Selenium Supplements Review
Choose the Best Selenium
Supplement. Find Out If You Need Selenium and Which Supplement Is Our Top
Pick.
Medically reviewed and
edited by Tod Cooperman, M.D. 
Last Updated
: 03/02/2021 | Initially Posted:
06/28/2019
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Table of Contents
Summary
·
What is selenium? Selenium is an essential mineral
(see What It Is). Only trace amounts of selenium
are needed and deficiency is rare in the U.S. and Canada due to selenium
occurring in foods such as grains and meats, but it is more prevalent in
countries with low levels of selenium in the soil (see "From Food").
·
What are the health benefits of selenium? Selenium is
important for proper immune and thyroid function. There is mixed evidence as to
whether supplementing with selenium can help reduce the risk of cancer: It may
only help those deficient in selenium, while it may be potentially harmful for
others (see What It Does).
·
How much selenium should I take? The daily requirement
for selenium is just 55 micrograms (mcg) for most adults and a bit higher for
women who are pregnant or lactating. Dosage in supplements generally ranges
from 100 to 200 mcg (see What to Consider When Using). The tolerable
upper intake level is 400 mcg daily, above which there is increased risk of
adverse effects such as as hair and nail brittleness
(see Concerns and Cautions).
·
Best selenium supplement? As shown in the comparison graph and Results Table below, the cost to obtain
200 mcg of selenium ranged from 3 cents to $1.39. Among supplements which
passed testing, we identified our Top Pick,
providing a highly absorbable form of selenium at low cost.
What It Is:
Selenium
is a trace mineral that our bodies use to produce glutathione peroxidase — part
of the body's own antioxidant defense system. It works with vitamin E to
protect cell membranes from damage caused by free radicals. Selenium deficiency
may contribute to a weakened immune system, hypothyroidism, and Keshan Disease -- a heart disease of children.
What It Does:
Cancer:
It has been observed that in parts of China where
the soil is depleted of selenium, the incidence of various types of cancer is
much higher than in the rest of the country. This observation has given rise to
a theory that selenium deficiency is a common cause of cancer and selenium
supplements can reduce this risk. In North America, however, selenium
deficiency is uncommon. In people with adequate selenium intake, it is not
clear whether or not additional selenium is helpful. Evidence of a cancer benefit from
supplementing with selenium includes a study that indicated a 50% reduction in
overall cancer deaths when additional selenium was taken — with significant
decreases in cancer of the lung, colon, and prostate (Clark, JAMA 1996). However, results of this
study have been tempered by further analysis indicating that most of the
benefits were seen in study participants with somewhat lower levels of selenium
to begin with (Reid, Canc
Epidem Biomark Prev 2002).
A major study of African-American women in the U.S. found
that those with the highest intakes of selenium from supplements (≥ 20
mcg/day) had approximately a 30% lower risk of ovarian cancer than
those with no supplemental intake of selenium, even after adjusting for other
known risk factors such as age, contraceptive use, and family history (Terry, J Nutr
2017). This association did not exist for intake of selenium from
foods, nor for intake of other antioxidants (carotenoids, vitamin C and vitamin
E) from supplements or food.
Evidence of no cancer benefit or harm from supplementing with
selenium includes a large, multi-year, multi-center human study of selenium
and vitamin E for
preventing prostate cancer which was halted after early
analysis of the data found that selenium and vitamin E supplements, alone or
together, failed to prevent prostate cancer. The analysis also found slightly
more cases of diabetes in men taking only selenium (see Concerns and Cautions for more
information). Part of this study looked at the risk
of developing cataracts and found no benefit with vitamin E
and a small but non-significant benefit with selenium (Christen, JAMA Opthalmol
2014).
Another large study followed men in the U.S. who, after
diagnosis of non-metastatic prostate cancer, took selenium either from selenium
supplements or multivitamins. Compared to those who didn't take selenium, over
a period of about eight years those who supplemented with 1 to 24 mcg, 25 to
139 mcg, and 140 mcg or more of selenium per day were, respectively, 18%, 33%,
and 160% more likely to die from prostate cancer. However, the risk of death
based on all causes, not just prostate cancer, was not higher among the
selenium takers. The researchers concluded that caution is warranted regarding
usage of high-dose selenium (140 mcg or more per day) among men with prostate
cancer (Kenfield, J Natl Canc Inst
2015).
