Ever had a lot of nuts or seafood lately? A meal or snack heavy in meats, nuts, or dairy has a lot of selenium in it, an essential nutrient for human health. We might even have had some in our drinking water recently, depending on where we live. But what exactly is selenium used for? Its primary functions may include helping prevent cardiovascular diseases, certain cancers, and even thyroid disorders, though more research is needed to thoroughly confirm these benefits of selenium.
What is Selenium?
Selenium is a naturally-occurring chemical component essential to human nutrition. It is composed of several dozen smaller selenoproteins that help with reproduction and DNA synthesis and protects against oxidative stress and infection. Most of the body’s selenium supply is stored in skeletal muscle, where it exists in the form of selenomethionine and is incorporated with the amino acid methionine within body proteins (x).
Despite its importance, selenium is not widely available all over the world. The more selenium there is in the soil, the more selenium growing food will carry. In some parts of the world, selenium deficiency has been lessened through supplementation programs (x).
Benefits of Selenium
Managing and Preventing Cardiovascular Disease
Because selenoproteins help protect against oxidative stress and reduce inflammation, selenium might prove useful in managing and preventing cardiovascular disease. In theory, oxidative stress can kickstart several human diseases, so managing that stress can be key in preventing them.
A 2006 study from the Department of Epidemiology at John Hopkins University tried to find a connection between selenium consumption and coronary heart disease through randomized trials. In observational studies, a 50% increase in selenium concentrations might have been associated with a 24% reduction in the risk of coronary heart disease (x).
On the other hand, a 2011 study from the University of Surrey in England says that high selenium consumption has been linked to high blood cholesterol levels. Participants received 100, 200, or 300 mcg of selenium-based yeast or a placebo for six months. Total plasma cholesterol levels and non-high-density lipoprotein (HDL) plasma cholesterol levels were reduced compared to the placebo group. However, the 300 mcg dose increased HDL levels (x).
Evidence linking selenium consumption to low risk of cardiovascular disease has been mixed. This may be because several clinical trials have been performed on relatively healthy male adults. A 2013 study from the Division of Health Sciences at the University of Warwick tried to determine whether selenium-only supplementation would help prevent cardiovascular disease. No significant reductions or changes were observed as a result (x).
Similarly, a 2010 study from the Health Sciences Research Institute looked at a wide sample of British adults to find a connection between selenium and cardiovascular health. Higher plasma selenium levels were associated with both increased non-HDL-cholesterol and total levels among this population. The study showed that higher serum levels might interfere with lipid metabolism and might actually have adverse effects on cardiovascular health (x).
Thyroid Disorder Management
Selenium benefits include possibly helping to manage thyroid disorders, mainly because selenium helps produce and metabolize the thyroid hormone. Selenium deficiency might affect an individual’s selenoprotein activity, which might also contribute to autoimmune thyroid diseases (x).
Four randomized trials from the Department of Nuclear Medicine in Vienna looked at whether selenium supplementation could be an adjunct (additional) treatment to levothyroxine in Hashimoto thyroid patients. Three of these four trials gently suggested a reduction of circulating autoantibodies but did not provide information about whether selenium could improve symptoms for an allowed reduced dosage of levothyroxine (x).
A 2011 study from the Department of Endocrinology and Metabolism in Italy looked at whether it could improve symptoms for patients with mild Graves’ orbitopathy. The 6-month treatment of either selenium or placebo was associated with an improved quality of life, as well as a slowed progression of the disease (x).
Some studies show that women with higher levels face fewer thyroid problems, but the same has not been proven for men (x).
Cognitive Decline Protection
Other studies have been conducted into whether selenium consumption can help protect against cognitive decline in the elderly. Selenium levels naturally decrease with age, and age-related brain decline might be because of some selenium deficiencies. Some studies have shown that excessive oxidative stress can lead to some cognitive decline (x).
However, results as to whether selenium actually improves cognitive function have been mixed. A 1999 study from the Regenstrief Institute for Health Care in Indianapolis tried to find a link between selenium consumption and memory improvement in a group of elderly subjects, and no substantial link was found between the two (x).
Similarly, studies have tried to find a link between selenium supplements and cognitive impairment. It’s been proven that antioxidant properties of some vitamins may help prevent cognitive decline, so it might be able to do the same.
