For most people, there's no need to remove yeast-containing foods solely out of concern for gut health. It helps, though, to know what form of yeast you're eating and what else is in the food.
Baker's Yeast and Bread
Baker's yeast helps dough rise by fermenting sugars and producing gas. Most of the yeast is killed during baking, but yeast components remain in the finished bread.
Bread can be part of a balanced eating pattern. If it leaves you feeling uncomfortable, that doesn't prove yeast is responsible. The type of grain, other ingredients, portion size and what you eat alongside it can also matter.
Sourdough is made with a culture that includes yeast and bacteria. Its taste and texture differ from other breads, but sourdough isn't automatically yeast-free or guaranteed to agree with everyone.
Nutritional Yeast
Nutritional yeast is a deactivated yeast sold as flakes or powder. It has a savory flavor and can be added to foods such as soups, popcorn and roasted vegetables. Because it isn't alive, it isn't a probiotic and won't multiply in your gut.
Some nutritional yeast products are fortified, meaning nutrients have been added. Others aren't, so check the label if you're choosing one for a particular nutrient. The amount of fiber and other nutrients can also differ between products.
You don't need nutritional yeast for a healthy gut, but it can be a useful seasoning if you enjoy it. Try a small amount with a familiar meal and notice how it agrees with you.
Brewer's Yeast and Fermented Foods
Brewer's yeast is associated with fermentation, the process microorganisms use to change sugars and other components in food or drinks. Brewer's yeast products are also sold as supplements, so check whether a particular product is intended as a food ingredient or a supplement.
Fermented foods aren't all alike. Their ingredients, preparation and whether they contain live microorganisms vary. A food made with fermentation isn't automatically a probiotic, and its effects can't be assumed to match those of a studied supplement.
Key Takeaway: The word "yeast" doesn't tell you whether a food contains live organisms, what nutrients it provides or how you'll respond to it.