I drink the yeast, and was pre diabetic before starting to home brew. Last checkups are all very good. I then did some research and found the following- but, yes some folks are very sensitive to the yeast and react badly with killer headaches:
Quoted from: http://vitamins.lovetoknow.com/Healt..._Brewers_Yeast
Brewer's yeast is a byproduct of the beer industry. It absorbs vitamins and nutrients from the other ingredients involved in the brewing process. As the yeast absorbs nutrients it also absorbs flavors, which are often bitter. Some companies use a process to remove the bitterness from the product but often this also removes some of the nutritional content. In fact, during this process nearly all of the chromium will be removed. If you choose to use this type of brewer's yeast, you should add a chromium supplement.
Brewer's yeast is found in health food and natural food stores. There is no way to know the exact nutritional content in any brewer's yeast because it will vary according to the age of the yeast and even from batch to batch.
Brewer's yeast has a high nucleic acid count. This is an important component of cell development. Other vitamins and minerals contained in brewer's yeast are:
It is low in calories, fat, sodium and carbohydrates, which makes it great for the person who has dietary restrictions for health reasons.
Some Health Benefits of Brewer's Yeast:
Using brewer's yeast daily as a supplement to your healthy diet can improve the following conditions:
Repels fleas when given to household pets
"If you use brewer's yeast to help control diabetes, be sure you get the type that has not gone through the debittering process. The nutrient in the yeast that helps with diabetes is chromium, the supplement that is removed during debittering. Chromium is also the part of the yeast that helps lower LDL (bad) cholesterol and raise HDL (good) cholesterol. The chromium in brewer's yeast is more bio-available, allowing the body to use it more effectively than the type found in supplements.