Calories and Nutritions in Yeast

A 100-gram serving of dry yeast or instant yeast contains 325 calories.

A 1-kilogram (1000g) portion of dry yeast or instant yeast contains 3250 calories.

One packet of dry yeast or instant yeast, weighing 7 grams (0.25oz), contains 23 calories.

The health benefits of yeast are associated with nutritional yeast and specific yeast-based supplements, not the small amounts of baker's yeast used for leavening. These specialized yeasts are packed with vitamins, minerals, and antioxidants. The health benefits are detailed below.

• Rich Source of B Vitamins Nutritional yeast is an excellent source of B vitamins, including thiamin, riboflavin, niacin, B6, and B12 (in fortified versions). These vitamins are crucial for energy metabolism, nerve function, and the formation of red blood cells. A study on the effects of B vitamin supplementation highlighted their role in reducing stress and improving mood. (Stough, C., et al., 2011, The effect of 90 day administration of a high dose B-complex on work stress).
• Supports Immune Function Certain compounds found in yeast, such as beta-glucans, have been shown to enhance immune system activity. Beta-glucans are polysaccharides that can modulate both the innate and adaptive immune responses, potentially reducing the incidence and severity of infections. A clinical trial demonstrated that daily intake of a yeast-derived beta-glucan reduced the number of common cold episodes in healthy subjects. (Talbott, S. M., & Talbott, J. A., 2012, Baker's Yeast Beta-Glucan Supplement Reduces Upper Respiratory Symptoms and Improves Mood State in Stressed Women).
• Provides High-Quality Protein Nutritional yeast is a complete protein, meaning the substance contains all nine essential amino acids that the human body cannot produce on its own. This makes the substance a valuable protein source, especially for individuals following vegetarian or vegan diets. The protein quality of various food sources is well-documented, with yeast protein being recognized for its high biological value. (Combs, G. F., Jr., 2012, The Vitamins: Fundamental Aspects in Nutrition and Health).

The potential downsides of yeast are related to specific health conditions, such as yeast allergies or overgrowth, rather than the consumption of yeast in food for most people. The table below shows the potential downsides of yeast.

• May Trigger Migraines Yeast-containing foods, such as aged cheeses and freshly baked bread, are known to contain tyramine, a compound that can trigger migraine headaches in susceptible individuals. Tyramine is formed from the breakdown of an amino acid as foods age. A review of dietary trigger factors for migraines lists yeast extract and freshly baked yeast goods as common culprits. (Martin, V. T., & Behbehani, M. M., 2001, Ovarian hormones and migraine headache: a review of the evidence).
• Can Cause Allergic Reactions Although rare, some individuals can have an allergic reaction to yeast (Saccharomyces cerevisiae). Symptoms can range from hives and digestive upset to more severe reactions like anaphylaxis. Diagnosis is confirmed through allergy testing. (Novembre, E., et al., 1997, Allergy to the yeast Saccharomyces cerevisiae in a child).
• Potential for Intestinal Overgrowth (Candida) While baker's and nutritional yeast are different species from Candida albicans, some health practitioners advise individuals with Candida overgrowth or compromised immune systems to avoid all yeast products as a precaution. The concern is that the body may react to similar proteins or that the presence of dietary yeast could exacerbate an existing imbalance in the gut microbiome. (Gaby, A. R., 2011, Nutritional Medicine).

Yes, certain types of yeast, particularly nutritional yeast and specific probiotic strains, are good for a person's health due to their dense nutritional profile and functional compounds. For digestive health, the fiber in yeast, especially beta-glucan, acts as a prebiotic, feeding beneficial bacteria in the gut and supporting a healthy microbiome. A specific probiotic yeast, Saccharomyces boulardii, has been shown in numerous studies to be effective in preventing and treating diarrhea, including antibiotic-associated diarrhea (McFarland, L. V., 2010, Systematic review and meta-analysis of Saccharomyces boulardii in adult patients). For brain health, the abundance of B vitamins in nutritional yeast is critical. These vitamins, especially B6, B9 (folate), and B12, play a vital role in homocysteine metabolism, and elevated homocysteine is a risk factor for cognitive decline and neurodegenerative diseases (Smith, A. D., et al., 2010, Homocysteine-lowering by B vitamins slows the rate of accelerated brain atrophy in mild cognitive impairment: a randomized controlled trial). For immune function, yeast-derived beta-glucans have been found to enhance the body's defense mechanisms. A clinical study showed that supplementation with baker's yeast beta-glucan reduced the incidence of upper respiratory tract infections and improved mood in stressed individuals (Talbott, S. M., & Talbott, J. A., 2012, Baker's Yeast Beta-Glucan Supplement Reduces Upper Respiratory Symptoms and Improves Mood State in Stressed Women).

The calorie content of yeast changes based on its form and processing, due to differences in moisture content. The highest calorie types are the dehydrated forms, active dry yeast and instant yeast, which both contain 29 calories per tablespoon (9 grams). These yeasts have most of their water removed, concentrating the calories. The lowest calorie type is fresh yeast, also known as cake yeast, which contains only 9 calories per tablespoon (9 grams). The high moisture content of fresh yeast dilutes the caloric density. Nutritional yeast, which is also dehydrated but sold in light flakes, falls in the middle, with about 20 calories per tablespoon.

The origin of yeast in food production is ancient, dating back to at least the early Egyptians around 4,000 BCE. The discovery was likely accidental, when wild yeast, which is present in the air and on the surface of grains and fruits, naturally inoculated a batch of dough or a grain-based gruel. The microorganisms began to ferment the sugars, producing carbon dioxide gas that caused the dough to rise and alcohol that transformed the gruel into a primitive beer. The Egyptians mastered this process, using sourdough starters (a symbiotic culture of yeast and bacteria) to consistently leaven bread, creating a much lighter and more palatable product than the flatbreads that preceded the substance. This knowledge of leavening spread throughout the ancient world, with the Romans becoming skilled bakers. For centuries, brewers' yeast (barm) from beer making was the primary source for bakers. The scientific understanding of yeast began in the 19th century with Louis Pasteur, who identified Saccharomyces cerevisiae as the living organism responsible for fermentation. This discovery paved the way for the isolation and commercial production of pure yeast strains, leading to the development of granulated active dry yeast and instant yeast in the 20th century, which revolutionized baking by providing a stable, reliable, and convenient leavening agent for households and industries worldwide.