What does yucca do to ammonia? Some people say with ammonia probs people should take yucca with protein meals which may help keep ammonia levels down? How does this work?

Yucca root is rich in soap-like molecules known as saponins.  Saponins bind with ammonia for excretion.  Yucca saponins are also used for odor control in poultry and pig farms also by binding ammonia.