It took me three years to beat my yeast problem down, so it is a process. You can allow yourself to cheat sometimes but it is better to make your food choices which say yes to you and NO to yeast. Letting yeast win is not saying YES to you and it does have repercussions that as you age will become more problematic. So its your health or your inner child squeaking for a cookie...ggg. There is a way to find balance by becoming sensitive to your body. I use mycostat which I buy from the Herbal Healer Academy. http://www.herbalhealer.com
You can find their candida protocol online there.
I have used oregano oil and olive leaf extract to kill yeast, as well, Essiac
to support the liver and kidneys while they detox the dead debris. You need to find balance in cleansing too so there is no healing crisis. I dealt with this by doing a round of the protocol and then doing an equal round of rebuilding my blood and gut flora. If you get it under control, your cravings eventually grow weaker. Also my naturopath would tell me, eat something sweet and then take the medicine since you have to *lure* some of the yeast from where they hide in the different organs.
For me, seeing the yeast in my blood in full living color during a dark field study was the best motivation. Also if you spend major bucks on supplements, without killing off the yeast, you are wasting so much money giving the yeast and the parasites
the best of your good intentions.
Now about your grapefruit seed (extract??)question, I do not see any problem with an extract. I used bach flower rescue remedy (drops) under my tongue on some of my days I felt particularly fuNky. I would not recommend any pills or supplements though. Improving your digestion and then later replacing the flora with a quality probiotic is akin to weeding your yard and filling in the holes so the weeds wont come back. The cleanse does not kill the yeast, but does slough off their front porches!
Best of Luck on your healing path,