Although some observational studies have suggested that having adequate
selenium levels may reduce the risk of skin cancer and colorectal
cancer, a review of available clinical trials concluded that taking
selenium supplements does not decrease the risk of skin or colorectal cancer,
regardless of selenium status before supplementation (Filippini, Cochrane
Database Syst Rev 2018).
Other supplement ingredients which may have anti-cancer benefits are green tea, lycopene, vitamin E. folate, garlic, soy isoflavones and
other isoflavones, indole-3-carbinol (I3C),
diindolylmethane (DIM), vitamin C and vitamin D. Those
highlighted in blue are the subjects of other reviews or articles on
ConsumerLab.com.
Alzheimer's disease / dementia:
A major, placebo-controlled study among men in the U.S. found that giving
high-dose selenium (200 mcg daily from L-selenomethionine),
vitamin E (400 IU synthetic daily), or both, did not significantly
affect the risk of developing dementia over a 13-year period (Kryscio, JAMA 2017). The study was part of a
larger clinical trial which also evaluated the effects on cancer, diabetes, and
cataracts (see Christen study in "Cancer" section above) and also
found selenium supplementation was associated with a significant increase in
hair loss and dermatitis (see Lippman study in "Concerns and Cautions" section below).
Other uses:
Other potential benefits of selenium have been indicated. Low selenium levels
have been associated with the development of rheumatoid arthritis —
although selenium supplements don't seem to help rheumatoid arthritis once it
has developed (Tarp, Analyst 1995).
There is preliminary evidence that selenium supplements may improve fertility
in males who are selenium deficient. There is weak evidence that
selenium might be helpful for diabetic neuropathy (Kahler, Z Gesamte Inn Med 1993). Greater
bone mineral density has been associated with higher selenium levels
in the blood of postmenopausal women (Hoeg, J Clin Endorinol Metab 2012).
As noted above, selenium deficiency may contribute to a
weakened immune system. A small study in Germany showed that selenium
deficiency was common in people diagnosed with COVID-19, the infection
caused by the SARS-CoV-2 virus, with approximately 39% to 43% having levels
below the 2.5th percentile. Selenium deficiency was also more common in
individuals who died from COVID-19 compared to those individuals with COVID-19
who survived (64% to 70% vs 32% to 39%, respectively). However, it's not
currently known whether selenium deficiency is itself a risk factor for
COVID-19 or a result of having COVID-19 (Moghaddam, Nutrients 2020).
Selenium does not appear to be helpful for preventing heart disease. One fairly
large double-blind study failed to find that use of selenium improved general
sense of well-being (Rayman, Biol
Psychiatry 2006).
Quality Concerns and
Tests Performed:
Like
other supplements, neither the FDA nor any other federal or state agency
routinely tests selenium supplements for quality prior to sale. However,
quality issues can include the following:
·
Labeled Amount — Does the product really contain the
labeled amount of ingredient? Too little may not work. Too much may cause
toxicity, particularly with selenium.
·
Purity — Is the product free of lead, cadmium, and arsenic —
contaminants found in certain types of supplements.
·
Ability to Break Apart for Absorption — Will the tableted
product break apart properly so that it can release its ingredient in the body?
For a tablet to be most useful, it must fully disintegrate prior to leaving the
stomach, delivering its contents for absorption in the gut. Some tablets are
not properly made and can pass through your body completely or partially
intact, depriving you of its ingredients. Remnants of such products are
sometimes found in the stool. This happens, for example, when a tablet is too
tightly compressed (too "hard") or is too thickly coated.
ConsumerLab.com, as part
of its mission to independently evaluate products that affect health, wellness,
and nutrition, purchased commonly available selenium supplements and tested
them to determine whether they 1) possessed the claimed amount of key
ingredient, 2) were able to disintegrate fully to be available for absorption
if they were tablets or caplets and 3) were free from unacceptable levels of
lead, cadmium, and arsenic if their formulas contained whole herbs or more than
250 mg of minerals (see Testing Methods and Passing Score).
What CL Found:
All ten of the selenium supplements selected by CL passed
testing and review, an improvement over CL's last review of this category in
which one product contained only 23.7% of its listed selenium and another
product lacked adequate label information. Two additional selenium supplements
tested through CL's voluntary Quality Certification Program also
passed testing.
