Some claim that transfusions with "young blood" from teenagers can reverse the aging process.

It's being tested in patients over the age of 35 as part of a clinical trial called ambrosia, where people paid $8,000 to get the rich growth factors found in bloods plasma platelets.

"There are pretty much people from most states, people from overseas, people from Europe and Australia," Dr. Jesse Karmazin said.

Results of the trial have not been published.

Dr. Karmazin, who plans to open a business selling young blood, says patients who've had it say they feel amazing, and he says he's seen evidence of reversing the aging process in rats.

"Their brains are younger, their hearts. Their hair, if it was gray, it turns dark again," he said.

There has also been encouraging Alzheimer's research using young blood at Stanford University.

"We found that it was safe and feasible to administer infusions of young plasma weekly," Dr. Sharon Shaw, an Alzheimer's researcher at Stanford, said.