Brewers yeast isn't itself a calmer. It does however contain B vitamins that are helpful in replenishing the B vitamins that are "lost" due to stress. You can find it at any health food store. Some "calming" herbs that can be used are chamomile, vervain, lemon balm, hops, passion flower, valerian. Again you should be able to find these at your local health food store and hopefully they sell bulk bags. But I don't believe in using anything too long term. Try using one herb for a month of two and then you should be able to start "weaning" off.