A 2011 study looked at the long-term effects of antioxidant nutrient supplementation on cognitive performance after the end of a vitamin supplement trial that took place six years prior. The subjects that received active antioxidant supplementation had better episodic memory, but verbal memory was improved only in the subjects who didn’t smoke and had low Vitamin C concentration at the beginning of the study (x).
Selenium supplements have not been prescribed to patients who are at risk for cognitive diseases like Alzheimer’s since more research is needed to test its effectiveness against them (x).
Protection Against Cancer
Because of its antioxidative properties, it might play a role in helping to manage or protect against certain kinds of cancers.
A 2011 Germany study tested selenium exposure against cancer risk and found a reduced cancer risk with greater selenium exposure, though that reduction was more prominent in men than women. However, the study had limitations with certain kinds of cancer and some results were inconsistent. More studies are needed to confirm whether it has any kind of effect on cancer management or prevention (x).
In 2003, the FDA allowed a health claim on all products containing it to say that while there was some scientific evidence that suggested it may help reduce the risk of certain cancers, that more evidence was needed to further confirm that notion (x).
In 1998, selenium was tested as a chemopreventive agent at the Division of Nutritional Sciences at the University of Cornell, taking note that various animal models have suggested that it prevents certain cancers. The model found that people who have adequate intake might still benefit from selenium supplements to reduce tumor incidence (x). Certain meta-analyses have pointed toward high selenium status having a 31% lower risk of cancer at any site (x).
Side Effects
While selenium is a naturally-occurring chemical and is important for human function, it can be taken in excess. Some signs of too much consumption are a metallic taste in the mouth, along with a slight garlic odor to the breath. Some hair and fingernails might be lost or turn brittle. Nausea, skin rashes, diarrhea, fatigue, and nervous system lesions might also occur (x).
If Brazil nuts are a favorite snack, patients must exercise caution, as consuming too many presents a risk of developing selenium toxicity. Symptoms of acute selenium toxicity may include acute respiratory syndrome, hair loss, tremors, lightheadedness, cardiac failure, and facial flushing. Rare cases of this disease may cause death (x).
Warnings and Precautions
Selenium can be taken with some medications, but patients wishing to supplement selenium with other medications should speak to their doctor first.
Selenium is required for health, so the only way it’s dangerous is if a consumer overindulges.
How to Take Selenium
The best way to get selenium is through the food we eat. Foods high in it will also usually be high in protein, including nuts, some fish, eggs, and meats, as well as some grain and dairy products, like cereal and yogurt. We can get a small amount of it from water, but that might not be available in all areas and is not significant enough to make much of a difference.
How much selenium there is in certain foods also depends on the pH of the soil the food is grown in. Animal products have a larger concentration because the animals can maintain it through homeostasis, so they will normally contain the same levels of it. Foods like Brazil nuts, halibut, shrimp, beef, and turkey have the highest concentration of it according to the U.S. Department of Health and Human Services (x).
Otherwise, selenium supplements are available as a multivitamin/multimineral and a stand-alone supplement.
The recommended daily intake for adults is 55 mcg, while pregnant women should consume 60 mcg. Lactating women should consume 70 mcg per day. The upper limit of selenium for an adult to consume is roughly 400 mcg. Most experts recommend getting it from your diet rather than supplements (x). Different age groups will require different dosages, so be sure to consult a healthcare provider about which dosage is best for you.
Where to Buy Selenium
You can purchase selenium supplements at BulkSupplements.com. The company is an industry-leading manufacturer and distributor for pure dietary supplements. BulkSupplements.com is not just a consumer brand. It also supplies pure ingredients to other brands that distribute food and other supplement products. All products at BulkSupplements.com are manufactured and tested according to current and proper manufacturing practices.
Are you interested in testing selenium’s antioxidative abilities against cancer and heart disease?
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Bottom Line
Selenium is much more common a nutrient than it may seem, usually being found in meats, nuts, and some dairy products. Consumers must be careful not to eat too much because too much selenium can be toxic. While the results of some studies surrounding selenium’s antioxidative properties have been positive, more research is needed to confirm selenium’s effects on various diseases.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.