Be aware that the amount of selenium in a daily serving of most products in
this review is relatively large -- typically 200 mcg, which is nearly four
times the daily requirement for adults. If you already get a similar amount of
selenium from other supplements and/or your diet, you could be exceeding the
daily Upper Tolerable Intake Level (UL) for selenium, which is 400 mcg for
adults. Although none of the products in this review were specifically marketed
for children, also be aware that, at the suggested serving sizes, most exceed
the UL for selenium for young children, which ranges from 45 mcg to 150 mcg.
See Concerns and Cautions for more
information.
Top Pick:
The
cost to obtain 200 mcg of selenium from the Approved products ranged from as
little as 3 cents (from Spring Valley [Walmart] Selenium
200 mcg) to as much $1.39 (from MegaFood
Selenium), as shown in the chart below.
Although the Spring Valley product is the cheapest, it is made
from yeast and includes wheat, so, to avoid potential allergic reaction to
yeast and sensitivity to gluten, you can spend two cents more to get the same
amount of selenium as selenomethionine (perhaps the
best-absorbed form of selenium) from NOW Selenium 200 mcg,
which is our Top Pick. The NOW product
comes as a "veg capsule," so it is also "vegetarian/vegan"
and is not manufactured with yeast, wheat, soy, milk, egg, shellfish or tree
nut ingredients.
Test Results by Product:
Listed
below are the test results for twelve supplements, listed alphabetically.
ConsumerLab.com selected ten of these products. Two other products (each
indicated with a CL flask) were tested at the request of their manufacturers/distributors
through ConsumerLab.com's voluntary Quality Certification Program and are
included for having passed testing.
Shown for each product are the claimed amount and form of selenium as well as
the serving size and suggested daily servings as recommended on the label.
Products listed as "Approved" met their label claims and ConsumerLab.com's quality criteria (see Passing Score). Certain
special features of products as well as price information and the cost to
obtain 200 mcg of selenium from each product are also listed. The full list of
ingredients is in the last column.
Results of
ConsumerLab.com Testing of SELENIUM SUPPLEMENTS
(Click arrows or swipe left or right to see all columns)
Approval Status
Product Name
(Suggested Serving on Label)
Contained Claimed Amountⓘ of
Selenium
Daily Serving Suggested on Label
Tablets/Caplets Disintegrated Properly
Cost for Suggested Serving
[Price per 200 mcg Selenium]
Price
Notable Features
Full List of Ingredients
(Per Serving)
APPROVED
365® [Whole Foods] Selenium 100 mcg
Dist. by Whole Foods Market
1 tablet:
100 mcg
Seleno-
methionine
✔
Take 1 tablet, one to two times daily with food.
(Medium circular vegan tabletⓘ)
✔
$0.07
[$0.13]
$7.99/120 vegan tablets
Vegan. Contains No Artificial Colors, Flavors Or
Preservatives. No Yeast Formula.
Precaution: Produced In A Facility That Processes Tree Nuts, Milk,
Eggs, Shellfish, Fish, Wheat And Soy.
1 tablet:
Selenium (as seleno-
methionine) 100 mcg.
Other Ingredients: Dicalcium Phosphate, Microcrystalline Cellulose, Stearic
Acid (Vegetable Source), more...
APPROVED
Allergy Research Group® Selenium Solution
Dist. by Allergy Research Group®
1/2 tsp [2.5 ml]:
100 mcg
Sodium selenite
✔
As a dietary supplement, 1/2 teaspoon one to
three times daily, or as directed by a healthcare practitioner.
(Liquid from bottleⓘ)
$0.15
[$0.29]
$13.77/8 fl. oz. [236 ml] bottle (approx. 94 servings)
Hypoallergenic.
1/2 tsp [2.5 ml]:
Selenium (as Sodium Selenite) 100 mcg.
Other Ingredients: Deionized water, sodium hydroxide.
APPROVED
GNC Selenium 200 mcg
Dist. by General Nutrition Corporation
1 caplet:
200 mcg
Selenium yeast
✔
As a dietary supplement, take one caplet daily.
(Medium/large vegetarian capletⓘ)
✔
$0.05
[$0.05]
$9.99/200 vegetarian caplets
No Sugar, No Artificial Colors, No Artificial
Flavors, No Preservatives, Sodium Free, No Corn, No Dairy.
