What is mTOR and why does it matter in ageing?

mTOR is a protein complex found in every cell that acts as a kind of switch: it reads signals from the environment (are there enough nutrients? growth factors?) and then decides whether the cell should grow, produce proteins, or instead clear out cellular waste. That last function, the removal of damaged components, is called autophagy and is essential for keeping cells healthy.

When mTOR is overactive, that balance is disrupted. Cells keep growing when they should really be cleaning up and repairing themselves. This is increasingly linked to accelerated ageing, as well as to diabetes, cancer, and the breakdown of brain cells. More recent research also shows that mTOR works closely with the cell's powerhouses: when that cooperation falters, it has consequences for energy balance and cell survival, particularly in age-related diseases.

Fasting and protein restriction measurably lower mTOR activity. The same applies to restricting specific amino acids, such as methionine. This is probably one of the ways in which these kinds of dietary interventions could slow ageing.

The drug rapamycin directly inhibits mTOR and demonstrably extends the lifespan of mice. In humans, there are early positive signals: studies see favourable changes in the immune system, the cardiovascular system, and the skin. For muscles, hormones, and the nervous system, the same analysis found no effect, and for several other organ systems no human studies have yet been conducted. In people with age-related diseases, more infections and elevated blood lipid levels were reported, which are serious safety risks. In healthy individuals, the scarce available studies found no serious side effects, but these were investigated in small groups and without long follow-up. Always discuss rapamycin with a doctor; this is not a supplement you take on your own.