As we age our blood changes Viacheslav Iakobchuk / Alamy Stock Photo

Could something in your blood be controlling how you age? The proteins in blood seem to undergo three waves of changes as we age, and can be used to determine a person’s biological age from a blood sample.

Blood proteins associated with youth could help us understand why young blood seems to rejuvenate older animals, and could hint at treatments for ageing, say Benoit Lehallier at Stanford University in California and his colleagues.

The first hints that something in blood might have rejuvenating properties came from experiments …