Best Selenium Dosage – How Much to Take Per Day?

The recommended selenium dosage to take will vary depending on your reasons for using this supplement and current health status.

Most dietary supplements provide 200 micrograms (mcg) of this mineral per serving in the form of L-Selenomethionine. This represents 364% of the US Recommended Dietary Allowance for selenium, which is 55 mcg.

Many health professionals believe that higher dosages of this mineral are better for maintaining optimal health. The Food and Drug Administration determines the RDA based on the amount that avoids a nutrient deficiency.

While 55 mcg/day has been shown to prevent selenium deficiency in most healthy adults, there may be certain instances where increasing your dosage of this micromineral has added benefits.

Taking too much selenium can also cause negative impacts on human health. If you consume an excessive dosage for a long period of time, selenium toxicity can occur.

The upper tolerable daily limit (UL) for selenium is 400 mcg/day. This is the recommended maximum dosage to take in the form of supplements or enriched food sources. Continue reading to learn more about how selenium works and dosages that have been used for different purposes.

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 Overview

Selenium (Se) is a trace element with atomic number 34. It is a mineral that is found in small amounts in the soil and in water.

According to the National Institutes of Health (NIH), selenium is essential for human nutrition. This is because it is the primary constituent of dozens of selenoproteins and selenoenzymes.

The National Cancer Institute and Harvard Medical School says that, “selenoproteins represent diverse molecular pathways and biological functions”. [1]

Some of these include roles in reproductive health, DNA synthesis, protecting cells from oxidative damage, helping to resist infection and in normal thyroid hormone metabolism.” [2]

NIH reports that selenium is being studied for its possible effects on cancer, thyroid disease, cognitive decline and cardiovascular disease. [2]

Having low levels of this mineral in the blood can contribute to a number of health conditions and can lead to the following symptoms:

• Muscle weakness
• Fatigue
• Hair loss
• Skin problems
• Immune impairment
• Infertility in males and females
• Poor sperm quality and motility
• Brain fog
• Increased risk of Keshan disease
• Impaired heart function
• Hypothyroidism
• Goiter

While the majority of the population is not at risk for selenium deficiency, certain factors can cause you to require more of this mineral in your diet.

People with digestive conditions like Chron’s disease may need to increase their dosage due to poor absorption of this mineral from the gut.

How Much Selenium Should I Take?

Selenium is an essential nutrient, which means that the body cannot produce it on its own (endogenously). It must be obtained from the diet in the form of food sources or from dietary supplementation.

The recommended dietary allowance (RDA) for Selenium in the United States is as follows:

These are the amounts proposed by the Food and Drug Administration (FDA) as being sufficient to meet the needs of 97% of the population.

If you do not obtain at least this amount from the diet, you may be at risk of deficiency. However, certain health benefits may be attributed to increasing your consumption of this mineral in limited cases.

The Natural Medicines Comprehensive Database (NMCD) rates selenium supplementation as Likely Effective or Possibly Effective for the following conditions:

• Selenium deficiency;
• Autoimmune thyroiditis;
• Dyslipidemia;
• Sepsis;

Researchers are also examining the effects of supplementing with this mineral for other conditions and diseases as well.

It has been studied in asthma, diabetes, infertility, hypothyroidism, HIV/AIDS, burns and cataracts, but has not been approved by the FDA as a drug for the prevention or treatment of any of these conditions.

Researchers are also investigating the effects of higher dosages of this mineral for impeding the development and/or progression of cancer. To date, there have been human studies analyzing the risk for breast, lung, prostate, skin, bladder, colorectal, esophageal, gastric, liver and ovarian cancer.

More research is needed to determine whether selenium can improve risk factors for cancer in humans. Results have been mixed with some studies showing benefits and other studies showing no significant changes in risk profile.

Speak with a doctor about increasing selenium intake before beginning to supplement with this mineral. Getting too much in your diet or taking high dosages of supplements can also cause side effects.

Selenium Dosage for Hypothyroidism

Selenium is important for the metabolism of thyroid hormones in the body. NMCD states that having low levels can inhibit the thyroid gland’s capacity to convert T4 (thyroxine) into T3 (triiodothyronine).

T4 is the inactive precursor to T3, which is the active form of thyroid hormone. This hormone is the master regulator of metabolic function in the body and is involved in many different physiological processes.

One study involving elderly patients found that selenium supplementation can improve T4-to-T3 conversion rates. [3] However, another study reported no significant changes. [4]

There may be a difference in effects depending on whether an individual is deficient in this mineral or has normal thyroid hormone levels. Supplementation may help if you do not get enough through your diet, but may not have benefits for people with adequate levels.

One study involving 2,143 euthyroid (normal thyroid function) pregnant women showed that a 200 mcg daily selenium dosage reduced the chances of developing postpartum thyroid dysfunction by 41%. This same study also reported a 42% decrease in the probability for permanent hypothyroidism. [5]

According to NMCD, multiple studies show that taking 200 mcg/day selenium with levothyroxine significantly reduces thyroid peroxidase antibodies between 6% and 30%.

In these and other studies, selenium is also reported to improve mood, subjective well-being and other quality of life measures. [6] Other research suggests that taking dosages less than 200 mcg daily may not be as effective. [7]

Excessive selenium dosage can exacerbate symptoms associated with iodine deficiency. Those who are deficient in either of these minerals should not use a selenium supplement without also using an iodine supplement.

NMCD states that, currently, there is “no reliable evidence about the effect of selenium on thyroid function or thyroid morphology”. More research is required to determine whether this mineral is effective for improving or preventing thyroid disease or dysfunction.

Selenium Dosage for Male Infertility

NMCD states that people use selenium for both male and female infertility. Research shows that if you do not get enough of this mineral in the diet, it may be harder for women to conceive and for male sperm to fertilize the egg.

According to research from Poland, “…selenium supplementation in subfertile men with low selenium status can improve sperm motility and the chance of successful conception. However, not all patients responded; 56% showed a positive response to treatment.” [8]

Clinical research shows no direct benefits in this area when given to people with adequate dietary intake.

NMCD states that taking between 100 mcg and 200 mcg of selenium, alone or in combination with vitamins A, C and E, “does not improve the density, the size and shape, or the movement of sperm compared to placebo in infertile men”.

Large-scale, randomized human trials are needed to determine the effects of selenium supplementation on male infertility as well as optimal dosage protocols. Getting too much of this mineral can impair sperm motility.

Selenium Overdose and Possible Side Effects

Selenium is considered generally safe when used orally and appropriately. If the UL dosage of 400 mcg/day is not exceeded, there are few side effects associated with supplementation.

Most negative effects are linked to taking too much of this trace mineral in the form of a dietary supplement. Overdoses can be dangerous, especially if taken in high amounts for long periods of time.

Some of the adverse effects linked to selenium toxicity include nausea, vomiting, abdominal pain, weight loss and hair loss. Others include fatigue, irritability, tremor and facial flushing.

NMCD states that in rare cases, acute selenium toxicity can be fatal. There is no well-defined dosage amount at which selenium becomes toxic to humans.

Seek medical advice about the best selenium dose for your health needs. Let your doctor know about all medications and herbals supplements you may use as well as details about your health history.

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