Selenium is a trace mineral that is essential to human health. It is an antioxidant, which means that it protects cells against oxidative stress. Selenium, in the form of selenoproteins, carries out various functions important in health and metabolism. In particular, it is crucial for immune and brain function, fertility and for protecting against chronic illnesses such as cardiovascular disease, thyroid disease and cancer.
What is the SEPP1 gene?
SEPP1 encodes the selenoprotein P, which is the main selenoprotein that is found in the blood. Selenoprotein P acts as an antioxidant and transports selenium from the liver to tissues for the synthesis of other selenoproteins, including antioxidant enzymes.
What is the effect of genetic variation at the SEPP1 gene?
Individuals with the alleles at the SEPP1 gene have lower selenium concentration in their blood because there is less selenoprotein P available to transport selenium to tissues and, instead, selenium is excreted by the urinary system. The presence of alleles also affects the expression of other selenoproteins, such as antioxidant enzymes, because there is less selenium transported to the tissues.
What is an antioxidant?
Antioxidants are molecules that neutralise free radicals by giving them an electron. Free radicals are unstable, electrically charged molecules in the cells. They can react with other molecules (like DNA) and damage them, as well as forming chain reactions, which form more free radicals.
The damage to cells caused by free radicals, especially the damage to DNA, may play a role in the development of cancer and other health conditions. Antioxidants neutralise free radicals, stop them causing damage to our cells and so may impact the development of cancer.
Why is sufficient vitamin E intake important in relation to selenium?
Selenium is required for the production of the enzyme glutathione peroxidase. The enzyme protects cells from damage by free radicals through inhibition and destruction. In order to perform these roles, vitamin E is required. Without vitamin E, the selenium-dependent enzyme cannot protect the cells from damage as efficiently.
Is selenium more important for some people ?
Adequate selenium is especially important for some groups of individuals, such as individuals with thyroid disease, cancer or a weakened immune system.
It is essential to consume sufficient selenium if you are pregnant. Low selenium in pregnancy is associated with hypertension and preterm birth; whilst higher selenium in pregnant women reduces the risk of hypertension and preterm birth.
Can SEPP1 influence the risk of prostate cancer?
There is some evidence that genetic variations in the SEPP1 gene may influence the risk or progression of prostate cancer.
Selenium is believed to act as a chemopreventative agent in prostate cancer through inhibition of cellular proliferation, apoptosis and antioxidant pathways. This means that it helps inhibit the progression and development of prostate cancer. Individuals with an allele have lower selenium levels and so it is assumed that they have a higher risk of cancer.
Although this is currently a popular area of research and lots of studies do support the link between SEPP1 and prostate cancer, more research needs to be done before this link can be confirmed.
How does selenium improve insulin resistance?
In general, selenium appears to improve insulin resistance and reduce the risk of diabetes via three mechanisms: regulation of concentration of reactive oxygen species, carbohydrate metabolism and lipid metabolism.
However, taking too much selenium (which is rare) actually leads to insulin sensitivity and the development of diabetes. Therefore, if a person is at high risk of developing diabetes, it is important for them to monitor their selenium intake.
Can excess selenium be toxic?
Although selenium is necessary for your health, consuming too much can be toxic. Selenium toxicity is rare but it is important to never exceed the tolerable upper limit of 400mcg per day.
Selenium toxicity from food is rare, although it can result from consuming too many brazil nuts. Toxicity is much more likely to happen from taking supplements rather than from eating selenium-containing foods.
Symptoms of selenium toxicity include nausea, dizziness and tremors. In severe cases, selenium toxicity can lead to serious intestinal, neurological symptoms and kidney failure.
Backed by Science
Our in-house scientists have sorted through thousands of studies and we only use genes that are backed by a significant body of peer-reviewed research. Check out Nell’s Science Standard for more information.