Green Tea: NMN’s Quiet Partner
What research on EGCG suggests about NAD⁺ recycling
TA Medical Research Team · 6 min read · Cellular Health
Green tea is so ordinary in Japan that it barely registers as a choice. It arrives with lunch, sits beside the keyboard in the afternoon, and is poured for guests before anyone asks.
Yet scientists studying how our cells make and recycle energy keep running into the same molecule from the tea leaf. And some of what they are finding connects directly to NAD⁺, the molecule at the centre of our recent articles.
A Quick Refresher
NAD⁺ powers our mitochondria, supports DNA repair, and declines as we age. NMN is one of the body's direct building blocks for it. In a University of Tokyo trial in men aged 65 and over, NMN raised blood NAD⁺ and was linked with better muscle strength and performance.
So NMN is the fuel. But an engine also needs machinery that makes, uses and recycles that fuel. That is where green tea comes in.
Meet EGCG
Green tea is rich in plant compounds called catechins. The most abundant and most studied is epigallocatechin gallate, or EGCG. Black tea and oolong contain far less, because their processing transforms most of the catechins. Green tea, steamed or pan-fired soon after picking, keeps them largely intact.
What Japan's Own Data Shows
The Ohsaki Study, led by Tohoku University and published in JAMA in 2006, followed 40,530 adults aged 40 to 79 for about eleven years. Those who drank the most green tea had a lower risk of death from all causes, with the clearest link to cardiovascular disease. Women drinking five or more cups a day had around 31% lower cardiovascular risk. Black tea and oolong showed no such pattern.
A note worth adding: in Japan, green tea is usually enjoyed alongside washoku, the traditional table of fish, miso, seasonal vegetables, seaweed and soy. That pairing is another layer worth exploring when we look at tea's benefits in the data. How green tea and washoku may work together would make a fascinating study, and one we look forward to seeing in the future. |
Inside the Cell: The Salvage Pathway
Your body does not build most of its NAD⁺ from scratch. It recycles it. Every time a cell uses NAD⁺ for repair or signalling, a by-product called nicotinamide (NAM) is left behind. The cell then runs it through a two-step recycling route, the salvage pathway:
Step 1 | The enzyme NAMPT converts nicotinamide into NMN. This is the slow, rate-limiting step, and it declines with age. |
Step 2 | The enzyme NMNAT converts NMN into fresh NAD⁺, ready to be used again. |
Supplemental NMN enters the loop just after the Step 1 bottleneck, supplying a building block for replenishing the NAD⁺ pool. But those building blocks still need the cell’s machinery to put them to work. This is where your daily cup of green tea becomes interesting: laboratory research suggests that EGCG may support some of the enzymes and signals involved in making and recycling NAD⁺. For those taking NMN, this offers a promising connection to explore. Let’s look at three places where EGCG may play a supporting role.
1. The step right after NMN
Researchers at Karolinska Institutet in Sweden, home of the Nobel Prize in Physiology or Medicine, reported that EGCG activates NMNAT2, a form of the enzyme that converts NMN into NAD⁺ in nerve cells. In their lab work, EGCG raised NAD⁺ in brain neurons. NMN delivers the raw material for Step 2, and EGCG appears to help switch on the enzyme that carries it out. It is early-stage research in cells, but a remarkably neat fit.
2. The bottleneck enzyme
EGCG activates AMPK, the cell's energy sensor, the same switch that exercise and fasting flip. A 2008 study from the U.S. National Institutes of Health found that activated AMPK was needed to increase NAMPT, the Step 1 bottleneck enzyme. In humans, exercise raises muscle NAMPT, and athletes carry roughly twice as much as sedentary people. No study has yet shown green tea raises NAMPT in people, so this remains a plausible connection rather than a proven one.
3. The engines that use NAD⁺
NAD⁺ does its work through sirtuins, often called longevity proteins, and through our mitochondria. In a 2017 Redox Biology study, EGCG raised NAD⁺ in a laboratory worm widely used in ageing research, boosted new mitochondria, and extended healthy lifespan. Those benefits depended on AMPK and SIRT1. And when sirtuins use NAD⁺, they release nicotinamide back into the salvage pathway, completing the loop.
What NMN provides | What EGCG may support |
Raw material for NAD⁺ | NMNAT2, which turns NMN into NAD⁺ (lab data) |
Enters after the slow step | AMPK, linked to the NAMPT bottleneck |
Raises blood NAD⁺ in human trials | SIRT1 and mitochondrial activity (animal data) |
The fuel | The machinery |
A Glimpse at the Brain
In 2025, a University of California, Irvine team published a study in GeroScience pairing these ideas almost exactly. They treated aged mouse brain cells with nicotinamide, which also feeds NAD⁺, together with EGCG. Within 24 hours, a key energy molecule returned to youthful levels and the neurons regained their ability to clear damaged proteins, including amyloid. The lead researcher stressed this was done in cells in a dish, but it shows scientists are now testing an NAD⁺ precursor and EGCG together.
The Twist: More Is Not Better
In the worm study, EGCG's benefits followed an inverted U-shaped curve. A moderate amount helped, and a larger amount helped less. EGCG seems to work by giving cells a gentle, beneficial challenge, much like exercise, rather than by flooding them.
Human safety data agree. In 2018, the European Food Safety Authority concluded that traditionally brewed green tea is generally safe, with typical drinkers taking in about 90 to 300 mg of EGCG a day. Concentrated supplements providing 800 mg or more a day, however, were linked to rises in liver enzymes.
The practical takeaway is reassuringly simple: enjoy green tea as a drink, the way Japan always has, rather than as high-dose extract capsules. |
A Simple Daily Habit
● If you already take NMN, pairing it with a morning cup of green tea is an easy habit to build.
● Enjoy two to four cups of brewed green tea across the day, ideally with or after meals.
● Brew with hot rather than cold water to draw out more catechins. Sencha steeped for a minute or two is a fine everyday choice.
● Keep your later cups earlier in the day if caffeine affects your sleep.
● Keep moving. Exercise activates the same energy sensor as EGCG and is proven to raise NAMPT in people.
If you have a liver condition or low iron, are pregnant, or take regular medication, please speak with your doctor before changing your tea or supplement habits. This article is for general information and is not medical advice. |
The Takeaway
NMN supplies the fuel for NAD⁺. Green tea may help keep the machinery that uses and recycles it in good working order. No study has yet tested the two together in people, but the science points in a consistent direction, and the habit is safe in sensible amounts. Next time you pour a cup, it may be doing more than you think.
References
Igarashi M, et al. Chronic NMN supplementation elevates blood NAD⁺ levels and alters muscle function in healthy older men. npj Aging, 2022.
Kuriyama S, et al. Green tea consumption and mortality in Japan: the Ohsaki Study. JAMA, 2006.
Karolinska Institutet. EGCG activates NMNAT2 and increases NAD in neurons (research summary).
Fulco M, et al. AMPK-mediated regulation of Nampt. Developmental Cell, 2008.
Costford SR, et al. Skeletal muscle NAMPT is induced by exercise in humans. American Journal of Physiology, 2010.
Xiong LG, et al. EGCG promotes healthy lifespan through mitohormesis in C. elegans. Redox Biology, 2017.
Santana RA, McWhirt JM, Brewer GJ. Treatment of age-related decreases in GTP levels restores endocytosis and autophagy. GeroScience, 2025.
European Food Safety Authority. Scientific opinion on the safety of green tea catechins. EFSA Journal, 2018.
