If they called for volunteers to be part of the trial that didn't test for any of the illnesses being assessed then I would volunteer. But I don't think that they include that category of person in a double blind test, lol.
Would you volunteer for a test like this one, where eating a plum, or drinking plum juice is all that you had to do? (That is, the testees no doubt wouldn't probably know which variety of plum they were eating/drinking.)
This seems like a safe test to me. Not that I know what on earth that I'm talking about!