(From an email newsletter. "Nick Norwitz MD PhD from StayCurious Metabolism" at substack

This hypothesis — that garlic-derived compounds might have longevity-enhancing effects — isn’t coming out of thin air. There’s a scientific rationale.

Garlic contains compounds called diallyl sulfides (DAS). DAS can boost levels hydrogen sulfide (H2S)— the same smelly gas responsible for rotten egg stink and... bad farts. (Yes, I said what I said.)

But weirdly enough, H2S acts like a hormone— a gas hormone — capable of diffusing through cell membranes and triggering signaling pathways throughout the body.

And, in long-lived animal models, increased H2S production is a recurring theme.

H2S signaling even appears essential for mediating the stress-resilience benefits of caloric restriction, one of the most robust interventions in aging research.

And, in other animal studies, H2S donors have shown benefits ranging from improved insulin sensitivity to neuroprotection and even enhanced physical performance.

When it comes to associations in humans, lower circulating levels of H2S are observed in people with obesity and diabetes — groups known to be at higher risk of pathological aging. And increased garlic consumption has been associated with reduced all-cause mortality in people as well.

No one of these puzzle pieces is conclusive, but together they start to shape an interesting picture.

Let’s get on to these new data…

Lifespan and Healthspan in MiceIn this new study, researchers fed mice a diet supplemented with DAS, the H2S precursors found in garlic.

The control group had a median lifespan of 787 days (white survival curve), as expected. But the DAS-treated mice lived significantly longer, reaching a median of 877 days (purple survival curve)— an 11.4% increase in longevity.

To be clear, this does not mean we should expect the same percentage increase in human lifespan. Lifespan extensions tend to shrink as you move up the evolutionary ladder — from worms to flies to mice to humans. But interventions that extend lifespan in animals often improve healthspan in humans.

Indeed, DAS supplemented mice performed significantly better on locomotor and neurocognitive tests: they had stronger grip strength, held on longer in the wire hang test (below, left), and performed better on memory assessments.

DAS, acting as a H2S donor, didn’t just add days to life — it improved the quality of those days. 

In the rest of this letter, available to StayCurious Metabolism Premium subscribers, we dig into the real meat of the story:

The metabolic benefits, including effects on glucose regulation and liver health

The underlying mechanisms — from gene expression changes to inflammation and more

The human data: a cohort of 288 people

Two practical tips to get the most out of your garlic.

A big-picture view of what all this means...