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Selenium is a trace mineral, which means the body only requires it in very small amounts. It is naturally present in many foods and is also available as a dietary supplement.

The majority of selenium from our diet gets stored in muscle tissue, though the thyroid is the organ with the highest concentration.

Selenium is an important component of enzymes and proteins — known as selenoproteins — that play a key role in reproduction, thyroid hormone metabolism, and DNA synthesis.

Selenoproteins also act as powerful antioxidants that help protect against damaging particles in the body called free radicals.

Free radicals are unstable atoms produced naturally in the body as a byproduct of normal functions within the body. They cause damage to cell membranes and DNA. Over time, this can lead to inflammation, premature skin aging, and a host of age-associated diseases.

Biological aging is a complex process that involves molecular damage, metabolic imbalance, immune system changes, and increased susceptibility to environmental stressors and disease.

According to a review from 2018, selenium can fight aging and prevent age-related health issues, such as tumors, cardiovascular disease, and neuropsychiatric disorders. Some researchers also believe that selenium can reduce chronic inflammation, which is closely related to aging.

According to some research, selenoproteins are primarily responsible for many of the health benefits of selenium.

For example, one 2021 review found that selenoproteins play a key role in controlling and removing misfolded proteins, which accumulate as we age. Specialists note that the accumulation of misfolded proteins is a common characteristic of aging and age-related diseases, including type 2 diabetes and Alzheimer’s disease.

Experts also believe that selenium protects the skin against ultraviolet (UV) oxidative stress by stimulating the selenium-dependent antioxidant enzymes glutathione peroxidase (GPx) and thioredoxin reductase (TDR). TDR is located in the plasma membrane of epidermal keratinocytes. This may potentially combat aging skin caused by UV exposure.

Moreover, a newer study from 2020 found that increased dietary intakes of selenium are associated with longer telomeres. This study found that every 20 microgram increase in dietary selenium was associated with a 0.42% longer telomere length in participants over the age of 45.

Telomeres are “protective caps” located on the ends of our chromosomes that affect how quickly cells age. Some experts consider telomere length as an informative biomarker of aging.

Researchers also believe that higher levels of selenium are associated with longevity. The all-cause mortality of older adults with low selenium levels is significantly higher than that of the elderly with a high level of selenium.

For example, centenarians often appear to have higher systemic levels of selenium and iron while having lower levels of copper than other older people.

However, it is important to note that results remain conflicting and more research on the topic is needed. Some studies — such as the one referred to above — suggest that low levels of selenium may actually promote longevity.

Selenium may also play an important role in the protection against certain age-related diseases.

Heart disease

One meta-analysis found that people with lower selenium levels are at a higher risk of coronary heart disease. In contrast, a review of trials that used only selenium supplementation for the primary prevention of heart disease found no statistically significant effects of selenium on both fatal and nonfatal cardiovascular events.

Although some research appears promising, there is not enough evidence to support the routine use of selenium supplements, especially in those who are obtaining enough from food to prevent heart disease at this time.


There is a notion that selenium may play a role in cancer prevention thanks to its ability to protect cells against DNA damage and mutations. However, the evidence around this remains conflicting.

According to a 2018 review of 83 studies, there is no solid research to suggest selenium from diet or supplements prevents cancer in humans.

In fact, some trials suggest that selenium supplementation may increase the risk of non-melanoma skin cancer and type 2 diabetes.

Thyroid disease

Selenium plays a key role in thyroid function. Some studies suggest that having optimal selenium levels can protect against thyroid disease and preserve overall health.

However, according to the Office of Dietary Supplements, additional research is needed to determine whether selenium supplements can treat or prevent thyroid disease.

Cognitive decline

Because serum selenium levels decline with age, marginal or deficient selenium concentrations may be associated with age-related declines in brain function. Experts believe this might be due to selenium’s antioxidant properties.

Still, more research is needed to determine if selenium supplementation can help treat or prevent age-related cognitive decline in older adults.

Overall, research remains conflicting regarding selenium supplementation and the effect of selenium on aging.

According to the 2018 review discussed above, most studies point to selenium supplementation having anti-aging properties and preventing aging-related diseases. However, more studies are needed to clarify its role.

At this time, there is no solid evidence that selenium supplementation benefits a person who is not at risk for deficiency.

A selenium deficiency is rare in the United States because of the selenium-rich soil found throughout North America.

Still, certain groups are at risk for selenium deficiency, including:

  • people living with HIV
  • people with kidney failure requiring hemodialysis
  • people who live in low-selenium regions, including some European countries, Russia, and China.

The risk is further increased for people living in low-selenium areas who follow a vegetarian or vegan diet.

Selenium deficiency can weaken cells’ ability to grow and divide, which can contribute to aging. It can also lead to delayed wound healing, cataract development, and loss of color.

Most adults need 55 micrograms (mcg) of selenium per day. Pregnant women, however, should consume 60 mcg. During lactation, selenium needs to further increase to 70 mcg.

Since the human body does not generate its own selenium, it is essential to get optimal amounts from the diet, in order for it to benefit overall health.

Thankfully, selenium is found in a wide variety of foods that can be easily incorporated into a person’s diet.

Because selenium is found in soil, its levels in food will be based on how much selenium was in the soil where the food was grown.

Brazil nuts, seafood, and organ meats are among the highest dietary sources of selenium. For example, one ounce of brazil nuts has 544 mcg of selenium or 989% of the recommended Daily Value (DV).

Other good dietary sources of selenium include:

  • yellowfin tuna
  • halibut
  • sardines
  • beef
  • ham
  • shrimp
  • cottage cheese
  • brown rice
  • boiled eggs
  • whole wheat bread
  • beans/lentils.

If a person consistently exceeds the recommended upper limit of 400 mcg of selenium through foods or supplements, it can cause adverse health effects.

One of the first signs of excessive selenium intake is a garlic smell on the breath and a metallic taste in the mouth.

Other signs of chronically high selenium intake are:

  • hair and nail loss or brittleness
  • skin lesions
  • mottled or decaying teeth
  • nausea
  • diarrhea
  • fatigue
  • irritability.

Taking megadoses of selenium can lead to acute selenium toxicity, which can lead to acute respiratory distress syndrome, severe gastrointestinal and neurological symptoms, kidney failure, cardiac failure, and — in extreme cases — death.

Selenium is an important mineral that is needed for many important functions within the body. There is also limited evidence that it may provide several different health benefits.

Selenoproteins are powerful antioxidants that can help protect against damage caused by free radicals that lead to aging and age-related health conditions.

At this time, there is no evidence that selenium supplements can slow or prevent aging. However, it is important to include optimal amounts of selenium in the diet because it does play a role in neutralizing free radicals and reducing inflammation, both of which can contribute to premature aging.

If you believe you have a selenium deficiency or are considering taking selenium supplements, be sure to speak with your healthcare provider.