What is mTOR and why does it matter in ageing?

mTOR is a molecular switch inside your cells that tracks how much nutrition and energy is available. When there is enough, mTOR tells the cell to grow and produce new proteins. That is useful when you are young and still growing, but when mTOR stays chronically overactive it contributes to accelerated cellular ageing and age-related diseases such as cancer, diabetes and heart problems.

The strongest evidence for mTOR's role in ageing comes from mouse studies using rapamycin, a drug that inhibits mTOR. Female mice lived an average of 249 days longer, male mice 154 days longer. That is one of the most robustly demonstrated findings in ageing research. Rapamycin already exists and is approved for use in humans as an anti-rejection drug after organ transplants, but whether it is safe enough as an anti-ageing agent in healthy people is still being investigated. Clinical trials are under way, but whether this will ever become standard care cannot be said at this point.

Eating less, particularly fewer calories or less protein, is the most practical way to reduce mTOR activity. In animal models this has been well demonstrated, and in humans there are indications pointing in the same direction. AMPK, a kind of energy meter inside your cells, acts as a natural counterweight to mTOR: when AMPK switches on in response to an energy deficit, it dials down mTOR activity. Exercise and periods of fasting activate AMPK in the same way.

Curcumin (the yellow compound in turmeric) and metformin (a diabetes drug) also inhibit mTOR, but for both the evidence in humans is still thin. Curcumin has been examined mainly in laboratory and animal research; metformin is currently being tested in a large trial called TAME, but results are not yet available. It would not be fair to recommend either of these agents now purely on the basis of their effect on mTOR.