Precaution: Contains: Wheat.
1 caplet:
Calcium 35 mg, Selenium (as Selenium Yeast) 200 mcg.
Other Ingredients: Cellulose, Dicalcium Phosphate.
APPROVED
Life Extension® Super Selenium Complex
Dist. by Quality Supplements and Vitamins, Inc.
1 capsule:
200 mcg
Se-methyl L-Selenocysteine, SelenoPure™ L-seleno-
methionine, sodium selenite
✔
Take one (1) capsule daily with food, or as
recommended by your healthcare practitioner.
(Medium/large vegetarian capsuleⓘ ⓘ)
$0.11
[$0.11]
$10.50/100 vegetarian capsule
Non-GMO.
1 capsule:
Vitamin E (as D-alpha tocopheryl succinate) 20.1 mg,
Selenium (as Se-Methyl L-Selenocysteine, SelenoPure®
L-seleno-
methionine (yeast free), sodium selenite) 200 mcg, more...
APPROVED
Mega Food®Selenium
Mfd. by MegaFood
1 tablet:
50 mcg
Mineral bound S. cerevisiae
✔
Also tested for heavy metalsⓘ.
✔
1 tablet daily.
(Medium circular tabletⓘ)
✔
$0.35
[$1.39]
$20.85/60 tablet
Non GMO Project Verified Seal. NSF Certified
Gluten-Free Seal. Certified Vegan Vegan.org Seal. Soy Free. Dairy Free. Kosher.
1 tablet:
Selenium (mineral bound S. cerevisiae) 50 mcg, Nourishing Food
Blend [S. cerevisiae, Organic Spinach, Organic Ginger Root, Organic
Turmeric Root, Organic Rosemary Leaf, Organic Parsley Leaf, more...
APPROVED
Natural Factors® Selenium 200 mcg
Dist. by Natural Factors
1 tablet:
200 mcg
Yeast
✔
1 tablet daily or as directed by a health care
practitioner.
(Medium circular tabletⓘ)
✔
$0.11
[$0.11]
$6.69/60 tablets
Non-GMO. Contains no artificial colours, preservatives, or sweeteners; no dairy, starch,
sugar, wheat, gluten, soy, corn, egg, fish, shellfish, animal products, salt,
tree nuts, or GMOs. Suitable for vegetarians/ vegans.
1 tablet:
Selenium (yeast) 200 mcg.
Non-Medicinal Ingredients: Dibasic calcium phosphate dihydrate,
microcrystalline cellulose, vegetable grade magnesium stearate (lubricant).
APPROVED
Nature's Way® Selenium 200 mcg
Dist. by Nature's Way Brands, LLC
1 capsule:
200 mcg
L-seleno-
methionine
✔
Take 1 capsule daily, preferably with food.
(Large capsuleⓘ ⓘ)
$0.05
[$0.05]
$4.90/100 capsules
Gluten Free. No sugar, salt, yeast, wheat, corn,
soy, dairy products, artificial colors, flavors or preservatives.
1 capsule:
Selenium (as L-seleno-
methionine) 200 mcg.
Other Ingredients: Cellulose, gelatin (capsule).
APPROVED
Top Pick
NOW® Selenium 200 mcg
Mfd. by Now Foods
1 capsule:
200 mcg
L-seleno-
methionine
✔
Take 1 capsule daily with a meal.
(Large veg capsuleⓘ ⓘ)
$0.05
[$0.05]
$9.56/180 veg capsules
Kosher. Vegetarian/ Vegan. Yeast-Free. Not
manufactured with yeast, wheat, gluten, soy, milk, egg, fish, shellfish or tree
nut ingredients.
1 capsule:
Selenium (from L-Seleno-
methionine) 200 mcg.
Other Ingredients: Rice Flour, Hypromellose (cellulose capsule) and Stearic
Acid (vegetable source).
APPROVED
Puritan's Pride® High Potency Selenium 200 mcg
Mfd. by Puritan's Pride, Inc.
1 tablet:
200 mcg
Selenium yeast
✔
For adults, take one (1) tablet daily,
preferably with a meal.
(Medium circular tabletⓘ)
✔
$0.08
[$0.08]
$15.98ⓘ/2 bottles of 100
tablets (200 tablets total)
Vegetarian. No Artificial Color, Flavor or
Sweetener, No Preservatives, No Sugar, No Starch, No Milk, No Lactose, No Soy,
No Fish, Sodium Free.
