Yeast

Yeast is used mainly for fermentation: leavening bread and pastries, producing beer and wine, and making other fermented foods. Nutritional yeast provides protein and B‑vitamins as a food additive. Specific yeast strains serve as probiotics (e.g., for diarrhea), and as industrial tools in biotechnology for producing enzymes, vaccines, insulin, biofuels and flavor compounds in food and pharmaceutical manufacturing.

Yeast are single-celled fungi that reproduce mainly by budding. Beneficial species, like Saccharomyces, are used in baking, brewing and fermentation. Some yeasts, such as Candida species, are normal body commensals but can overgrow and cause infections (oral thrush, vaginal yeast infections), especially when immunity is weakened. Diagnosis uses microscopy or culture; treatment involves topical or systemic antifungals.

Yeast is not inherently harmful—baker’s and brewer’s yeasts are safe and used in baked and fermented foods and supplements—yet some yeasts (Candida species) can overgrow and cause infections like thrush, vaginal candidiasis or systemic disease in immunocompromised people. Risk increases with antibiotics, diabetes, steroids or weakened immunity. Good hygiene, balanced diet and medical treatment when symptoms persist prevent or control problematic yeast overgrowth.

Yeast (Candida) normally lives on skin, in the mouth, gut and vagina. Infection occurs when it overgrows — often after antibiotics, pregnancy, high blood sugar, weakened immunity, hormonal changes, tight or damp clothing, or disruption of normal bacterial balance. It’s usually not sexually transmitted but can pass between partners. Good hygiene, controlling diabetes, and avoiding unnecessary antibiotics reduce risk.

Yeast—especially nutritional and probiotic strains—can benefit health. Nutritional yeast is a low‑fat, protein‑rich food loaded with B vitamins, fiber and trace minerals (often fortified with B12). Probiotic yeasts like Saccharomyces boulardii support gut health, helping prevent or shorten certain diarrheas and restoring balance after antibiotics. Fermentation by yeasts also improves digestibility and releases beneficial nutrients and bioactive compounds.

Make a wild yeast starter: mix equal parts whole-grain flour and lukewarm water in a clean jar until a thick batter, cover loosely and leave at room temperature. Every 12 to 24 hours discard half and feed with equal fresh flour and water. Within three to seven days you’ll see bubbles and a tangy smell—then it’s ready for baking. Discard if mold appears.