Selenium yeast is a nutritional supplement created by growing the common baker’s yeast, Saccharomyces cerevisiae, in a medium rich in the trace mineral selenium. This process results in the yeast cells metabolically incorporating the inorganic selenium into organic compounds. This organic form mimics how selenium is naturally processed by plants and enters the human food chain.
How Selenium Yeast is Produced
The creation of selenium yeast begins with a controlled fermentation process using a selected strain of Saccharomyces cerevisiae. Inorganic selenium, typically selenite or selenate, is introduced into the growth medium and absorbed by the yeast cells.
Once inside the cells, the selenium is converted through metabolic pathways for sulfur-containing amino acids. The selenium atoms structurally substitute for sulfur in the amino acid methionine, resulting in the formation of selenomethionine. The final product is a dried, inactivated yeast containing selenium primarily as selenomethionine, differentiating it from inorganic supplements.
Bioavailability Compared to Inorganic Forms
Bioavailability refers to the proportion of a nutrient that is absorbed and utilized by the body. The organic form of selenium found in selenium yeast, selenomethionine, is recognized and handled by the body much like the common amino acid methionine. This structural similarity allows selenomethionine to be absorbed very efficiently in the small intestine, often reaching an absorption rate of around 90%.
Unlike inorganic forms, such as sodium selenite, selenomethionine can be non-specifically incorporated into the body’s protein stores in place of methionine. This storage capability, particularly in muscle tissue, means the selenium is retained for a longer period and is available to the body for future use. Conversely, inorganic selenite is absorbed less efficiently, and any surplus that is not immediately used is quickly excreted, primarily through urine.
Studies show that organic selenium from yeast leads to greater blood selenium concentrations that are sustained over a longer period compared to selenite. The increased bioavailability means it is a more effective way to improve overall selenium status in the long term. Furthermore, the organic form is less toxic than the inorganic forms.
Key Biological Roles of the Mineral
Selenium is an essential trace element required for numerous biological functions in the human body. Its primary role is to serve as a component of special proteins known as selenoproteins. These selenoproteins are enzymes that contain the selenium-containing amino acid selenocysteine at their active site.
One of the most recognized functions involves antioxidant defense, primarily through the action of glutathione peroxidase (GPx) enzymes. The GPx enzymes require selenium to neutralize harmful reactive oxygen species and peroxides, thus protecting cells from oxidative damage.
Selenium is also required for the proper metabolism of thyroid hormones. A group of selenoproteins called iodothyronine deiodinases are responsible for converting the inactive thyroid hormone (T4) into its active form (T3). Without adequate selenium, this conversion process is impaired, which can affect overall thyroid function. Selenoproteins are also involved in immune response and DNA synthesis.
Safe Consumption Parameters
Because selenium is a trace mineral, the body requires only small amounts, but consistent intake is necessary to maintain health. The Recommended Dietary Allowance (RDA) for selenium in adult men and women is set at 55 micrograms (\(\mu\)g) per day. Pregnant and lactating women have slightly higher requirements.
It is equally important to be aware of the maximum safe intake to avoid toxicity. The Food and Nutrition Board (FNB) has established the Tolerable Upper Intake Level (UL) for adults at 400 \(\mu\)g per day. Consistently exceeding this limit can lead to a condition called selenosis.
Early signs of selenosis often include hair loss, nail brittleness or discoloration, and mild gastrointestinal upset. Anyone considering a selenium supplement, especially one as concentrated as selenium yeast, should first consult with a healthcare provider to ensure their total daily intake remains within the safe parameters.