Selenium is an essential trace mineral that plays a crucial role in maintaining optimal health and wellness. Despite being needed in only small amounts, this powerful nutrient is involved in numerous vital bodily functions, from supporting your immune system to protecting against cellular damage.
Many people are unaware of selenium’s importance or may not be getting enough of this mineral in their daily diet. Understanding what selenium does for the body and the remarkable benefits it provides can help you make informed decisions about your nutritional intake.
This comprehensive guide explores seven science-backed selenium benefits and explains why this mineral deserves your attention as part of a healthy lifestyle.
What Is Selenium and Why Does Your Body Need It?
Selenium is a trace mineral that must be obtained through your diet, as your body cannot produce it naturally. While only small quantities are required, selenium is fundamental to numerous biological processes that keep your body functioning properly.
This essential mineral is incorporated into proteins to create selenoproteins, which act as powerful antioxidant enzymes. These selenoproteins help regulate thyroid hormones, DNA synthesis, reproduction, and protection from oxidative damage and infection.
The recommended dietary allowance (RDA) for selenium is 55 micrograms (mcg) per day for adults. Pregnant and breastfeeding women require slightly more, at 60 mcg and 70 mcg respectively.
1. Provides Powerful Antioxidant Protection
One of the most significant benefits of selenium is its exceptional antioxidant properties. Selenium helps form selenoproteins that function as potent antioxidants, defending your cells against free radical damage.
Free radicals are unstable molecules produced naturally during metabolism and as a response to environmental stressors like pollution, UV radiation, and tobacco smoke. While your body needs some free radicals for certain functions, an excessive accumulation can lead to oxidative stress.
Oxidative stress occurs when there’s an imbalance between free radical production and your body’s antioxidant defenses. This condition has been linked to accelerated aging and increased risk of chronic diseases, including cardiovascular disease, cancer, diabetes, and neurodegenerative disorders.
Selenium-dependent antioxidant enzymes, particularly glutathione peroxidase, work to neutralize excess free radicals before they can damage cellular structures, proteins, and DNA. By maintaining adequate selenium levels, you strengthen your body’s natural defense system against oxidative damage.
2. Supports Optimal Thyroid Function
The thyroid gland contains the highest concentration of selenium per gram of tissue compared to any other organ in your body. This fact alone highlights selenium’s critical importance for thyroid health.
Your thyroid gland produces hormones that regulate metabolism, energy production, body temperature, heart rate, and growth and development throughout life. Selenium is essential for the synthesis and metabolism of these thyroid hormones.
Specifically, selenium-containing enzymes help convert the thyroid hormone T4 (thyroxine) into its active form, T3 (triiodothyronine). Without sufficient selenium, this conversion process becomes impaired, potentially leading to thyroid dysfunction.
Research has shown that selenium deficiency is associated with an increased risk of thyroid disorders, including hypothyroidism and autoimmune thyroid conditions like Hashimoto’s thyroiditis. Adequate selenium intake helps protect thyroid tissue from oxidative damage and inflammation, supporting healthy thyroid function.
If you have concerns about your thyroid health, consult with your healthcare provider before making significant dietary changes or adding supplements to your routine.
3. Enhances Immune System Function
What does selenium do for the body’s defense mechanisms? Quite a lot, as it turns out. Selenium plays a vital role in supporting a robust and responsive immune system.
Your immune system relies on selenium to function optimally. This mineral influences both innate immunity (your body’s first line of defense) and adaptive immunity (the targeted immune response to specific pathogens).
Selenium enhances the production and function of white blood cells, including T cells, natural killer cells, and macrophages, which identify and eliminate harmful bacteria, viruses, and other foreign invaders. It also supports antibody production and helps regulate inflammatory responses.
Studies have demonstrated that individuals with higher selenium levels show improved immune responses, while deficiency can impair immune cell function and slow the body’s ability to fight infections.
Research has also indicated that selenium supplementation may benefit individuals with certain viral infections by supporting immune function and potentially reducing disease severity. However, selenium should complement, not replace, standard medical care for any health condition.
