Selenocysteine is a rare amino acid that contains selenium and performs essential functions in the human body.
Due to its unique structure, it is incorporated into selenoproteins that are involved in antioxidant protection, regulation of metabolism, and maintenance of thyroid health.
Selenocysteine is considered the 21st amino acid and plays a key role in a number of biochemical processes that cannot be replaced by other substances.
Useful Properties
The main function of selenocysteine is to participate in the work of selenium-dependent enzymes, such as glutathione peroxidase and thioredoxin reductase, which protect cells from oxidative stress.
It also contributes to the regulation of thyroid hormone metabolism and supports normal immune system function. Due to these qualities, selenocysteine is important for the prevention of inflammatory processes, cardiovascular diseases, and immune disorders.
Daily Requirement and Sources
The recommended daily intake of selenium (as part of selenocysteine) is about 55 mcg for adults.
For pregnant and breastfeeding women, the requirement increases to 60–70 mcg.
The maximum allowable dose without the risk of toxicity is 400 mcg per day.
Selenocysteine is primarily obtained from animal protein, where it is incorporated into the structure of enzymes.
Main sources include:
- Brazil nuts (rich in selenium, a precursor of selenocysteine);
- sea fish and seafood;
- liver and organ meats;
- eggs.
Symptoms and Consequences of Deficiency
A deficiency of selenocysteine can lead to reduced antioxidant protection and impaired thyroid function.
The most common manifestations of deficiency include:
- Fatigue and muscle weakness.
- Decreased immunity.
- Hypothyroidism and related symptoms.
- Increased susceptibility to infections.
Prolonged deficiency increases the risk of cardiovascular diseases, chronic inflammation, and skin problems.
Possible Risks of Excess and Their Manifestations
An excess of selenocysteine most often occurs with high-dose supplements.
Signs of selenium toxicity include:
- nausea, vomiting, diarrhea;
- liver damage;
- disorders of the immune and endocrine systems.
Chronic overdose leads to selenosis — a condition accompanied by:
- hair loss, brittle nails;
- an unpleasant garlic odor from the mouth;
- coordination disorders and neurological disturbances.
To avoid side effects, it is important not to exceed the allowable norm and to consult a doctor when using selenium supplements.