In 1969, the Apollo mission brought back to Earth samples of moon dust. Contained in those samples was selenium. Maybe then, it is no coincidence that the word selenium has its roots in the Greek word, selene, which means “moon.” However, it wasn’t until the early 80’s that the scientific community began to study selenium and its effects on the body. Scientists, within the last decade, are beginning to understand just how vital selenium is to immune response and thyroid functioning. 

What is selenium?

Selenium is a mineral found in soil, water, and some foods. It is required in trace amounts for normal health, and is an essential element in several metabolic pathways.

Why is selenium necessary?

Selenium has antioxidant properties that help the body prevent cellular damage from free radicals, and one of its most valuable roles is as a cofactor of an important antioxidant enzyme in the body called glutathione peroxidase. Selenium also helps support a strong immune system, regulates thyroid function, and may help reduce the risk of prostate and secondary cancers. It also plays a role in the prevention of cataracts and heart disease.

How do our bodies get selenium? 

Selenium is not a naturally occurring substance within the body but a trace mineral found in our foods and soil. And how much we get from our food is dependent on where the food grew. The amount of selenium in soils around the world varies.

How do our bodies utilize the dietary selenium? 

To truly understand the importance of selenium, it is necessary to understand how selenium is utilized from our dietary intakes. It’s synthesized into seleno-enzymes (or selenoproteins). When the body synthesizes selenium, it is converted into one of three types of selenoproteins.

o GPx (glutathione peroxidases) are anti-oxidants 

o TRx (thioredoxin reductases) are active in cell structure and growth.

o DIs (Iodothyronine deiodinases) are responsible for metabolic functions and the conversion of T4 to T3.

Each of these selenoproteins types has a role in thyroid function. In fact, there are 11 selenoproteins involved with the thyroid and thyroid hormone production. Therefore, it comes as no surprise that the selenium content of the thyroid is higher than that of any other body part. During times of selenium deficiency, the body will use any available selenium for the thyroid. This helps to explain the common symptoms of decreased cognitive functions in those who are selenium deficient. Even the brain and neurotransmitters “take a back seat” to the functioning of the thyroid in regards to selenium status within the body.

What does selenium do for the thyroid? 

As stated earlier, selenoproteins in the DIs family convert the storage hormone T4 into the active T3 hormone. It is well documented that only when a severe selenium deficiency is coupled with severe iodine deficiency leads to neurological cretinism. Iodine deficiency also causes goiter but a selenium deficiency results in a “weighty” or heavy thyroid as evidenced by ultrasound results. 

When there is an iodine deficiency and attempts to supplement with selenium occur, the selenium will magnify the iodine deficiency causing it to become worse. The reverse is also true. If there is a selenium deficiency and attempts are made to supplement with iodine, the iodine will exacerbate the selenium deficiency causing it to worsen as well. In fact, anytime one is high and the other is low, symptoms will occur and often times get worse. If there is a deficiency, both must be supplemented or kept low.

Selenium deficiency leads to the exacerbation of Graves, Hypothyroidism, Hashimoto’s and other thyroid disorders. 

The thyroid produces hydrogen peroxide during the production of T4. While some hydrogen peroxide is essential for proper functioning, excessive amounts of it can lead to high T4 production which results in a lower T3 availability. Too much hydrogen peroxide will also cause cell destruction. Selenium as GPx anti-oxidant breaks down excessive hydrogen peroxide and as a TRx prevents cell damage and necrosis of thyrocytes.

What people are most at risk of selenium deficiency?

• Smoke cigarettes

• Drink alcohol

• Take birth control pills

• Have a condition that prevents your body from absorbing enough selenium such as Crohn's disease or ulcerative colitis

What are the signs of a deficiency?

In the United States, selenium deficiency is rare, but in areas where the soil concentration of selenium is low, such as in China, deficiencies are more common. A deficiency in selenium can affect thyroid function and lead to diseases such as: Keshan Disease (enlarged heart and poor heart function in children), Kashin-Beck Disease (results in osteoarthropathy), and Myxedematous Endemic Cretinism (results in mental retardation). Symptoms can include muscle weakness and pain.

How much selenium can I take if I have Hashimoto? Can it reduce antibodies?

