While yeast served on its own probably isn't a staple in your diet, you likely eat at least one of the three common dietary types -- baker's yeast, brewer's yeast and nutritional yeast. Some people consume yeast as a dietary supplement, add it to recipes and, of course, use it in baking. There is no evidence to suggest that dietary yeast is bad for healthy adults -- in fact, it has some nutritional benefits.
Derived from a fungi called Saccharomyces cerevisiae, brewer's yeast is the most common type used as a dietary supplement. It's also used to make beer. Brewer's yeast is particularly rich in the B vitamins thiamine, riboflavin, niacin, pantothenic acid, pyridoxine, folate and biotin. B vitamins help your body convert carbohydrates, fats and protein to energy. Brewer's yeast is also high in the minerals chromium and selenium. Chromium plays a role in helping the body maintain a healthy blood sugar level, while selenium plays a role in thyroid hormone production.
Yeast in Baking
Baker's yeast is the same species, but a different strain than brewer's yeast. Even though this strain of yeast contains some nutrients, it's not particularly rich nutritionally, and thus is not used as a dietary supplement. Instead, it's used as a leavening agent to make dough rise in baking. It contains some trace minerals and is rich in folate. Yeast works by consuming sugar in the dough and excreting carbon dioxide and ethanol, causing air bubbles to form in the dough. This process is known as fermentation.
Nutritional yeast is sold in various forms such as flakes, powder and liquid, and it adds cheesy flavor and nutritional value to your meals. Nutritional yeast contains B-complex vitamins and selenium. Unlike brewer's yeast, it is sometimes fortified with B-12. Its B-12 content makes it especially beneficial to vegans, since B-12 only occurs naturally in animal-derived foods, like meat, that aren't allowed on a vegan diet.
Word of Caution
Yeast may interact with certain medications, so talk to your doctor before supplementing. Avoid taking yeast supplements if you're prone to yeast infections or if you have a weakened immune system due to disease or medication. If you take medication to control your blood sugar, while taking brewer's yeast, your glucose level may drop below normal. Discuss this potential interaction with your health care provider. He may need to monitor you or adjust your medication.