory response

Calabrese, Edward J., Agathokleous, Evgenios, Kozumbo, Walter J., Stanek, Edward J., Leonard, Denise
Environmental research 2019 v.170 pp. 337-343
databases, environmental health, humans, microorganisms
An ever-expanding hormetic database (HDB) was used to demonstrate that the median maximal hormetic stimulatory response (MHSR) of biphasic dose-response relationships increases in value with an increase in the number of stimulatory doses/concentrations that are administered below the estimated threshold/ZEP (zero equivalent point – i.e., the dose where the response crosses the control group value). With only one dose or concentration administered below the ZEP, the median MHSR for microbes (in vitro), animals (in vitro and in vivo), and plants (in vitro and in vivo) ranged between 120% and 125% of the control response. However, when individual agents having at least six doses below the ZEP were mined from the HDB (and a median MHSR then determined), the median MHSR increased to 160–190%. This progressive increase in the MHSR appears to be due to several factors, including (i) the enhanced capacity of additional doses in the stimulatory hormetic zone to better estimate the response optima, and (ii) enhanced variability due to the presence of more doses in the stimulatory zone. This study offers a novel perspective for improving research protocols, unraveling the limits of biological plasticity, understanding low-level stress biology, advancing human and ecological health, and enhancing human performance.