Ibuprofen can banish headaches and soothe throbbing joints, but the drug may have another benefit. A new study shows that it increases longevity in lab organisms, raising the possibility it does the same thing in people.

Researchers used to scoff at the idea of extending life span, but it turns out to be surprisingly easy—at least in organisms such as mice and worms. Drugs that prolong survival of these creatures—aspirin and the antidiabetes compound metformin, for example—are already in many of our medicine cabinets. Several studies suggest that ibuprofen is also worth a look. Ibuprofen suppresses inflammation, which underlies many age-related diseases and might contribute to aging itself. In addition, people who take ibuprofen for a long time have a lower risk of developing two age-related illnesses, Alzheimer’s disease and Parkinson’s disease, several analyses found.

To put ibuprofen through its paces, biochemist Michael Polymenis of Texas A&M University, College Station, and colleagues gave yeast, nematode worms, and fruit flies doses of the drug that are comparable to what humans would take. The life spans of all three types of organisms increased if they received ibuprofen, the researchers report today in PLOS Genetics. In yeast, for instance, ibuprofen stretched life span by 17%, half of what researchers can produce by cutting the cells’ food supply (another approach to increasing longevity). Worms survived about 10% longer on the drug, and flies gained about the same amount.

But it’s not obvious why ibuprofen would benefit these organisms. The drug stems inflammation in people by blocking cyclooxygenase enzymes, which help synthesize inflammation-promoting molecules. Yeast and nematodes don’t have these enzymes, however, and they don’t suffer from inflammation.

A clue may come from a previous study that showed the drug poisons yeast that can’t make the amino acid tryptophan, which cells need to manufacture proteins. Polymenis and colleagues found that tryptophan levels declined in yeast cells exposed to ibuprofen. They also showed that the drug spurs destruction of a protein that enables cells to absorb tryptophan.

Ibuprofen doesn’t have a huge impact on tryptophan levels, though, decreasing them by about 15% to 20% in the yeast. To explain how this modest drop in tryptophan concentration promotes longevity, the researchers invoked a counterintuitive mechanism. Numerous studies have found that instead of killing organisms, moderate amounts of stress—such as intermediate doses of radiation or toxic chemicals—actually increase life span. A mild tryptophan deficiency triggered by ibuprofen might work in the same way, the researchers speculate. “We figure it’s one more type of stress that seems to be conducive to life span,” Polymenis says.

“They convincingly show that ibuprofen prolongs life span in these model organisms,” says molecular biologist Ellen Nollen of the University of Groningen in the Netherlands. She doesn’t find the evidence of tryptophan’s involvement as persuasive, noting that the drug changed levels of several amino acids in yeast cells. Ibuprofen could also promote longevity through its effects on these molecules, she says.

“There are two new good ideas here,” says gerontologist Richard Miller of the University of Michigan, Ann Arbor, who is one of the participants in the U.S. National Institute on Aging’s Interventions Testing Program (ITP), in which researchers at three institutions are gauging whether a variety of compounds alter the life spans of mice. One is the revelation that “some anti-inflammatory drugs that people are taking may have beneficial effects that are unrelated to inflammation,” he says. The other is the possible involvement in the aging of proteins that transport amino acids into cells, which could lead researchers to new ways to tweak life span.

Nollen and Miller say the study supports testing ibuprofen in mice. The ITP did assess a related drug, nitroflurbiprofen, and found no change in longevity. However, Miller notes, those results don’t rule out studies on ibuprofen because the two drugs are slightly different.

So far, researchers haven’t shown that any drug extends human life span. To folks who are impatient, Miller cautions against extrapolating the study’s results, especially because the side effects of long-term ibuprofen use can include fatal stomach bleeding. “I think any person who says, ‘Anything that works in yeast is something I want to take,’ is asking for trouble.”