Hashimoto is an Auto-Immune Thyroiditis (AIT). The vast majority of experts agree that a good starting therapeutic dose of 200 micrograms (mcg) has positive effects on both the thyroid and the immune system. At this dose, selenium significantly reduces TPO (thyroid peroxidase antibody) and TgAb (Thyroglobulin Antibody) antibodies; up to 55-86% and 35-92% respectively. Attainment of euthyroid status (after long term therapeutic dosing) has also been reported. 

What are good selenium-rich foods? What about supplements? 

Foods rich in selenium include shellfish, Fish, crab, kidney, liver, Sunflower Seeds, Bran (Wheat, Rice, and Oat), Caviar, Shrimp and nuts. It is important to remember that selenium rich food is only so if it is grown or raised in a selenium rich environment. 

Supplements are a great way to ensure proper selenium intake, but there are differences among them. Selenium comes in many forms. Most selenium supplements are selenium yeast, selenomethionine, selenite and selenate. Selenite and selenate are both inorganic forms of selenium. Organic forms of selenium, such as selenium yeast or selenomethionine, are safer and are more readily absorbed. In fact, organic forms of selenium are the only way to raise serum levels of selenium within the body. This is attributed to their bioavailability. 

When using organic forms of selenium, current research shows that doses up to 1600 mcg a day were well tolerated with no signs of toxicity although most experts recommend upper tolerable limits to be 200 mcg a day.

Of the selenium supplements, selenomethionine has the best bioavailability with an absorption rate of 90%. It is organic and yeast free. When compared with other selenium supplements selenomethionine proves to be the most applicable and safest for long-term therapeutic use.

Should I take selenium even if I’m not deficient or don’t have a thyroid issue? 

Selenium supplementation is not restricted to those with selenium deficient status, thyroid disorders, or the immune-compromised. Therapeutic levels help the young and the old alike even those with “normal” selenium levels. Selenium is a necessary component for healthy reproductive status and it aids in normalizing both testosterone and estrogen levels. Selenium aids in the removal of lipids and phospholipids. Excess amounts of these are responsible for high cholesterol levels. A low selenium status is also indicated in those who struggle with depression and mood disorders. And, finally, selenium has been proven a powerful anti-carcinogenic supplement inhibiting cancer cells and reducing the risk of several cancers including prostate, breast, and uterine cancers.

Are there any risks associated with too much selenium?

Selenium toxicity is rare, but high blood levels of selenium can result in selenosis, a condition with side effects including gastrointestinal distress, hair loss, white spots on nails, fatigue, and irritability.

Selenium Possible Interactions

If you are being treated with any of the following medications, you should not use selenium supplements without first talking to your health care provider.

Drugs that affect selenium levels in the body -- These drugs may lower levels of selenium:

• Cisplatin, a chemotherapy drug

• Clozapine (Clozaril)

• Corticosteroids, such as prednisone

• Valproic acid (Depakote)

Anticoagulants and antiplatelet drugs (blood thinners) -- When taken with these drugs, selenium may increase the risk of bleeding:

• Clopidogrel (Plavix)

• Warfarin (Coumadin)

• Heparin

• Aspirin

Barbiturates -- In animal tests, selenium seems to make the sedative effects of these drugs last longer:

• Butabarbital (Butisol)

• Mephobarbital (Mebaral)

• Phenobarbital (Nembutal)

• Secobarbital (Seconal)

Chemotherapy -- Although selenium may help reduce side effects from drugs such as cisplatin, doxorubicin, and belomycin, it may also interfere with their cancer-fighting ability. If you are undergoing chemotherapy, talk to your oncologist before taking selenium or any other supplement.

Cholesterol-lowering medications -- Simvastatin (Zocor) and niacin have been shown to lower LDL ("bad") cholesterol and raise HDL ("good") cholesterol in people with heart disease. Taking antioxidants, including selenium, along with these drugs may make them less effective. 

Birth control pills -- Some researchers theorize that women taking birth control pills may have higher levels of selenium in their blood. If you take birth control pills, ask your doctor before taking extra selenium.

Gold salts -- may lower levels of selenium in the body and cause symptoms of selenium deficiency.

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