Black Pepper

Other names: Piper nigrum

In Vitro study: Extracts from black pepper leaf inhibit 5alpha-reductase (5AR)

Mouse study: Black pepper extract has ambiguous sexual effects

Mouse study: Black pepper extract considerably raises testosterone, and sperm count, but only slight boost to sperm motility
Subjects: 27 male Swiss albino mice, divided into 3 groups.
Groups: Control, black pepper water extract, black pepper alcohol extract
Delivery method: Black pepper extracts put into edible mouse pellets.
Found: More serum testosterone, more sperm, but not more sperm motility (that latter is apparently a DHT dependent process - see testosterone-vs-dht).