It, like beetroot (which comes in powder form if, like me, you absolutely loathe beetroots), increases the nitrous oxide in the blood. This appears to be the effective agent. So I have a banana daily, and a drink made from beetroot powder, turmeric, and ginger. The drink is supplemented by some drinking chocolate and chilli for taste, occasionally some mixed spice. I did try some garlic powder, but it is too smelly for others in close proximity! However, garlic is also a very good source of Nitrous Oxide and hence good for BP.
I keep a daily eye on the BP, but I also find that I am usually too low on salt - I can taste the few occasions when that happens - and only then out comes a veggie oxo cube. Not a veggie, but I do like the taste.