Selenium Side Effects, Dangers of Overdose & Safety Review

Most people do not experience adverse selenium side effects when using this mineral as a dietary supplement

Selenium (Se) is an important trace mineral known to benefit human health. Natural sources of selenium include soil, certain foods – and very small amounts in the air and water.

In research studies, Selenium demonstrates effects that may support immune system and thyroid function. It is also an antioxidant, helping to avoid and repair damage to cells from free radicals.

Selenium is also helpful for reducing inflammation and is believed to have anti-cancer benefits. [1]

When taken in proper amounts, selenium does not normally cause adverse side effects. However, taking too much selenium, acutely or chronically, can cause various reactions.

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

Top Selenium Products* ❯

View User Ratings* ❯

Too Much Selenium Side Effects

As a nutritional supplement, Selenium is rated Likely Safe when used orally and appropriately by the Natural Medicines Comprehensive Database.

When taking at a safe dosage, it is generally well tolerated and unlikely to cause adverse reactions.

The Tolerable Upper Intake Level for this mineral has been established at 400 mcg/day. This means if you use less than this amount, you can reduce the risk of negative effects occuring.

This supplement is rated Possibly Unsafe if used at high dosages or if taken for long periods of time. Dosages of greater than 400 mcg daily can increase the risk of selenium toxicity developing.

If you consume too much selenium as a dietary supplement or from food sources, you may experience negative effects ranging from mild to severe.

Some of these include halitosis (bad breath), nausea, vomiting, fever and diarrhea.

Other side effects of too much selenium include changes in nails, fatigue, irritability, weight loss and alopecia (hair loss). Toxicity can also cause light-headedness, facial flushing, tremor and muscular tenderness.

There is concern that dosages of this supplement taken for long periods of time (200 mcg per day for an average of 7.7 years) can lead to Type 2 Diabetes.

High dosages of this supplement have been shown to increase hepatic insulin resistance (lowering the sensitivity of cells in the liver to the effects of insulin).

However, beneficial effects from selenium can be achieved at lower dosages. Most side effects can be prevented by using it for short periods of time and not taking it in high doses.

Effects of an Overdose

Selenium overdose can cause liver, kidney and heart complications as well. Lung depression is also possible with chronically high intake.

Note that these effects are very rare; occurring only in cases when selenium levels reach poisonous concentrations.

According to NMCD, there have been 9 accidental deaths attributed to selenium poisoning. Cardiac failure is the most common reason for death from too much selenium.

Research has not yet determined at which selenium becomes lethal to humans, but it is many times greater than the typical dosage we derive from foods.

Tolerable Upper Intake Level

Below is a chart with the Tolerable Upper Intake levels for this mineral based on age. The numbers below are general guidelines and needs may vary from individual to individual.

• Infants up to 6 months: 45 mcg per day
• Infants 7 – 12 months: 60 mcg per day
• Children 1 – 3 years: 40 – 90 mg per day
• Children 4 – 8 years: 100 – 150 mcg per day
• Childen 9 – 13 years: 200 – 280 mcg per day
• Children 14 years and older: 400 mcg per day

Selenium Deficiency Side Effects

The University of Maryland Medical Center states that most people get enough selenium in their diets. Deficiencies are rare, especially in developed countries. Groups most likely to be selenium deficient include:

• Those in areas where selenium is deficient in the soil;
• Those undergoing kidney dialysis;
• Those with HIV/AIDS;

According to the Institute of Medicine, Food and Nutrition Board, “The extensive transport of food typically allows people living in low-selenium areas to obtain sufficient amounts of selenium.”. [2]

Discoloration of the fingernails and skin are common side effects of selenium deficiency. A sudden onset of hair loss may also indicate low selenium levels. Interestingly, too much of this mineral can also cause hair loss – on the head, under the arms and/or on the body.

In the body, selenium is important for the formation of special proteins called selenoproteins, which serve a number of functions.

One of their key roles is in facilitating the production of one of the body’s most important antioxidants: glutathione peroxidase.

Glutathione peroxidase helps us to resist viral infections which may lead to serious health conditions. Chronically low selenium levels are associated with weakened immunity. If you are low in selenium, you may develop colds and flus more easily.

Selenium and Energy Levels

Some people with low selenium levels experience chronic fatigue. Low levels of some other nutrients, like pantothenic acid (vitamin B5) and iron, can also cause this effect.

If you are tired all the time, it may be good to discuss vitamin and mineral deficiencies with a doctor or nutritionist.

Another common side effect of selenium deficiency is brain fog. Some people who are deficient in this trace element have difficulties concentrating or recalling information.

Using a mineral supplement is purported to improve mental function, thereby possibly helping to reduce anxiety, depression, irritability and mental fatigue.

Some studies suggest that selenium deficiency may be associated with recurrent miscarriages. When women are lacking selenium, they may experience changes in menstruation.

In men, lacking adequate selenium can degrade sperm motility (spontaneous movement). This can have a negative effect of fertility and the capacity to reproduce.

Chronically deficient levels may also cause hypothyroidism. When the thyroid gland is not able to produce sufficient amounts of thyroid hormone, symptoms including weight gain, fatigue and depression often result.

What are Selenium Supplements Used For?

According to the Natural Medicines Comprehensive Database (NMCD), selenium has been used and studied for cardiovascular disease, diabetes, cancer, hypothyroidism, osteoporosis and rheumatoid arthritis (RA).

It is also used for benign prostatic hyperplasia (BPH), HIV/AIDS, CFS (chronic fatigue syndrome), avian flu and preventing miscarriage.

According to research, selenium exhibits the following benefits:

• Is necessary for fertility and reproduction in both sexes;
• Reduces the risk of autoimmune thyroid disease;
• Possesses beneficial antiviral effects;
• Decreases the risk of some cancers;
• Plays a key role in metabolism;

Currently, the NMCD rates selenium as Likely Effective for treating selenium deficiency. It is rated as Possibly Effective for autoimmune thyroiditis and a condition of elevated plasma fatty acids called dyslipidemia.

All other uses for selenium require more research to determine efficacy. Available clinical evidence for most selenium uses is mixed and conflicting.

The FDA has not approved the use of selenium as a drug for the treatment or prevention of any medical conditions.

In 2010, the FDA released a statement saying that it would permit the following qualified health claim being made for supplements with this ingredient:

“Selenium may reduce the risk of bladder, colon, prostate, rectal and thyroid cancers. Scientific evidence concerning this claim is inconclusive. Based on its review, FDA does not agree that selenium may reduce the risk of these cancers.”

Selenium Dosage Recommendations

The US RDA (recommended daily allowance) for selenium in healthy adults is 55 micrograms (mcg). In the US, the average daily intake is about 125 mcg. The upper tolerable limit (UL) for selenium is 400 mcg/day. [2]

According to Dr. Josh Axe, “Experts warn that it’s crucial that the public understands that selenium benefits work best when levels are met through eating selenium rich foods. No one should exceed recommendations by supplementing with very high doses without consulting a physician.”.

This mineral may affect people with certain diseases or health conditions differently. Talk to your doctor about using a supplement beforehand if you have an autoimmune disease, hypothyroidism, infertility or skin cancer.

Discontinue use if you have an upcoming surgery within the next two weeks.

Selenium can interact with various medications. Be careful if using a supplement in combination with birth control pills, drugs for lowering cholesterol, corticosteroids, niacin and/or chemotherapy drugs.

Too much or too little selenium can be harmful. Discuss selenium side effects and benefits with your doctor before attempting to increase your levels.

Rate This Article

(4 votes, average: 5.00 out of 5, rated)