Polly: Any of us with an overgrowth of yeast are likely to need some extra B1. B1 is destroyed when the yeast toxin acetylaldehyde is detoxified. Also, candida can cause the breakdown of B1 before it has a chance to be absorbed by the intestines.  Those with mercury poisoning should pay particular attention to this vitamin. In *Ziff’s Dental Mercury Detox book, he states,
“The symptoms of B1 deficiency and mercury poisoning are almost identical.”
Mercury lowers B1 levels by oxidizing it. Since many of us are considering using lipoic acid to chelate mercury, it should also be noted that B1 is required to have lipoic acid work properly. 
If plain B1 doesn’t seem to help, try coenzyme B1 (also called TTFD). Dr. Teitlebaum notes that some of his fibromyalgia patients require the coenzyme form of B1.  DEWS and Allergy Research/Nutricology used to carry TTFD separately, but demand hasn’t been high enough to keep it as a separate nutrient. For now, you will have to look for it in a “coenzyme” or “coenzymate” B complex supplement. Source Naturals and DEWS make them. There is also another form of B1 available called allithiamine. This “fat-soluble” form of B1 is absorbed well. It is from Cardiovascular Research/Ecological Nutrients. Phone (800) 351-9429. There is also Benfotiamin or Befotiamine which is another fat soluble coenzyme form of B1.
Polly: If you have yeast overgrowth, there are many reasons that you may want to get extra B6, at least for a while.
1) You might be low on coenzyme B6 if you have been exposed to the yeast toxin acetylaldehyde.  This toxin interferes with the production of coenzyme B6.
2) You might be low on coenzyme B6 if you have been exposed to alcohol for a long period. Some types of yeast and bacteria produce alcohol.
3) Dr. Shaw, in his book on autism, suggests that starting B6 supplementation early in your treatment might reduce die-off symptoms. Since B6 is an aldehyde, its effectiveness may be diminished by the presence of the yeast toxin acetylaldehyde. For this later reason, Dr. Shaw suggests that the extra B6 might be particularly important during a yeast overgrowth condition, but might not be as critical after the yeast levels are reduced.
4) There may be a functional deficiency of B6 as well as the actual deficiency. When yeast levels are high, often there are high levels of arabinose. According to Dr. Shaw, this can cause a functional deficiency of B6, lipoic acid and biotin.
5) Pentosidine formation may be prevented by higher levels of B6, glutathione and vitamin C. (High levels of arabinose formed by yeast can lead to pentosidine formation. Pentosidines interfere with many functions in your body and might be a contributing factor in Alzheimer’s disease.)
6) B6 is important for both your cell-mediated immune response (Th1) and your humoral immune response (Th2). 
7) B6 is very important for the proper absorption of protein; protein is very important for your cell mediated immune response.  (It takes a while for the immune system to recover after a period of low protein.)
8) B6 and the other B vitamins are required to activate the liver enzymes that get rid of toxins.
For all of the above reasons, if you have yeast overgrowth, addition of B6 may be a wise investment, even if you don’t notice anything spectacular from it.
Mrs. Generic: Wonder if B6 has a more “bioavailable” form, just like pantethenic acid has the form pantethine?
Polly: Just like the active form of pantethenic acid is called pantethine, the active form of B6 is called coenzyme B6, or sometimes Pyridoxal-5-Phosphate or P5P. Coenzyme B6 is the actual form of the vitamin that the body needs. Coenzyme B6 is a much better purchase than plain B6, in my opinion.
1) I strongly suspect that many of us who have had a long-standing yeast problem may have trouble converting B6 into its coenzyme form. You need the amino acid alpha-ketoglutaric acid and vitamin B2 to convert B6 into its active coenzyme form. Some of us may be low on alpha-ketoglutaric acid because the yeast toxin acetylaldehyde depletes this. 
2) Those with aluminum poisoning may be low on alpha ketoglutaric acid and have trouble using phosphates.  This could interfere with the formation of Pyridoxal-5-Phosphate (coenzyme B6) and riboflavin-5-phosphate (coenzyme B2).
3) Coenzyme B6 isn’t that much more expensive and, when you consider its effectiveness is considered 3 to 10 times higher, it is actually cheaper. *Country Life’s “Active B6“ contains coenzyme B6 and it costs about $8 for 50 capsules of 50 mg each. This should be enough to tell if it is helpful. *Solgar makes tablets of P5P (coenzyme B6). *Klaire Labs makes a combination of P5P with magnesium glycinate. You might have to have your vitamin shop order one of these for you.
4) Personally, I’d try the coenzyme form of B6 before ever trying the high dose B6. I think the coenzyme B6 product should be much less likely to cause nerve problems. The liver has a limited ability to convert B6 into coenzyme B6. If you overload the body with plain B6, the B6 can theoretically become toxic by taking up the receptor sites meant for coenzyme B6.  If B6 starts to cause nerve problems, doctors suggest that you lower the dose, and add magnesium and other B vitamins, especially B2. B2 activates an enzyme that completes the conversion of B6 into coenzyme B6.
Here are some brief articles on coenzyme B6.
Mr. Generic: How much coenzyme B6 or P5P should I take?
Polly: I was told to take 40 mg of coenzyme B6 three times per day (total of 120 mg) by the company that did my amino acid assay. In Dr. Shaw’s book on autism, they talk about using 500 mg or more of regular B6 along with B2 and magnesium. If you assume that coenzyme B6 is up to 10 times as effective as regular B6, this translates into 50 mg or more of coenzyme B6 per day. However, one must always be careful to observe reactions carefully and not take too much. Those with a PST problem must be particularly careful with coenzyme B6. Coenzyme B6 can suppress the PST enzyme, phenol-sulfotransferase.  (There is some more information about PST, B6, autism and attention deficit in book 5.)
Bernard Rimland, MD, suggests that in order to avoid destabilizing the coenzyme B6, you take your coenzyme B6 after your meals, especially if you are taking other vitamins and minerals before your meal. However, nothing is perfect. I have heard of one autistic kid who can’t tolerate the coenzyme B6, but who does well with plain B6. Part of the problem may be that the coenzyme B6 is used more quickly than plain B6. Of course, if you are taking prescription drugs, you should check for interactions before supplementing high doses of either form of B6.