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GLOSSARY · CELLULAR PATHWAY

Autophagy

The cellular self-eating process. Cells use autophagy to break down and recycle their own damaged proteins, malfunctioning organelles, and intracellular invaders — including some viruses.

Edited by M. Callahan · Last reviewed 2026-05-10

How researchers study it

The molecular machinery of autophagy was identified in yeast genetics screens by Yoshinori Ohsumi in the 1990s. He received the Nobel Prize in Physiology or Medicine in 2016 (Nobel Foundation, 2016). The pathway involves a conserved set of ATG (autophagy-related) proteins that nucleate a double-membrane structure, expand it around cargo, seal it into an autophagosome, and deliver it to the lysosome.

Three main forms are recognized: macroautophagy (the canonical pathway), chaperone-mediated autophagy, and microautophagy. Macroautophagy is the most studied. It is triggered by nutrient deprivation, growth-factor withdrawal, oxidative stress, hypoxia, and intracellular pathogen detection. A central regulator is the mTOR kinase: high mTOR activity (well-fed, growth signals on) suppresses autophagy; low mTOR activity (fasting, stress) releases the brake (Mizushima & Komatsu, Cell, 2011).

In viral infection, autophagy can degrade viral components and present viral peptides to immune cells — but many viruses have evolved to manipulate the pathway. SARS-CoV-2 has been shown in cell-culture work to interact with autophagy components (Miao et al., Developmental Cell, 2021, PubMed 33231974). Whether dietary or pharmacological induction of autophagy alters post-viral recovery in humans is an open research question — model-system data is suggestive, but human trials are limited.

Common misconceptions

"Fasting always triggers autophagy in humans the same way it does in mice."Human autophagy data is harder to come by — measuring it directly in humans requires tissue biopsy and is rarely done in dietary studies. Most claims about "hours to autophagy" extrapolate from animal models.
"More autophagy is always better."Both deficient and excessive autophagy are linked to disease. The system is regulated for a reason.
"A specific supplement turns on autophagy."Spermidine, resveratrol, and others have been reported to induce autophagy in cells or animals. Human clinical evidence on whether they meaningfully shift autophagy in vivo at supplement doses is preliminary.
WHAT THIS DOES NOT MEAN This entry describes a cellular pathway. It is not a recommendation for any specific fasting protocol, supplement, or "autophagy-boosting" product. Fasting and any major dietary change should be discussed with a clinician, particularly for people with diabetes, eating disorder history, or pregnancy.
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SOURCES
  1. Nobel Foundation. "The Nobel Prize in Physiology or Medicine 2016." nobelprize.org
  2. Mizushima N, Komatsu M. "Autophagy: renovation of cells and tissues." Cell, 2011. PMC4868821
  3. Miao G et al. "ORF3a of the COVID-19 virus SARS-CoV-2 blocks HOPS complex-mediated assembly of the SNARE complex required for autolysosome formation." Developmental Cell, 2021. PubMed: 33231974
Informational only · Not medical advice This entry describes a cellular process studied in biology. It does not diagnose, treat, cure, or prevent any disease, and it does not endorse any dietary protocol. Medical and dietary decisions belong with a licensed clinician.