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The amino acid taurine was once thought to decline with age, and animal research suggested that taurine supplements could delay ageing. But a new study shows that the decline doesn’t happen consistently. In fact, taurine levels tend to increase in people over time, suggesting that low levels of the nutrient aren’t a driver of ageing.

Previous research has shown that taurine concentrations decline in men as they age and that people with higher taurine levels at 60 years old tend to have better health outcomes. This, along with evidence that taurine supplements extend lifespan in mice and monkeys, suggested that low taurine contributes to ageing.

The trouble is that taurine fluctuates in response to other factors too, such as illness, stress and diet – therefore, declines in this key amino acid may not be due to ageing. at the National Institute on Aging in Maryland and her colleagues analysed taurine levels in 742 people between 26 and 100 years old. The participants, about half of whom were women, didn’t have underlying health conditions and provided three to five blood samples between January 2006 and October 2018.

On average, taurine levels were almost 27 per cent higher in women at 100 years old than at 26 years old and rose about 6 per cent in men between the ages of 30 and 97. Similar results were seen in 32 monkeys that underwent three to seven blood draws between 3 and 32 years of age. Between 5 and 30 years of age, taurine levels rose 72 per cent in female monkeys and 27 per cent in male monkeys, on average.

Together, these findings indicate that taurine levels are not a reliable indication of ageing. What’s more, taurine levels also varied widely between people and even within individuals over time, suggesting that other environmental factors influence them, says Fernandez.

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However, some people may still benefit from taurine supplementation, says Fernandez, pointing to studies that show it helps regulate blood sugar in people with type 2 diabetes or obesity. But whether it can delay ageing in otherwise healthy people is an open question.

at Rutgers University in New Jersey says he and his colleagues are currently conducting a clinical trial of taurine supplementation in middle-aged adults. “We hope to finish the trial by the end of 2025,” he says. “Hopefully it will generate sufficiently rigorous data to show whether or not taurine supplementation delays the pace of ageing in humans or increases health and fitness.”