Does Green Tea Break Autophagy?

If you fast to trigger autophagy, it’s fair to ask whether your morning cup of green tea gets in the way. The honest answer is that nobody has tested it in people, so any firm rule you’ve read is a guess.

What is autophagy?

Autophagy is a process inside cells that clears damaged parts and misfolded proteins and recycles the material. A 2018 review of fasting and calorie restriction describes it as lysosomal, meaning it runs through the cell’s recycling compartments.

Does fasting really switch it on in people?

That review calls fasting and calorie restriction among the strongest non-genetic triggers of autophagy, and it concludes that both raise it in many tissues. The abstract doesn’t separate human studies from animal ones, though, so it can’t tell you how this plays out in people.

A 2022 study gives a sense of how tricky the human data are. Mice that did intermittent fasting showed higher autophagy markers in the liver, but not in muscle. In the human part, 50 women (average age 51) did 24-hour fasts three days a week for 8 weeks. In their muscle samples, one marker rose after a 24-hour fast. After a 12-hour overnight fast, several markers fell in the group eating 70% of their energy needs. The authors thought weight loss likely explained the drops.

None of this gives a fasting time at which autophagy starts in people, so we won’t give one. Be wary of any page that does.

What do we know about tea and autophagy?

EGCG is the main catechin in green tea, making up 50 to 80% of its catechins. Lab studies, mostly in cultured cancer cells and a few in mice, show it can change autophagy. A 2022 review of that cancer research points out two limits:

• The amounts used on cells (usually 1 to 100 micromoles per liter) are hard to reach in a living body. When green tea catechins are taken by mouth, blood levels peak in the sub- or low-micromolar range.
• The review says catechins are poorly absorbed and unstable, and it calls for better formulations before future in vivo studies and clinical trials.

That is cell work, not people drinking tea. We found no trial in which people drank green tea and had autophagy measured. So it isn’t known whether a cup of tea nudges autophagy up, down or not at all.

Does green tea break a fast?

It depends on what “break” means.

• Calories: Twinings says tea on its own has no calories. Sugar, honey and milk do, so those are what change a plain cup.
• Autophagy itself: untested. The lab findings don’t show that a cup of brewed tea would switch it off.

Rules like “tea is fine, matcha is not” are conventions in the fasting community. We found no study behind them.

What about matcha?

Matcha is made from the whole tea leaf ground into a powder, so you swallow the leaf rather than just what dissolves in water. We found no autophagy research on matcha either. If you want the full comparison, see how matcha differs from green tea.

Things to keep in mind

• Skip the extracts. NCCIH says green tea as a drink has no reported safety concerns for adults, but liver injury has been reported with extract tablets and capsules. Don’t take extracts to try to boost autophagy.
• Mind the caffeine. Mayo Clinic lists about 29 mg in 8 oz of brewed green tea, and says up to 400 mg a day may be safe for most adults.
• Ask first if you have a health condition or take medicine. Changing when you eat can matter. A clinician who knows your history can advise you.

More on how tea fits different diets is in our green tea health guides, including whether you can drink green tea on a carnivore diet.