Precaution: Contains wheat ingredients.
1 tablet:
Selenium (as Selenium Yeast) 200 mcg.
Other Ingredients: Brewer's Yeast, Vegetable Cellulose, Vegetable Stearic Acid,
Silica, Vegetable Magnesium Stearate.
APPROVED
Spring Valley™ [Walmart] Selenium 200 mcg
Dist. by Wal-Mart Stores, Inc.
1 tablet:
200 mcg
Selenium yeast
✔
Adults, take one tablet daily, preferably with a
meal.
(Medium circular tabletⓘ)
✔
$0.03
[$0.03]
Lowest cost for Approved selenium
$5.32/2 bottles of 100 tablets (200 tablets total)
No Milk or Milk Derivatives, Lactose, Sugar,
Preservatives, Soy, Artificial Color, Artificial Flavor, Sodium (less than 5 mg
per serving).
Precaution: Contains Wheat.
1 tablet:
Selenium (as Selenium Yeast) 200 mcg.
Other Ingredients: Brewer's Yeast, Cellulose (Plant Origin), Croscarmellose,
Vegetable Stearic Acid, Silica, Vegetable Magnesium Stearate.
APPROVED
Swanson Ultra® SelenoExcell®
Dist. by Swanson Health Products
1 capsule:
200 mcg
SelenoExcell® organically bound high-selenium yeast
✔
As a dietary supplement, take one capsule per
day with water.
(Medium/large capsuleⓘ ⓘ)
$0.05
[$0.05]
$2.84/60 capsules
None.
1 capsule:
Selenium (from SelenoExcell® organically bound
high-selenium yeast) 200 mcg.
Other Ingredients: Rice flour, gelatin, magnesium stearate.
APPROVED
The Vitamin Shoppe® Selenium
Dist. by Vitamin Shoppe, Inc.
1 tablet:
200 mcg
L-seleno-
methionine
✔
Take one (1) tablet daily, preferably with a
meal.
(Medium circular tabletⓘ)
✔
$0.10
[$0.10]
$9.99/100 tablets
Gluten free. Dairy free. Soy free. Nut free.
Does not contain: Gluten, Sugar, Salt, Preservatives, Artificial Colors or
Flavors.
1 tablet:
Calcium (as dicalcium phosphate) 50 mg, Phosphorus (as dicalcium phosphate) 39
mg, Selenium (as L-seleno-
methionine) 200 mcg, more...
Unless otherwise noted, information about the
products listed above is based on the samples purchased by ConsumerLab.com (CL)
for this Product Review. Manufacturers may change ingredients and label
information at any time, so be sure to check labels carefully when evaluating
the products you use or buy. If a product's ingredients differ from what is
listed above, it may not necessarily be of the same quality as what was tested.
The information contained in this report is based
on the compilation and review of information from product labeling and analytic
testing. CL applies what it believes to be the most appropriate testing methods
and standards. The information in this report does not reflect the opinion or
recommendation of CL, its officers or employees. CL cannot assure the accuracy
of information.
Copyright ConsumerLab.com, LLC, 2021 All
rights reserved. Not to be reproduced, excerpted, or cited in any fashion
without the express written permission of ConsumerLab.com LLC
ConsumerTips™:
What to
Consider When Buying:
From food:
Most individuals in the U.S. and Canada are believed to consume more than
enough selenium from their diets. Foods containing significant and reliable
amounts of selenium include animal products like meat, seafood, and dairy
foods, as well as whole grains and vegetables grown in selenium-rich soils.
Below are amounts of selenium in selected foods tested by the USDA (click here for full
list):
·
Brazil nuts, dried: 543.5 mcg / oz (6-8 nuts)
·
Rockfish, cooked: 113.5 mcg / 1 fillet
·
Tuna, yellowfin, cooked: 92 mcg / 3 oz
·
Halibut, cooked: 88.1 mcg / ˝ fillet
·
Salmon, red sockeye with skin 82 mcg / 1 filet
·
Chicken liver, cooked 75 mcg / 3 oz.
