Re: yeast extract

Doubtful. The early books on candida did warn to stay away from all yeast products because they were sure that it would bother the immune system. Once the immune system targets something as being bad, it tends to target any derivatives too. But then more and more people got candida, and they of course cheated on their diets, and didn't suffer any ill effects.

Lots of good things come from cultured yeast, some people are bothered by those, like certain B vitamins and probiotics. But a soap? doubtful.

You can side-step the issue altogether by getting a good castille soap. I like Dr. Bronner's myself. :)