The Vitamin B12 requirement is small but essential. Vegans can include the source of vitamin B12 in their diets. Nutritional Yeast is a restorative in general, both in specific cases and in deficiency states. This yeast should not be confused with so-called brewer's yeast, which is normally obtained from waste from the industrial manufacture of beer, dehydrated at high temperatures and added with flavors. This nutritional yeast is not activated, when it speaks of deactivated yeast, it means that when it is mixed with water or sugar, the natural fermentation process does not begin.