Blood Lust of the Tupinamba (c) 1975 by Jim Hines.
Appeared in Forbidden Knowledge #1, published by Last Gasp, 1978.
This is not fiction, and it is not for the easily disturbed. We don’t know exactly Jim Hines did his research, but a German Soldier named Hans Staden was almost a victim of this cannibalistic ritual. He published a book about it in 1557 after returning to Europe. You can find out more about the Tupinamba, or Tupis, of Brazil on Wikipedia.
– Copies of Forbidden Knowledge #1 & #2 are still available from Last Gasp.