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Xenohormesis - What Doesn't Kill Plants Makes Us Stronger

Dean Pomerleau

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I posted about this a while back on the (now defunct) CR email list, but I thought it interesting enough to bring up here, especially since the forum enables the inclusion of a very nice graphic illustration (see below)...


CR (and exercise) are thought to serve as stressors which actively upregulate endogenous repair and defensive mechanisms that improve health and longevity in insects and animals. But plants have also had billions of years to evolve similar endogenous mechanisms to protect themselves from environmental stresses like drought, famine, insects, diseases, etc. The idea of xenohormesis is that phytochemicals are the signalling mechanisms of these stress responses in plants, and they are healthy for us because we share many of the same biochemical pathways with plants.


The way Dr. Greger puts it in this video, rather than endure the hardship (sic?!) of calorie restriction ourselves to upregulate our defenses, why not torture plants, then eat them to gain the benefits of CR via the CR memetics they produce in response to the stress.


What I thought was most interesting in the video was this figure (click to enlarge):




which shows how specific, well-known plant phytonutrients (Curcumin in turmeric/curry powder, Resveratrol in red wine and ECGC in green tea), influence the same pathways that are modulated by calorie restriction (i.e. "low energy" in the diagram), and therefore may serve as (partial) CR mimetics.


For more discussion on the topic, see this thread from the old mailing list.



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On this same topic of hormesis, AL Pater just posted this recent Mattson paper [1] that reviews the health benefits of periodically stressing the body via intermittent fasting, exercise and "toxins" from plants. I particularly liked this sentence from the abstract :


"As a consequence of the modern 'couch potato' lifestyle, signaling pathways that mediate beneficial effects of environmental challenges on health and disease resistance are disengaged, thereby rendering people vulnerable to obesity, diabetes, cardiovascular disease, cancers and neurodegenerative disorders."


It seems the adage "no pain, no gain" has some real validity to it when it comes to health.




Challenging oneself intermittently to improve health.

Mattson MP.

Dose Response. 2014 Oct 20;12(4):600-18. doi: 10.2203/dose-response.14-028.Mattson. eCollection 2014 Dec.


Free PMC Article






Humans and their predecessors evolved in environments where they were challenged intermittently with: 1) food scarcity; 2) the need for aerobic fitness to catch/kill prey and avoid or repel attackers; and 3) exposure to biological toxins present in foodstuffs. Accordingly, cells and organ systems acquired and retained molecular signaling and metabolic pathways through which the environmental challenges enhanced the functionality and resilience of the cells and organisms. Within the past 60 years there has been a precipitous diminution of such challenges in modern societies because of the development of technologies that provide a continuous supply of energy-dense processed foods and that largely eliminate the need for physical exertion. As a consequence of the modern 'couch potato' lifestyle, signaling pathways that mediate beneficial effects of environmental challenges on health and disease resistance are disengaged, thereby rendering people vulnerable to obesity, diabetes, cardiovascular disease, cancers and neurodegenerative disorders. Reversal of the epidemic of diseases caused by unchallenging lifestyles will require a society-wide effort to re-introduce intermittent fasting, exercise and consumption of plants containing hormetic phytochemicals into daily and weekly routines.

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Here is another, newer Mattson paper [1] published in Scientific American this month on the hormesis effect - i.e. the modestly toxic phytochemicals in plants we eat stresses our cells and upregulates our natural defenses, improving our health.


Here is the full text courtesy of Al Pater:






Mattson MP.
Sci Am. 2015 Jul;313(1):40-5. No abstract available.

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  • 3 months later...



Here is a new, well-written popular press article titled Fruits and Vegetables Are Trying to Kill You on the complex relationship between reactive oxygen species (ROSs) and health.


It talks about how exercise increases ROS levels, which triggers an increase in endogenous antioxidants to quench them, but how single antioxidant supplements may counteract this upregulation of the body's own defenses thereby doing more harm than good. It has a good discussion of hormesis, and Mattson is extensively quoted about xenohormesis - that by eating plants that contain high levels of defensive plant chemicals (phytochemicals), we're leveraging these plant signalling compounds to bolster and/or upregulate our own defenses against stresses and intruders.


Worth reading for anyone interested in why plants are healthy, and why supplements may not replicate those benefits.



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Thanks Dean, interesting article.  I would just make one comment:  He says that plants contain "trace amounts of naturally occurring pesticides".  It would have been closer to the truth to have said:  "massive amounts of naturally occurring pesticides."  One paper I referenced on the email list here a couple of years ago found that as much as 5% of the weight of many plants are plant-engineered pesticides. 


In addition, that that is around 10,000 times as much as the residues of human-engineered pesticides found on agricultural produce in stores; and that the chemical structure of both are remarkably similar   ........  Humans have discovered in the past one hundred years what plants have discovered over millions of years - certain rather specific types of chemicals are effective at killing, or deterring, pests of one kind or another.  If the archives were available I am fairly sure I could locate that discussion.






"The unverified conventional wisdom is almost invariably mistaken."

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