Selenium Supplement Effects, Usage Guide & Dangers

Selenium supplements can be used to promote detoxification, immune support, cardiovascular health and normal thyroid activity.

Selenium is an essential trace mineral with potent antioxidant effects in the human body. It is required to make glutathione and other natural antioxidant enzymes that protect against oxidative damage.

Common food sources of this element include Brazil Nuts, seafood, eggs, meats and dairy. It is found in the human diet as selenomethionine, selenoneine, and gamma-glutamyl-Se-selenomethyl-selenocysteine.

If you have low levels of selenium in the body, it can negatively impact health status and susceptibility to certain disease conditions. In children, a deficiency can result in Keshan disease which is a serious and potentially fatal hearth problem.

Selenium supplements typically provide 200 mcg serving sizes of this micromineral. Use of this supplement at low dosages is rated Likely Safe by the NMCD, but taking more than 400 mcg per day can result in health problems.

Selenium

Essential Mineral

Anti-Oxidant

Immunity

Thyroid Function

How It Works:

• Cofactor for antioxidant enzymes
• Supports thyroid function & metabolism
• Promotes immune function & fertility

Dosage:

Up to 400 mcg per day

Safety:

Rated Likely Safe at Appropriate Dosages

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Selenium Supplement Review

Selenium is a trace element that is essential for human health. It cannot be synthesized inside the body de novo and must be obtained from dietary sources or supplementation.

Selenium is needed for ensuring adequate production and balance of thyroid hormones. It is also used to repair DNA, protect against infections and resist oxidative stress.

According to the University of Melbourne, selenium has only recently been found to be “an essential element to human health”. [1] Most of the recent research has examined its purported anti-carcinogenic properties.

Selenium is a fundamental component of more than two dozen selenoproteins. These proteins contain at least one selenocysteine (Sec) molecule, which is an amino acid.

According to research from Harvard Medical School and the National Cancer Institute, “Although selenoproteins represent diverse molecular pathways and biological functions… most serve oxidoreductase functions”. [2]

An oxidoreductase is an enzyme that catalyzes the transfer of electrons from reductants to oxidants. They help to stabilize oxidative agents and inhibit their potential for causing cellular damage.

There is ongoing research exploring the effects of selenium and selenoproteins on various forms of cancer, cardiovascular disease, cognitive decline, diabetes, thyroid disease and more.

Currently, there is insufficient evidence to rate the efficacy of this supplement for many of these health conditions. More research is needed to determine whether selenium supplements can reduce risk factors for diseases like atherosclerosis or cancer.

Selenium Supplements for Acne

Selenium is purported to have benefits for skin health by supporting thyroid function. The thyroid plays an important role in regulating metabolism and cell division.

Selenium may also support healthy skin by reducing signs of oxidative stress and inflammation. It has been shown to exhibit antibacterial properties and may have benefits for people with acne.

In one study, 14 patients with Papulopustular Acne were given 200 mcg of selenium per day orally with a topical moisturizing cream for over eight weeks.

There was a slight decrease in lesion counts over the baseline from 8.86+8.12 to 11.93+6.83. However, this result was not statistically significant.

More research is needed to determine whether selenium supplementation works for acne and how it influences skin health.

Selenium Supplement for Cancer

Researchers believe that endogenous selenium may play important roles in cancer prevention through its antioxidant effects and its influence on the endocrine and immune systems.

Selenium has been shown to promote natural cell death (apoptosis) in cancer-affected cells and is involved in repairing DNA. [3]

According to the University of Illinois, “Basic research and clinical studies involving animal models and more recently studies in human strongly support the protective role of selenium against various types of cancer.” [3]

However, the FDA does not agree that there is sufficient evidence available to attribute definitive anti-cancer benefits to this supplement. They state that the current research is contradictory and limited.

Epidemiological studies on selenium have found that chronic deficiency in this mineral may increase the risk of developing cancer. Various mechanisms are believed to contribute to the protective effects of this mineral including:

• Induction of apoptosis (normal cell death) in cancer cells;
• Protective effects of selenoenzymes and selenoproteins;
• Inactivation of nuclear transcription factor;
• Beneficial effects on the immune system;
• Detoxification of antagonistic metals;
• Reduction of oxidative stress;
• Regulation of lipoxygenases;

Selenium is also believed to modulate cell cycle arrest, downregulate androgen receptors and inhibit DNA adduct formations. [3]

Some research from placebo-controlled clinical trials suggests that taking a selenium supplement may reduce the risk of certain cancers. However, the FDA has determined that the evidence is currently insufficient and not conclusive.

