The evidence consistently points to declining sirtuin activity contributing to age-related damage to the liver, kidneys, blood vessels and bones. That mechanistic link is well-supported biologically and has been partially confirmed in humans. But whether sirtuins can be effectively boosted through supplements such as NAD+ boosters or resveratrol, and whether that actually delivers meaningful health benefits in humans, remains uncertain for now: the clinical studies are still missing.
Sirtuins are a family of seven enzymes (designated SIRT1 through SIRT7) that act as a kind of cellular maintenance team: they help repair DNA damage, keep chronic inflammation in check, and regulate metabolism. They depend on NAD+, a substance whose levels in the body decline as we age. Multiple studies show that sirtuin activity falls with ageing, and that this goes hand in hand with greater disease burden and faster physical decline.
The strongest human evidence comes from research into organ damage. In older people with alcohol misuse, the activity of the enzyme SIRT1 in white blood cells was measurably lower than in younger people, and precisely that group had the most severe liver inflammation. That pattern was found in both human blood and mouse experiments. In kidney function decline too, researchers see altered sirtuin signalling as a contributing mechanism, although the precise cause-and-effect relationship there has not yet been proven.
In animal models the effects are more striking. Mice in which SIRT3 was artificially increased via gene transfer developed less bone marrow stem cell ageing and less age-related osteoporosis. The underlying mechanism was improved clearance of damaged mitochondria, the energy centres of cells. These are, however, exclusively animal findings; whether the same occurs in humans is unknown. Likewise, laboratory and mouse studies showed that a substance called PDRN (derived from salmon sperm) inhibited SIRT1 breakdown in skin cells, but here too clinical evidence in humans is lacking.
An interesting new direction is the link with gut health. As people age, gut bacteria produce less acetate, a fatty acid that normally suppresses pro-inflammatory signals in blood vessel wall cells via SIRT1. Less acetate means less SIRT1 activity and more vascular ageing. Sodium acetate was proposed in this research as a possible therapy, but clinical studies in humans do not yet exist.
For activating sirtuins through supplements, such as resveratrol-like compounds or NAD+ boosters, the evidence in humans remains limited. Review articles acknowledge the potential for cardiovascular protection, but at the same time note that the chemical workings of sirtuins are still insufficiently understood and that robust clinical results are not forthcoming. Anyone taking sirtuin-activating supplements today in the hope of a longer life is getting ahead of evidence that does not yet exist.
Based on two review articles, four specific mechanistic studies (partly in humans, partly in animal and cell models) and one lab/animal model study. No large randomised clinical trials available as a source.