What does your klotho level say about how fast you are ageing?

Klotho is a protein produced mainly in the kidneys that plays an important role in regulating minerals in your body, including phosphate and vitamin D. Its level in your blood declines as you get older. That pattern has been confirmed across dozens of studies, but there are no exact cut-off values on which you could say 'you are ageing too fast'.

The push to use klotho as an ageing marker originally came from mouse studies: mice without a functioning klotho gene display features that resemble premature ageing. That is compelling animal research, but the direct translation to humans has not been proven. Additional tissue studies in mammals show that klotho deficiency disrupts primarily the energy metabolism of cells (the mitochondria), rather than the inflammatory pathways that also play a role in ageing. Those findings are not human findings either.

In humans, the association is clearest in kidney disease. Even in the early stages of chronic kidney disease, klotho drops measurably while another hormone that regulates phosphate (FGF23) rises. That pattern is seen as an early signal of kidney and cardiovascular problems. Klotho as a marker has its strongest clinical support here, but that is different from saying it measures your general rate of ageing.

Associations have also been described between low klotho and a greater risk of cardiovascular disease, brain diseases and certain cancers. But these are associations, not proven causal relationships. Klotho has also been proposed as part of a measurement panel for frailty in older adults, but that proposal has not yet been clinically validated. Clinically usable threshold values do not exist.

Exercise does not demonstrably raise your klotho levels. A small study in people in their sixties with an elevated Alzheimer's risk found no change in klotho levels after six months of aerobic training.