Selenium Supplement for Thyroid Disease

The thyroid gland stores more selenium than any other organ in the body. Selenium and the mineral iodine are both required to ensure adequate thyroid hormone production.

The thyroid is an endocrine gland that secretes the hormones triiodothyronine (T3) and thyroxine (T4). These hormones affect the basal metabolic rate as well as protein synthesis, thereby influencing many different physiological functions.

Epidemiological evidence demonstrates an association between thyroid function and serum (blood) selenium concentrations.

There is an inverse relationship between selenium and goiter (enlarged thyroid), thyroid volume and thyroid tissue damage in women. [4]

If you do not have enough selenium in your diet, you may experience low thyroid hormone levels which can result in a wide range of health problems. Some signs of hypothyroidism can include obesity, mental slowness, fatigue, mood problems, as well as brittle hair and skin.

Individuals with a deficiency may benefit from taking a selenium supplement to support thyroid function. However, it is not clear whether getting more than the RDA of 55 mcg of selenium can promote thyroid function in healthy adults.

Controlled, randomized trials in subjects with thyroid disease have yielded inconsistent results. More research in humans is needed to understand if and how selenium works for thyroid dysfunction and disease.

Cognitive Decline and Brain Function

Selenium concentrations in the blood generally decline with age, which may be related to problems with absorption of this mineral in elderly persons.

This may have a negative impact on cognitive abilities. Research shows that marginal selenium deficiencies can worsen declines in brain function related to age. [5]

In several human studies, lower baseline selenium levels were associated with increased risk for cognitive decline in the long run. [6]

However, NHANES data from almost 5000 elderly people in the US did not find an association between blood levels of this mineral with enhanced performance on memory tests. [7]

More human research is needed to determine if taking a supplement or increasing intake of selenium-rich foods can affect Alzheimer’s disease, Parkinson’s disease or cognitive decline.

Supplement Side Effects

If you take a selenium supplement, you should be aware of the risk for potential adverse effects.

The Natural Medicines Comprehensive Database (NMCD) rates this micromineral as Likely Safe when taken over short periods of time at appropriate dosages. However, it is rated Possibly Unsafe if used in excessive dosages or taken for extended durations of time.

The selenium RDA (Recommended Dietary Allowance) is 55 micrograms (mcg) per day for healthy adults at least 14 years of age or older. For pregnant and lactating women, the RDA is 60 mcg/day and 70 mcg/day respectively.

The RDA is determined as the amount of dietary intake required to meet the health needs of 97% of the population. It is not necessarily the optimal amount of this mineral to consume, but reflects the amount that prevents dysfunction.

There has been some contention among medical professionals about whether the US RDA for selenium is adequate. Many researchers and practitioners believe that taking more can be beneficial.

Most dietary supplements will contain 200 mcg of this mineral in a single serving, although some products do come in 50 mcg or 100 mcg dosages. This is 364% of the Daily Value for this nutrient.

The upper limit of tolerability (UL) for selenium is 400 mcg/day for healthy adults. Taking more than this amount increases the risk of negative side effects.

Selenium deficiency is rare in the US and Canada among healthy adults who eat a nutritious diet and among people who do not have digestive conditions that impair mineral absorption.

Deficiency can almost always be avoided without the need to take a selenium supplement. However, there may be cases where using a supplement can promote specific health goals.

According to NMCD, taking too much of this mineral can result in selenium toxicity. Some research suggests that taking 200 mcg of selenium daily over 7.7 years increases the risk for Type II Diabetes.

NMCD states that possible effects of too much selenium include hair loss, nausea, fever, vomiting, abdominal pain, respiratory distress, liver or kidney problems, heart problems and exacerbation of existing iodine deficiency.

It is best to seek medical advice before beginning to use a selenium supplement or increasing your intake of food sources of this mineral.

Selenium may interact with certain health conditions, drugs, herbal supplements, lab tests and foods. Consult with a doctor to help you decide whether this supplement is suitable for you.

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