If you live in the UK before talking to others about your idea you need to get them to sign a Non-disclosure agreement. Link below for further info.
https://www.gov.uk/government/publications/non-disclosure-agreementsI've no idea what the US use, but it will be something similar you will need to do some research before discussing your ideas.
I am nowhere near US. and this place got no such laws & regulation to secure anything.
NDA's do secure things very well. They can be in multiple countries if written right. But if you pick someone bad yes... they might break NDA.
So pick well known trusted people. But US,UK,China, etc all follow NDA's.