Amazingly, a compound contained within farts called hydrogen sulfide — responsible for the rotten-egg scent of a stinky fart — can actually be good for your health. So, not only is the act of farting a normal, natural, and relieving thing to do, but getting a whiff of that yucky odour can actually pay off in the form of health benefits. That is what the original article said, and it is the claim that has travelled furthest — and been most misunderstood — since the original research was published.

In a study performed at the University of Exeter, researchers found that inhaling small amounts of this gaseous compound had protective properties against damage of cell mitochondria and even against cancer. The mitochondria are the "powerhouse" of cells. Preventing or reversing mitochondrial damage is a key strategy for treatments of a variety of conditions such as stroke, heart failure, diabetes and arthritis, dementia, and ageing. Mitochondria determine whether cells live or die, and they regulate inflammation. Dysfunctional mitochondria are strongly linked to disease severity.

The study was published in the journal *Medicinal Chemistry Communications*, and a follow-up study, published in *The Nitric Oxide* journal with collaborators from the University of Texas Medical Branch, also found that the compound selectively prevented damage to the mitochondria.

That is an accurate summary of what the original article reported, but it needs a careful correction, because the way the story was reported in the press went far beyond what the researchers actually found. This is a good example of why reputable sources matter, and why this expanded article returns to the primary research and to the University of Exeter's own press release, rather than repeating the headline.

The Exeter research, led by Professor Matt Whiteman of the University of Exeter Medical School and Dr Mark Wood, did not study people smelling farts. It did not study farting at all. It studied a laboratory-made compound called AP39, which slowly delivers very small amounts of hydrogen sulfide specifically to the mitochondria inside cells. The researchers found that when stressed cells in a laboratory dish were treated with AP39, their mitochondria were protected and the cells stayed alive. In the University's own words: "We have exploited this natural process by making a compound, called AP39, which slowly delivers very small amounts of this gas specifically to the mitochondria. Our results indicate that if stressed cells are treated with AP39, mitochondria are protected and cells stay alive."

That is a promising early finding, but it is a long way from a health tip. First, the experiments were done in cells in a laboratory, not in people. Second, the hydrogen sulfide was delivered in tiny, controlled amounts directly to the mitochondria, not inhaled from the air. Third, hydrogen sulfide is toxic in larger amounts, and deliberately inhaling it is dangerous. The researchers themselves, and later commentators, have stressed that there is no indication that getting hydrogen sulfide from an outside source, such as smelling farts, benefits cell function. The Faculty of Medicine at the University of British Columbia put it plainly in a review of the story: there is "absolutely no indication that getting it from an outside source, like from smelling farts, benefits cell function."

So what is the real science? Hydrogen sulfide is a gas that our bodies produce naturally, in small amounts, as a signalling molecule. When cells become stressed by disease, they draw in enzymes to generate minute quantities of hydrogen sulfide. This keeps the mitochondria working and allows cells to live. If this does not happen, the cells die and lose the ability to regulate survival and control inflammation. That is why researchers are interested in hydrogen sulfide as a potential treatment: if they can deliver it in a controlled way to the right place inside cells, it might protect mitochondria in conditions where they are under stress.

The Exeter team designed AP39 to do exactly that. It is a mitochondria-targeted hydrogen sulfide donor. In laboratory studies, it protected mitochondria in blood vessel cells under stress, and in models of cardiovascular disease, more than eighty percent of the mitochondria survived under otherwise highly destructive conditions when AP39 was given. Early indications in small-scale studies also suggested that AP39 could reverse blood vessel stiffening and lower blood pressure in animal models. A follow-up study, published in *Nitric Oxide* with collaborators from the University of Texas Medical Branch, found that the compound selectively prevented damage to mitochondrial DNA.

Later research has continued in the laboratory and in animal models, including studies of AP39 and a related compound, AP123, in cells exposed to high blood sugar, and studies of AP39 in models of kidney injury, heart attack, and stroke. Those studies are still preclinical, which means they have not yet been tested in large human trials. The Exeter researchers have said they are working towards advancing the research to a stage where it can be tested in humans, but there is no approved treatment based on AP39, and no timetable for one.

That distinction — between a promising laboratory compound and a proven treatment — is essential. It is also why this article does not repeat the claim that smelling a fart is good for you, or that it can prevent cancer, stroke, or dementia. The original article's headline was catchy, but the science does not support it. What the science does support is more modest and more interesting: our bodies make hydrogen sulfide for a reason, mitochondria matter for health, and targeted delivery of tiny amounts of hydrogen sulfide in the laboratory can protect cells under stress. That is a genuine advance in understanding, and it may one day lead to new therapies. It is not a reason to seek out farts, and it is certainly not a reason to inhale hydrogen sulfide deliberately.

There is a related claim that sometimes appears alongside this story: that farting reduces high blood pressure and improves heart health. That claim is not supported by the Exeter research either. The Exeter research found that AP39, in laboratory and animal models, could lower blood pressure and reduce blood vessel stiffening. It did not find that farting does so, and it did not study people who fart frequently. Passing gas may feel relieving, and it can reduce bloating and abdominal discomfort, but it is not a treatment for high blood pressure or heart disease. If you have high blood pressure, the proven steps are those recommended by the NHS, the American Heart Association, and the World Health Organization: reducing salt, eating a balanced diet, being physically active, maintaining a healthy weight, limiting alcohol, not smoking, and taking prescribed medicines as directed.

The hydrogen sulfide story is a reminder to read health news critically. A press release headline, a social media post, and a laboratory paper can tell three different stories. When you see a claim that sounds too good, or too strange, to be true, check the source. Ask: was this studied in people, or in cells or animals? Was the substance given in a controlled dose, or inhaled from the environment? Was the outcome a real health benefit, or a change in a laboratory marker? Reputable sources — the NHS, the Mayo Clinic, Cleveland Clinic, the National Institutes of Health, and the original research papers themselves — will usually make those distinctions clear.

When Gas Is a Sign to See a Doctor

Most gas is normal, and most of the time it needs no medical attention. But there are patterns that should prompt a visit to your doctor, and it is important to know them, because early investigation can make a real difference for conditions such as coeliac disease, inflammatory bowel disease, and, rarely, bowel cancer.

Cleveland Clinic advises seeking medical care as soon as possible if you fart and have abdominal pain and cramps, bleeding from your anus, diarrhoea, fever, unintentional weight loss, or a skin rash. The NHS advises seeing a GP if self-help and pharmacy treatments have not worked and flatulence is affecting your life, and it lists symptoms that may point to constipation, IBS, coeliac disease, or lactose intolerance. The Mayo Clinic advises seeing a doctor if gas or gas pain is persistent, severe, or accompanied by other symptoms.