Jerusalem Post

ByWALLA! HEALTH

A study found that a smelly substance called hydrogen sulfide, which is also found in gas, improved brain function by 50% in mice with Alzheimer’s. Is this an excuse to smell your own farts?

There’s almost no topic that invites more viral headlines than the combination: Gas and Alzheimer’s. But behind the amusing headlines about “smelling your own farts to protect the brain” stands a very serious study, coming from one of the world’s leading medical centers – Johns Hopkins in the U.S.
The researchers there examined the effect of hydrogen sulfide (H₂S) – the gas that causes the “rotten egg” smell in gas – on the aging brain in a mouse model of Alzheimer’s. Their conclusion is interesting: In low and controlled levels, hydrogen sulfide may protect brain cells and slow Alzheimer-like processes. But it’s important to clarify right now:
This does not mean you should start intentionally smelling farts – and certainly not expose yourself to high concentrations of the gas, which can be toxic and dangerous.

What did the researchers discover?
Our body already produces tiny amounts of hydrogen sulfide as part of normal cellular activity. This gas has important roles in intercellular communication and in regulating various processes, including in the brain.

In a study published in 2021 in PNAS, Johns Hopkins researchers created a mouse model of Alzheimer’s:
• The mice were genetically engineered so that their brains mimic changes characteristic of Alzheimer’s in humans.

• They received treatment with NaGYY – a donor molecule that gradually releases hydrogen sulfide into the cells.
This was not “smelling gas,” but a controlled pharmaceutical substance injected into the body.
Over 12 weeks the researchers tested:
• Spatial memory (whether the mice remember where a platform is located in water)
• Motor function and physical activity
• Brain changes at the level of proteins and biochemical processes.

The results:
• The mice that received the H₂S-releasing molecule showed about a 50% improvement in cognitive and motor measures compared to untreated Alzheimer’s mice.
• Their brains showed more normal activity of a key enzyme called GSK3β, which is directly connected to the tau protein – the protein that forms “tangles” in nerve cells and contributes to brain damage in Alzheimer’s.
• When hydrogen sulfide levels were normal, it appeared that GSK3β was “diverted” from excessive interaction with tau, reducing the tendency of tau to form toxic clumps.
In addition, the researchers showed that a chemical process called S-sulfhydration – the attachment of sulfur groups to proteins – drops significantly in the aging brain and in the Alzheimer’s brain. Restoring hydrogen sulfide to a “healthy” level helped reconstruct some of the sulfhydration and improve cellular function.
So what’s the connection to farts?
Gas in the digestive system is produced partly by the activity of gut bacteria, and some of the unpleasant odor indeed comes from hydrogen sulfide.
But:
• The study did not use gas originating in the gut, but an internal cellular mechanism to produce/receive H₂S in a controlled level.
• High concentrations of H₂S are extremely toxic to tissues, especially to the lungs and brain.
• Smelling gas is not a therapeutic method and is not approved or safe – it’s just a colorful angle loved by the media.
In other words: Our bodies know how to use very small amounts of hydrogen sulfide for cellular communication and protection. That does not mean the bottom line is “smell your farts and you’ll prevent Alzheimer’s.”
Why is this important for Alzheimer’s research?
Alzheimer’s is a complex neurodegenerative disease involving, among other things:
• Beta-amyloid protein deposits
• Tau protein tangles inside nerve cells
• Chronic inflammation in the brain
• Mitochondrial dysfunction (the cell’s power stations)
• Reduced ability of cells to clear waste.
Work on hydrogen sulfide joins a series of studies showing that biological gases (such as NO, CO, and H₂S) function as “signaling molecules” in the brain.
The researchers claim that maintaining normal H₂S levels in brain cells may:
• Protect nerve cells from oxidative damage
• Maintain normal activity of key enzymes (like GSK3β)
• Reduce the formation of tau tangles
• And perhaps slow some of the processes that lead to cognitive decline.
This is still far from a “cure,” but it provides a new direction for potential therapeutic targets – for example, donor drugs designed to release H₂S in precise doses and in the right locations in the brain.
What does this mean for us, humans?
At this stage – not much in practical day-to-day terms. It’s important to understand:
• This is a mouse study in an experimental model.
• There is still no approved treatment in humans based on H₂S injection.
• Any human trial, if conducted, will require strict safety testing, because the margin between a “beneficial” dose and a toxic dose may be narrow.
What can we take from this?
• It again highlights how complex maintaining brain health is and how many delicate chemical factors are involved.
• The study strengthens the understanding that our body produces substances that seem “strange” or “smelly,” but have important, deep roles.
• And it hints that future medicine may include more treatments based on “biological gases” in controlled doses.
Until that happens, the well-known recommendations for preventing dementia remain as strong as ever: Physical activity, Mediterranean diet, good sleep, balancing blood pressure and lipids, quitting smoking, protecting hearing and vision, and maintaining social life and an active brain.