Hormesis

What it proposes

A biological stressor has a biphasic dose-response: low doses are beneficial (the organism adapts and becomes more resilient), high doses are harmful. This generalises across:

• Mitohormesis — mild ROS exposure activates antioxidant defences.
• Exercise — mechanical and metabolic stress drives adaptation (the entire framework of training).
• Heat (sauna) — heat-shock protein induction.
• Cold (cold exposure) — brown-fat, norepinephrine, mitochondrial biogenesis.
• Fasting — autophagy, ketogenesis, AMPK activation.
• Caloric restriction — the broadest hormetic intervention known.
• Hypoxia — HIF stabilisation, vascular and mitochondrial adaptation.
• Plant polyphenols — xenohormesis hypothesis: low-toxin exposure triggers stress responses.

Why it matters

Hormesis is the unifying mechanism behind most non-pharmacological longevity interventions. It also explains why naive antioxidant supplementation often fails or backfires: blunting the stress signal prevents the adaptive response.

Dose matters

There is no universal “hormetic dose”. Each stressor has its own curve. Going harder is not always better; over-training, over-fasting, and extreme cold exposure all sit on the harmful side.

Related entries

Free radical theory, Exercise, Caloric restriction, Sauna, Cold exposure.