Boosterspice is a drug compound originally believed to have been developed by genetic engineers on Jinx from a native ragweed. I was later revealed that it most likely was created by the UN using the Tree-of-Life that was recovered from Phssthpok's ship. It interrupts the aging process in humans. Typically used once someone starts reaching middle-age, one course of treatment lasts 25 years and regular treatment results in the user's apparent age stopping at the chronological age when treatment begun.
Originally it was rare and expensive for most of humans. Very few people are allergic to it but those who are were restricted to "natural lifespans;" although they still benefited from medical and alloplastic enhancements.