So I have an idea for a health food product / or 'dietary supplement'
(subject to FDA approval  -- it's complicated)   It's a very simple
recipe for something quite yummy and highly nutritious.  In running
this idea past consultants, potential manufacturers and the like, it's
very difficult to talk about it without giving away the ingredients. 
I know it is recommended and prudent to have each person sign a
confidentiality agreement, but really . . . what is to prevent them
from telling their best friend's brother, who mentions it to his
cousin, who has a pal already in the business, who lives two thousand
miles away, and who jumps on the idea like a dog on a bone?

Looks to me like a confidentiality agreement is a formality at best .
. . what can really give it teeth?


***

Coca-cola never said what was in their product for years and years?

You need to play up the mystery, decide what you can say, and only say that.

Some lawyer can easily you give a document with teeth, but only a fool
would sign it.

Well, it allows you to sue for breach of contract, so if you can't
make money with your product, you can make some by suing.