I like to know this as well but i could not yet find any conclusive source about it. I grew up with the idea that the whole plant was toxic. Hower i look like an interesting plantgroup - stacks lots of functions - N-fixer, bee-friendly, bird-friendly edible fruit, ..... BUT considered a class II exotic - may become invasive here. I would like to know whether the plant leaves are edible (herbal tea ?) for humans and if there are proven medicinal properties (side effects ....).
Perhaps somebody in Kew gardens knows more ? They used to have this 'incr edible' festival but i cannot find recent quotes on that. Whoever organised that might get us somewhere. Helas my netconnection is miserable today, so i'm shutting down for now.
This are the best (english) treads i found on short notice