·
Wheat flour, whole grain: 74.2 mcg / 1 cup
·
Potatoes, mashed, ready-to-eat 61.6 mcg / 1 cup
·
Couscous, cooked: 43.2 mcg / 1 cup
·
Wheat flour, white, all-purpose, enriched 43 mcg /1 cup
·
Egg, hardboiled, chopped 41.9 mcg/ 1 cup
·
Rice, white, long-grained, enriched, dry: 36.8 mcg / 1 cup
·
Cheese, mozzarella, low moisture, part-skim 36.4 mcg / 1 cup
·
Turkey, light or dark meat, cooked 36 mcg /3 oz.
·
Mushrooms, shiitake, cooked, chopped 36 mcg / 1 cup
·
Spinach, frozen, chopped or leaf 9.4 mcg / 1 cup
The selenium content of
food varies depending on the selenium content of the soil in which it was
grown. Studies suggest that many people in certain developed countries,
including New Zealand, Belgium, and Scandinavia, do not get enough selenium in
their diets.
As a supplement:
Selenium compounds are generally very efficiently absorbed by humans. For
example, absorption of the selenite form of selenium is greater than 80 percent
whereas that of selenium as selenomethionine
(selenium bound to methionine, an essential amino acid) or as selenate may be
greater than 90 percent (FAO 2002). Selenium from yeast (which contains
selenomethionine) is also believed to be slightly
better absorbed than selenite. Selenized yeast is
brewer's yeast that has been grown in selenium rich broth and then used as a
selenium supplement.
Se-methyl-L-selenocysteine is a naturally occurring form of selenium which,
like selenomethionine, also occurs in yeast and it
represents about 80% of the total selenium in vegetables such as broccoli,
radish, Brussels sprouts, cabbage, garlic, onion, and leek. Based on animal
studies, it is also readily absorbed and bioavailable, and its toxicity appears
to be comparable to, or possibly higher than, that of other selenium compounds
(European Food Safety Authority,
2009). However, as it has not been studied as a supplement in humans
as much as other forms of selenium, it may be advisable to limit amounts taken
as a supplement until more is known.
What to Consider When Using:
The Recommended Daily Allowance (RDA) for selenium is 20 mcg for children 1 to
3, 30 mcg for those 4 to 8, and 40 mcg for those 9 to 13. For individuals 14
and older the RDA is 55 mcg. However, the RDA for pregnant woman is 60 mcg and
for nursing women it is 70 mcg per day.
Since it is the deficiency of selenium that is potentially associated with
cancer risk, getting the RDA should be sufficient to have benefit. However, a
higher dose (200 mcg of selenium supplied as a 0.5 gram high-selenium brewer's
yeast tablet daily) has also been used in studies.
For patients infected with human immunodeficiency virus (HIV), 250 mcg of L-selenomethionine daily has been used for 12 months,
although it is not clear that this provides any benefit.
Bear in mind that certain digestive conditions, such as Crohn's disease,
short-bowel syndrome and ulcerative colitis, might impair selenium absorption.
Medications that reduce stomach acid might also reduce absorption of selenium.
At very high doses selenium can cause hair loss and tissue damage (see Concerns
and Cautions below).
Concerns and Cautions:
Maximum
safe doses of selenium for individuals with severe liver or kidney disease have
not been established. At doses above the tolerable upper intake level (UL) of
400 mcg per day for adults and children 14 and older, hair and nail
brittleness and loss occur. The UL is lower for younger individuals. The
tolerable upper intake level (UL) for infants up to age 6 months is 45 mcg per
day; for infants 7 to 12 months, 60 mcg per day; for children 1 to 3 years, 90
mcg per day; for children 4 to 8 years, 150 mcg per day; for children 9 to 13 years,
280 mcg per day. Note that these dosages apply to combined dietary and
supplemental intake of selenium; when deciding how much selenium it's safe to
take, keep in mind that most adults already receive about 100 mcg of selenium
in the daily diet.
Other signs of selenium toxicity, typically beginning at about 900 mcg daily,
are depression, nervousness, emotional instability, nausea, and
vomiting.
While additional selenium intake may benefit people with
low selenium levels (serum selenium below 122 mcg/L), people with
adequate-to-high status (122 mcg/L or greater) might be affected adversely and
should not take selenium supplements (Rayman, Lancet 2012).
