Does spermidine actually do anything against ageing?

Spermidine extends lifespan in yeast, worms, fruit flies and mice. This has been demonstrated across multiple independent experiments, both by administering the substance and by genetically blocking its production. The mechanism largely revolves around autophagy: the cellular cleaning process by which cells clear away damaged material. Without spermidine this process largely breaks down, even when you fast or restrict calories. Spermidine is therefore an indispensable link in the way fasting extends lifespan.

For the heart, there is evidence from mouse studies that spermidine has a protective effect. Population research in humans shows that people who obtain more spermidine through their diet die less often from cardiovascular disease. This is an association, not proof that spermidine is the cause.

For the brain the picture is similar. A large prospective study found that people with a higher dietary intake of spermidine developed cognitive impairments less often. In aged mice, spatial learning and mitochondrial function in the memory centre of the brain improved. Here too, causal evidence in humans is not yet available.

The major caveat is that no large completed clinical trial in humans exists yet. All human evidence is observational: people who eat more spermidine through their diet do better on certain outcomes, but this could also be because such people lead a healthier lifestyle in general. Clinical trials are still ongoing. Moreover, several principal investigators in this field have financial interests in companies that sell spermidine products. This makes independent confirmation especially important.

In the EU, spermidine as a supplement is only permitted in a specific form: wheat germ extract, with a maximum of approximately 6 mg of spermidine per day. This is a so-called novel food authorisation, meaning that other sources or higher doses are not permitted in the EU. Anyone considering a supplement would do well to check whether the product meets these requirements. Products that fall outside this framework are formally not permitted in the EU.

If you want to increase your intake through food, spermidine occurs naturally in wheat germ, aged cheeses, mushrooms and legumes. Whether a supplement offers anything extra beyond a varied diet for healthy people has not been proven at this time.