A study questions the role of taurine in slowing aging.

In 2023, a study published in the journal Science made taurine seem like an elixir of youth. The work of an international team of scientists showed that blood levels of this amino acid decline with age, that adequate levels improve immune system function, and that, although taurine occurs naturally in the body and can be consumed through meat, fish, or dairy products, it's possible to reap its benefits by taking supplements. In an experiment with mice, those given taurine lived up to 12% longer—the equivalent of eight human years—and had stronger muscles, less obesity, and less depression.

This work led the usual mix of doctors and influencers to begin recommending this amino acid as a supplement to reverse aging and the ailments that accompany it, but a new study suggests the link isn't so straightforward. Today, the journal Science publishes a second study , this time led by Rafael de Cabo, head of the Department of Translational Gerontology at the National Institute on Aging in Baltimore, USA, which questions those results.

Among other things, the scientists found that taurine does not decrease with aging in healthy individuals and, in fact, increases in some groups, such as human females or monkeys of both sexes. Therefore, there is no clear relationship between blood taurine levels and aging, and much greater variation in the amino acid is seen between individuals than is observed within a single individual over their lifespan. Furthermore, the relationship between circulating taurine and the markers used to measure health was inconsistent and varied by context. This calls into question the value of taurine as a biomarker of aging.

The contradictory results are partly explained by how the studies were designed. In the 2023 study, led by Vijay Yadav, then working at Columbia University, samples were taken from different individuals at a specific time, like a still photo, and then compared between groups. The snapshots of younger individuals were compared with those of older individuals, and conclusions were drawn. In the case of the De Cabo team's study, groups of mice, monkeys, and humans were followed throughout their lives, taking samples multiple times to understand the circumstances that cause taurine levels to vary and to avoid assuming that the level of a 25-year-old at one point, for example, cannot be very different if circumstances change a few days later.

The new study doesn't rule out the potential benefits of taurine in slowing aging, but its authors believe further studies will be needed to understand who may benefit and when. Yadav, now at Rutgers University, said in a press conference this week, in which he participated alongside the researchers of the study that partially refutes their results, that he doesn't recommend any taurine supplementation in the general population until more information is available. To obtain this information, the researcher is conducting a randomized, placebo-controlled trial with people around 60 years old who take this type of supplement.

In that same presentation, De Cabo warned that taurine is "a metabolite that is very sensitive to different physiological conditions" such as chronic or acute inflammation or in the context of fasting. "This is something that is easily understood with glucose. Depending on when you measure it, you'll have values ​​ranging from 300 to 60. It's an indicator of a physiological state that makes it difficult to decide how or why to give a supplement," the researcher continued. "I think that in the context of a clear deficiency, a lot of data is emerging that suggests you can make adjustments and produce beneficial effects," he concludes.

Yadav agrees that the glucose example can serve to maintain hope that taurine could be a useful biomarker. Forty years ago, blood sugar meters had similar problems, because the same individual's glucose level depends on factors that vary throughout the day. "But the system has been refined over time, and now it helps us determine whether or not there is a diabetic or pre-diabetic state," he explains. Luigi Ferrucci, co-author of the study, also emphasizes that variability in a blood marker "is normal" and may even be the rule for any biomarker. "Other metabolites can show variations of tenfold up or down at different times of the day," says Ferrucci, noting that this lack of stability is not unique to taurine.

In aging studies, this wouldn't be the first time that benefits have been observed in animals with some interventions that later have minimal or no effect when tested in humans. In animal models, taurine deficiency worsens health and shortens life, and supplements can prolong it. In humans, supplements are generally helpful for people with deficiencies due to specific problems, but not for healthy individuals. Ferrucci states that, in the current state of knowledge, "there is no supplement that improves longevity" and recommends, as simple as it is difficult, a balanced diet, "because if you have a balanced diet, everything you need is there."