For example, a multi-year study in the U.S. found that, among people with
higher selenium levels, those given 200 mcg of selenium per day were 2.7 times
as likely to develop type-2 diabetes as those who received
placebo. There was no significant increase in diabetes among those who started
with lower levels of selenium (Stranges, Ann Intern
Med 2007). Another study
that followed 21,334 men and women in Italy who did not have
diabetes at the start of the study found that those who reported the highest
dietary intakes of selenium (median of 88 mcg/day for men and 77 mcg/day for
women, which is above the 55 mcg RDA for selenium but still below the UL) at
baseline had a 64% greater risk of being hospitalized for type 2 diabetes over
the next eight years of follow-up than those with lower intakes (44 to 67
mcg/per day for men and 39 to 62 mcg/day for women). Increased selenium intake
tended to arise from higher intakes of milk, meat, and fish. The increased risk
associated with the highest intakes of selenium was independent of BMI (body
mass index), another risk factor for type 2 diabetes (Vinceti, Nutr Metab Cardiovasc Dis 2021).
A study in Denmark among adults with low selenium levels (90
mcg/L or lower) who took 100 mcg, 200 mcg, or 300 mcg of selenium daily for 5
years and were followed for an additional ten years found that those who had
taken the 300 mcg dose had an 11% greater risk of death from
all causes compared to placebo and the lower doses had no effect (Rayman, Free Radic Biol Med
2018). The researchers concluded that total selenium intake
over 300 mcg per day as well as high-dose selenium supplements should be
avoided; however, they also noted that even a daily supplemental dose of 200
mcg could result in toxicity in populations where selenium levels are typically
already high, such as in the U.S., where the average blood level of selenium is
137 mcg/L.
A large, multi-year study of selenium and vitamin E for
preventing prostate cancer found that supplementing with high-dose selenium (200
mcg daily from L-selenomethionine) increased the risk
of high-grade prostate cancer by 91% among men with already
high levels of selenium and had no effect on men low in selenium.
Interestingly, the study also found that vitamin E increased
the risks of both low-grade and high-grade prostate cancer by 46% and 111%,
respectively, when given to men low in selenium but did not have this effect in
men with already high levels of selenium. This evidence suggests that having
sufficient selenium levels is advantageous, but excess selenium poses risks.
The researchers cautioned that men 55 years and older should avoid
supplementation with either vitamin E or selenium at doses that exceed
recommended daily intakes (Kristal, JNCI 2014).
Another report based on this study found that use of the selenium was
associated with a significant increase in hair loss and dermatitis (Lippman, JAMA 2009). A study of men who
already had non-metastatic prostate cancer found a higher risk of subsequent
death from prostate cancer among those taking selenium and cautioned that men
with prostate cancer should not take more than 140 mcg per day of selenium from
supplements (Kenfield, J Natl Canc Inst
2015).
Information on this site
is provided for informational purposes only. It is not an endorsement of any
product nor is it meant to substitute for the advice provided by physicians or
other healthcare professionals. The information contained herein should not be
used for diagnosing or treating a health problem or disease. Consumers should
inform their healthcare providers of the dietary supplements they take.
Latest Clinical Research Updates for Selenium Supplements
3/03/2021
High intake of selenium
from the diet or supplements has been associated with increased risk of type 2
diabetes. Get the details in the Concerns and Cautions section of our
Selenium Supplements Review.
7/18/2020
Selenium-deficient people
were more likely to die from COVID-19 than those who were not deficient
according to a recent study. For details, see the What It Does section
of the Selenium Supplements Review. Also see our Top Pick for selenium.
2/21/2018
Taking too much selenium
was found to increase the risk of death in a newly published study. How much is
too much? Get the details in the Concerns and Cautions section
of the Selenium Supplements Review.
Vitamin E/Selenium & Alzheimer's
3/29/2017
A long-term study among
men in the U.S. found that giving high doses of vitamin E and/or selenium did
not significantly affect their risk of developing dementia. The study was part of
a larger study which found that these supplements increased the risk of
prostate cancer, type 2 diabetes, hair loss, and dermatitis. For details, see
the "Alzheimer's
disease/dementia" section of the Selenium Supplements Review >>
2/18/2017
A recent study found that
women with the highest intakes of selenium from supplements had a much lower
risk of ovarian cancer than those not getting selenium from supplements. Get
the details in the "What It Does" section of
the Selenium Supplements Review (which includes our tests of products) >>
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