The Huffington Post (among many others) reported today that scientists have found that ‘young blood’ reverses the effects of aging in mice.  After being injected with blood from younger mice, older mice got stronger, exercised longer, learned more, and performed better mentally than mice given older blood.  This might be, as the research indicates, because of the abundance of a protein called GDF11 which appears to decline with age.  Read more about the study here.