Does yeast contain gluten?

Baker's yeast and nutritional yeast do not contain gluten. Real brewer's yeast, which is a by-product of brewing beer, contains gluten. Other types of brewer's yeast, which are grown on a sugar medium, do not contain gluten.

Gluten is a protein found in grains. Although all grains contain gluten, only the gluten in wheat, barley, rye and oats tends to cause problems in people with gluten sensitivities. Yeast is a microscopic fungus and not a grain, so it is gluten-free. Standard brewer's yeast is not considered gluten-free because it grows on grains and is likely to be contaminated with trace amounts of gluten.