Does quercetin work against ageing and inflammation?

Quercetin is a substance that occurs naturally in vegetables, fruit and herbs. There has been scientific interest in its possible anti-ageing and anti-inflammatory effects for some time. However, the positive signals come almost exclusively from laboratory and animal research, such as studies in worms. Evidence in humans is scarce and cause-and-effect relationships have not yet been demonstrated.

The best-described effect is the reduction of inflammation. In laboratory and animal research, quercetin influences important inflammatory pathways and NAD+ metabolism. However, a well-designed human study showing that quercetin lowers measurable inflammatory markers is lacking. The step from the laboratory to a living human being is a large one.

For skin ageing, there is one laboratory study using human skin cells. Quercetin, in combination with another substance, strengthened protective effects through improved functioning of the cell's 'power plants' and cellular clean-up processes. However, that study comes from researchers employed by cosmetics company LG H&H, which means there is a commercial interest in positive outcomes. And it involves cells in a dish, not real skin.

In laboratory tests, quercetin has also been studied as a reference point when testing substances that inhibit ageing-related enzymes. Quercetin shows activity in these tests, but in one study a newly developed material performed even better. This confirms activity in the laboratory, but says nothing about how it works in the human body.

Through cell research, 70 proteins have been identified that quercetin binds to directly, including proteins involved in inflammation and cell growth. This provides useful insight into the mechanism of action. However, the clinical significance remains entirely unclear. Eat a varied diet of vegetables and fruit as good sources of quercetin; do not start supplementing on the basis of this early-stage research.