4. May Reduce Cancer Risk
Among the most studied benefits of selenium is its potential role in cancer prevention. Multiple mechanisms explain how selenium may help reduce cancer risk.
Selenium’s antioxidant properties help protect DNA from oxidative damage that can lead to cancerous mutations. Additionally, selenium may enhance the body’s ability to repair damaged DNA, slow cancer cell growth, and trigger apoptosis (programmed cell death) in abnormal cells.
Large observational studies have found associations between higher selenium blood levels and reduced risk of certain cancers, including prostate, lung, colorectal, and bladder cancers. A comprehensive review analyzing data from over 350,000 participants found that individuals with higher selenium status had significantly lower cancer risk.
It’s important to note that these protective effects appear strongest when selenium is obtained through food sources rather than supplements. The relationship between selenium and cancer prevention is complex and may depend on factors such as baseline selenium status, genetic variations, and the specific type of cancer.
While selenium shows promise for cancer prevention, it should never be used as a substitute for conventional cancer screening or treatment. Always work with qualified healthcare professionals for cancer-related concerns.
5. Promotes Heart Health and Cardiovascular Protection
Maintaining adequate selenium levels may help protect your cardiovascular system and reduce heart disease risk through several mechanisms.
Low selenium status has been linked to increased risk of cardiovascular disease in numerous population studies. Conversely, research suggests that higher selenium blood levels are associated with lower heart disease risk and improved cardiovascular outcomes.
Selenium supports heart health primarily by reducing oxidative stress and inflammation, both major contributors to atherosclerosis (the buildup of plaque in arteries). This plaque accumulation can restrict blood flow and lead to serious complications like heart attacks and strokes.
Studies have shown that selenium supplementation can decrease levels of C-reactive protein (CRP), a key marker of inflammation in the body. Selenium also increases glutathione peroxidase activity, which helps protect blood vessels and heart tissue from oxidative damage.
Additionally, selenium may help prevent the oxidation of LDL cholesterol, a critical step in the development of atherosclerotic plaque. Some research suggests selenium might also help regulate blood pressure, though more studies are needed to confirm this effect.
For optimal heart health, focus on obtaining selenium through a balanced diet rich in selenium-containing foods rather than relying solely on supplements.
6. Supports Cognitive Function and May Protect Against Mental Decline
Emerging research suggests that selenium plays an important role in maintaining brain health and cognitive function, particularly as we age.
The brain is particularly vulnerable to oxidative stress due to its high metabolic activity and abundant fat content. Selenium’s antioxidant properties help protect brain cells from oxidative damage that can contribute to cognitive decline and neurodegenerative diseases.
Several studies have found that individuals with Alzheimer’s disease and other forms of dementia tend to have lower selenium blood levels compared to cognitively healthy individuals. While this doesn’t prove that selenium deficiency causes dementia, it suggests a potential protective role.
Research has also indicated that higher selenium intake and blood levels are associated with better cognitive performance, including improved memory, verbal fluency, and overall mental function. Some studies have found that selenium supplementation may help slow cognitive decline in individuals with mild cognitive impairment.
Dietary patterns rich in selenium-containing foods, such as the Mediterranean diet, have been associated with better cognitive aging and lower Alzheimer’s disease risk. This suggests that obtaining selenium as part of a nutrient-dense diet may be particularly beneficial for brain health.
7. Selenium Benefits for Women: Reproductive Health and Beyond
Women have specific selenium needs related to reproductive health, fertility, and hormonal balance, making this mineral especially important throughout different life stages.
During pregnancy, adequate selenium intake is crucial for fetal development, particularly brain development. Selenium deficiency during pregnancy has been associated with increased risk of complications and may affect the baby’s long-term health outcomes.
Research suggests that selenium plays a role in female fertility by protecting reproductive tissues from oxidative damage and supporting proper ovarian function. Some studies have found that women undergoing fertility treatments with higher selenium levels may have better outcomes.
