When people speak of the regenerative power of “young blood,” they usually mean it metaphorically. But a trio of new studies show that compounds in the blood of young mice can rejuvenate older animals in a number of ways–and suggest that same could possibly apply to humans. In some of the studies, blood from young mice flowed into older ones when their circulatory systems were directly connected; in another study, blood from youngsters, as well as a protein called GDF 11, was injected into elder rodents. In all cases, the older mice showed a number of improvements in health, almost as if they had become young again, as National Geographic reported:

The tranfusions also stimulated the growth of neurons in regions of the brain responsible for memory formation and a sense of smell. These mice were better able to distinguish between different odors, and remember how to navigate a maze, reversing declines in these abilities normally seen in the course of again.

But it is reasonable to think this won’t be some sort of silver bullet. Here is one important caveat, as noted in the New York Times: