Yeast, a single-celled fungus, plays a diverse role in nature and human applications, from baking to brewing. It is found in various environments, including soils and on plant surfaces. With over 1,500 recognized species, the question of whether yeast can be safely consumed raw often arises due to its different forms and functions.
Understanding Different Types of Yeast
Different types of yeast are cultivated for distinct purposes, and their processing determines whether they are active or deactivated. Baker’s yeast (Saccharomyces cerevisiae) is a live and active form used as a leavening agent in bread. It converts sugars in dough into carbon dioxide, causing the bread to rise. This active yeast is sold in various forms, including fresh compressed cakes, active dry granules, and instant yeast.
In contrast, nutritional yeast and brewer’s yeast are typically deactivated forms of Saccharomyces cerevisiae. Nutritional yeast is specifically grown for its food properties and then heated and dried to render it inactive, meaning it cannot cause fermentation. Brewer’s yeast, often a byproduct of beer brewing, is also processed to be inactive for consumption as a supplement. This deactivation ensures the yeast cells are no longer living or active.
Why Raw Baker’s Yeast Poses Risks
Consuming raw, live baker’s yeast carries risks due to its active nature. When ingested, the live yeast can continue its fermentation process within the warm, moist environment of the digestive tract. This internal fermentation generates carbon dioxide gas and alcohol. The production of carbon dioxide can lead to uncomfortable symptoms such as bloating, excessive gas, and stomach cramps.
While rare, this internal fermentation can cause auto-brewery syndrome, where an overgrowth of fermenting fungi or bacteria produces intoxicating amounts of ethanol from ingested carbohydrates. For individuals with compromised immune systems, consuming live yeast might increase the risk of fungal infections, such as candidiasis. However, for most healthy individuals, the stomach’s acidic environment can often inhibit the extensive growth of ingested baker’s yeast.
Safe and Beneficial Forms of Yeast
Nutritional yeast and brewer’s yeast are safe to consume raw because they are deactivated. This means their cells have been killed during processing, eliminating their ability to ferment and cause digestive issues within the body. These forms of yeast are valued for their rich nutritional profiles.
Nutritional yeast is a good source of plant-based protein, containing all nine essential amino acids. It is particularly notable for its high content of B vitamins, including thiamine (B1), riboflavin (B2), niacin (B3), pyridoxine (B6), and often fortified with vitamin B12, which is especially beneficial for those on plant-based diets. It also provides trace minerals such as zinc, selenium, manganese, and molybdenum. Nutritional yeast has a distinctive savory, cheesy, or nutty flavor, making it a popular ingredient sprinkled on popcorn, pasta, salads, or used in vegan cheese sauces and dips.
Brewer’s yeast also offers a range of nutrients and is a source of B vitamins, protein, and minerals like chromium, selenium, iron, and zinc. The chromium content in brewer’s yeast may contribute to maintaining healthy blood sugar levels. It is considered a probiotic and may support digestive health. Brewer’s yeast can be incorporated into the diet in powder, flake, or tablet form, mixed into smoothies, juices, or yogurt.