Selenium may also help manage symptoms of certain women’s health conditions. For instance, adequate selenium intake has been associated with reduced menstrual discomfort and may help regulate hormonal fluctuations.
Additionally, women are more likely than men to develop thyroid disorders, particularly autoimmune thyroid conditions. Given selenium’s crucial role in thyroid health, ensuring adequate intake is especially important for women’s endocrine health.
Pregnant and breastfeeding women should consult with their healthcare provider about appropriate selenium intake to ensure they meet their increased nutritional needs safely.
Best Food Sources of Selenium
The good news is that selenium is naturally present in a wide variety of delicious and nutritious foods. Incorporating selenium-rich foods into your regular diet is the best way to maintain adequate levels.
Top food sources of selenium include:
- Brazil nuts: The most concentrated source, with just one or two nuts providing more than the daily requirement
- Seafood: Yellowfin tuna, halibut, sardines, shrimp, and salmon are excellent sources
- Shellfish: Oysters, mussels, and crab provide substantial amounts
- Meat and poultry: Beef, chicken, turkey, and pork contain good amounts of selenium
- Eggs: One large egg provides about 15-20 mcg of selenium
- Whole grains: Brown rice, oatmeal, whole wheat bread, and other whole grains contribute to selenium intake
- Dairy products: Cottage cheese, milk, and yogurt contain moderate amounts
- Legumes: Beans, lentils, and chickpeas provide plant-based selenium
- Mushrooms: Especially shiitake and crimini varieties
- Seeds: Sunflower seeds and chia seeds offer selenium along with other nutrients
It’s important to note that the selenium content of plant-based foods can vary significantly depending on the selenium concentration in the soil where they were grown. Geographic variations in soil selenium levels mean that crops from selenium-rich regions will contain more of this mineral than those grown in selenium-depleted soils.
For this reason, eating a diverse diet with multiple selenium sources is the best strategy to ensure adequate intake regardless of where your food was grown.
How Much Selenium Do You Need?
Understanding the appropriate selenium intake for your age and life stage helps ensure you get sufficient amounts without exceeding safe limits.
The recommended dietary allowances for selenium are:
- Infants 0-6 months: 15 mcg
- Infants 7-12 months: 20 mcg
- Children 1-3 years: 20 mcg
- Children 4-8 years: 30 mcg
- Children 9-13 years: 40 mcg
- Adolescents 14-18 years: 55 mcg
- Adults 19+ years: 55 mcg
- Pregnant women: 60 mcg
- Breastfeeding women: 70 mcg
Most people in the United States consume adequate selenium through their regular diet and do not require supplementation. However, certain populations may be at higher risk for deficiency, including individuals with digestive disorders that impair nutrient absorption, those undergoing dialysis, and people living in regions with selenium-poor soil who eat primarily locally-grown foods.
Understanding Selenium Deficiency
While selenium deficiency is relatively uncommon in developed countries, it can occur and may lead to various health problems.
Symptoms and health effects of selenium deficiency may include:
- Weakened immune system and increased susceptibility to infections
- Fatigue and mental fog
- Hair loss or thinning
- Muscle weakness
- Infertility or reproductive issues
- Thyroid problems
- Increased risk of certain diseases
Certain medical conditions can increase the risk of selenium deficiency, including Crohn’s disease, celiac disease, and other conditions that affect nutrient absorption. People who rely on total parenteral nutrition (TPN) or who have undergone certain gastrointestinal surgeries may also be at higher risk.
If you suspect you may have a selenium deficiency, consult with a healthcare provider who can assess your status through blood tests and provide appropriate guidance.
Potential Risks of Excessive Selenium Intake
While selenium is essential for health, it’s possible to get too much of a good thing. Excessive selenium intake can lead to a condition called selenosis, which can cause serious health problems.
The tolerable upper intake level for selenium is 400 mcg per day for adults. Consuming amounts above this threshold regularly can result in selenium toxicity.
