Study Could Help Explain Why Colder Body Temperature Extends Lifespan in Many Species

From ice baths and cold showers to whole-body cryotherapy, cold exposure has long been hyped as a wellness shortcut. The supposed benefits include boosted dopamine, weight loss, stronger immunity, or even slower aging.

Scientific evidence for these claims is scant, but a telltale link between temperature and longevity has intrigued scientists for over a century. Lowering ambient temperature by just a smidge can extend lifespan in the roundworm C. elegans, fruit flies, and even mice. Plenty of mechanisms could explain the curious effect, but scientists are still largely in the dark.

A new study may shed some light on the matter. When scientists grew roundworms at moderately cold temperatures, the worms steadily ramped up production of BH2, a helper agent for many enzymes, including those that build brain chemicals. Though initially produced in our muscles, BH2 roams to other parts of the body too, including the intestines and brain. Here, in the study, it boosted tyrosine production and contributed to a longer lifespan.

Mapping a longevity pathway in worms isn’t just about satisfying scientific curiosity. When the scientists supplemented human cells with BH2 or tyrosine, the treatments fended off toxic protein clumps associated with neurodegenerative diseases.

But don’t go ordering tyrosine just yet. A biological response in cells doesn’t automatically translate into a health benefit, especially one as complex as slowing aging. While worms are a useful model in longevity studies, they’re a far cry from humans. That said, an existing drug used to treat a metabolic condition can tweak the pathway, and examining clinical data from patients taking the drug could offer a useful test to see if the mechanism holds up in people.

More broadly, the findings point to muscles as active players in the aging process. Beyond movement, their chemical output could change how other tissues age. The findings “highlight the muscle’s ‘metabolome’—its full set of metabolites—as a potential source of signals that promote longevity,” wrote Hanseul Lee and Seung-Jae Lee at the Korea Advanced Institute of Science and Technology, who were not involved in the study.

Cold Case

As time ticks by, basic cell functions gradually falter. DNA’s protective end caps, called telomers, fray. Mutations accumulate in our genetic blueprint. Chronic inflammation flares across the body. Senescent “zombie” cells bathe healthy tissues in a toxic chemical brew. Cellular energy factories and waste disposal plants begin to sputter.

Dubbed the hallmarks of aging, these processes only partly depend on genetics. Environment, social factors, and lifestyle—diet, exercise, exposure to toxins—also shape our aging trajectory.

Temperature seems like an odd addition to that list. Yet nature is littered with examples. Hibernating mammals generally live longer than those who don’t. Yellow-bellied marmots, for example, spend up to seven months a year hibernating, lowering their body temperature and throttling metabolism. Scientists have found their biological aging essentially stalls during hibernation.

These observations inspired the rate-of-living theory, which suggests that the lower a creature’s metabolic rate, the longer it lives. Recent work has given the century-old idea a nuanced update by exploring how cooler temperatures directly activate mechanisms that counter some of the hallmarks of aging. But there are caveats.

Take mitochondria, our cells’ energy factories. With age, they become increasingly dysfunctional. A chill activates brown fat, which is packed with mitochondria, ramping up energy use and potentially overall metabolic health. In a small study of a dozen people exposed to mild cold for up to eight hours, most showed signs of better blood sugar regulation. But these were short-term effects, not evidence for lasting protection. Cold can also boost mitochondrial numbers, though whether they protect against aging in humans remains to be seen.

The immune system may also respond to a chill. A study in healthy people and those with inflammatory disease, found cold exposure slashed immune molecules called cytokines, which often fuel inflammation. A different study found lower temperatures slowed the accumulation of reactive oxygen species (little “bullets” that damage cellular components, including DNA).

A cellular waste removal plant, the proteasome, also seems to benefit from air conditioning. In 2023, David Vilchez at the University of Cologne and colleagues found that moderately cold temperatures boosted proteasome activity in both C. elegans and human cells. The newly invigorated cleanup crew chomped proteins known to aggregate into clumps involved in neurodegenerative diseases.