Its a risk you take, for sure, but there are ways to limit that risk.

Non-disclosure agreements are the first thing that come to mind but many really hate signing them especially when you're looking for their support.

If you have the funds, patent your idea. Provisional patents are a possibility where the cost of a full patent are prohibitive. Check the regulations in your state.

Research the people you're going to be talking to. Do they have a professional reputation? Are they known to be people of integrity?

Make sure you document every step of the process from concept to every significant discussion that's been had around it.