Signs and symptoms of selenium toxicity include:
- Garlic breath odor
- Metallic taste in the mouth
- Brittle nails
- Hair loss
- Nausea and vomiting
- Diarrhea
- Skin rashes or lesions
- Fatigue and irritability
- Nervous system abnormalities
- Mottled teeth
In severe cases, acute selenium toxicity can cause serious complications including respiratory distress, kidney failure, heart problems, and neurological damage.
Selenium toxicity is most likely to occur from excessive supplement use rather than food consumption. However, even food sources can contribute to toxicity if consumed in very large amounts. For example, eating many Brazil nuts daily could potentially lead to excessive selenium intake, as these nuts are extremely concentrated in selenium.
This is why it’s generally recommended to limit Brazil nut consumption to just one or two per day and to avoid taking high-dose selenium supplements unless specifically recommended and monitored by a healthcare provider.
Should You Take Selenium Supplements?
For most people eating a varied, balanced diet, selenium supplements are unnecessary and may even be counterproductive. Research suggests that the benefits of selenium are greatest when obtained through whole foods rather than isolated supplements.
However, selenium supplementation may be appropriate in certain situations:
- Diagnosed selenium deficiency confirmed by blood tests
- Malabsorption conditions that impair nutrient uptake
- Living in regions with severely selenium-deficient soil and limited access to diverse food sources
- Specific medical conditions under a doctor’s supervision
If you’re considering selenium supplements, consult with a healthcare provider first. They can assess whether supplementation is necessary, determine the appropriate dosage, and monitor for any adverse effects or interactions with medications.
Selenium can interact with certain medications, including cholesterol-lowering drugs, antacids, chemotherapy agents, and immunosuppressants. Always inform your healthcare provider about all supplements you’re taking.
Maximizing Selenium Absorption
To get the most benefit from dietary selenium, consider these tips for optimizing absorption:
Eat selenium-rich foods regularly: Consistency is key for maintaining adequate selenium levels. Include selenium sources in your diet several times per week.
Combine with vitamin E: Selenium and vitamin E work synergistically as antioxidants. Foods rich in both nutrients, or consuming them together, may enhance their protective effects.
Maintain adequate protein intake: Since selenium is incorporated into proteins to form selenoproteins, sufficient protein consumption supports selenium utilization.
Avoid excessive alcohol: Heavy alcohol consumption can impair selenium absorption and deplete body stores.
Cook foods appropriately: While selenium is relatively stable during cooking, some loss can occur. Steaming, baking, or light sautéing generally preserve selenium content better than boiling, which may cause some selenium to leach into cooking water.
The Bottom Line on Selenium Benefits
Selenium is a remarkable mineral that plays countless essential roles in maintaining your health and wellbeing. From its powerful antioxidant properties to its critical functions in immune support, thyroid health, heart protection, and cognitive function, selenium truly deserves recognition as a nutritional powerhouse.
The key to reaping selenium benefits lies in obtaining this mineral through a balanced, varied diet rich in selenium-containing foods. Seafood, Brazil nuts, meat, poultry, eggs, and whole grains offer excellent sources that can easily help you meet your daily needs.
While selenium is essential, remember that balance is crucial. Both deficiency and excess can cause health problems, so aim for the recommended intake of 55 mcg per day for adults through food sources rather than high-dose supplements.
By understanding what selenium does for the body and making informed dietary choices, you can harness this mineral’s protective powers to support long-term health and vitality. As with any significant dietary changes or health concerns, consult with a qualified healthcare professional for personalized guidance tailored to your individual needs.
Sources:
- National Institutes of Health – Office of Dietary Supplements: Selenium Fact Sheet
- PubMed Central: Selenium and Human Health
- PubMed Central: The Role of Selenium in Thyroid Hormone Metabolism
- PubMed Central: Selenium and Oxidative Stress
- USDA FoodData Central
- PubMed Central: Selenium in the Immune System
- World Health Organization: Trace Elements in Human Nutrition