Does Selenium Reduce Inflammation? A Deep Dive into the Science

November 17, 2025 •

4 min read

Selenium is an essential trace element that plays a vital role in synthesizing selenoproteins, many of which are powerful antioxidants and crucial for proper immune function. Research suggests that adequate selenium status is linked to reduced inflammation, primarily by helping to combat oxidative stress.

Quick Summary

Selenium works as a powerful antioxidant by supporting selenoproteins, which regulate oxidative stress linked to inflammation. Studies suggest it can reduce inflammation, especially in deficient individuals or those with conditions like autoimmune thyroiditis, asthma, and critical illness. Benefits are most apparent with sufficient intake, and high-dose supplementation requires caution.

Key Points

Powerful Antioxidant: Selenium helps create potent antioxidant enzymes, like glutathione peroxidase (GPx), that protect cells from damage caused by free radicals and oxidative stress.
Combats Inflammation Drivers: By reducing oxidative stress, selenium helps to mitigate a primary driver of inflammation and supports a balanced immune response.
Deficiency Magnifies Risk: A low selenium status has been directly linked to increased inflammation and a higher risk of inflammatory and autoimmune conditions.
Beneficial for Some Conditions: Research shows potential anti-inflammatory benefits for certain autoimmune diseases (Hashimoto's thyroiditis) and in acute states like sepsis, particularly in deficient individuals.
Dietary Sources Preferred: A balanced diet with selenium-rich foods, including Brazil nuts and seafood, is the safest and most effective way to maintain healthy levels.
Supplements Require Caution: While supplements can address deficiencies, the therapeutic window is narrow, and high doses carry a risk of toxicity (selenosis).

The Core Mechanism: How Selenium Fights Inflammation

At the heart of selenium’s anti-inflammatory properties is its role in producing powerful antioxidant enzymes known as selenoproteins, such as glutathione peroxidases (GPx) and thioredoxin reductases (TrxR).

Combating Oxidative Stress: Inflammation is often driven by oxidative stress, an imbalance between free radicals and the body's antioxidant defenses. By helping produce GPx, selenium neutralizes damaging free radicals like hydrogen peroxide, thereby reducing cellular damage and mitigating the inflammatory cascade.
Regulating Immune Response: Selenium also modulates the immune system. Selenoproteins can influence key signaling pathways like NF-κB, which controls the expression of pro-inflammatory cytokines. Adequate selenium levels can lead to a more balanced immune response, while a deficiency can lead to an overactive, inflammatory state.

The Connection Between Selenium Deficiency and Increased Inflammation

Numerous studies have identified a strong link between low selenium status and elevated inflammatory markers and chronic inflammatory conditions. The level of selenium available to the body is influenced by both dietary intake and the selenium content of the soil where food is grown.

For example, deficiencies have been reported in critically ill patients, often associated with poor outcomes and higher mortality rates. In these cases, the body’s antioxidant system is overwhelmed, and restoring selenium levels can help the body combat systemic inflammation. Similarly, patients with Inflammatory Bowel Disease (IBD) often show significantly lower selenium levels, and supplementation may help manage inflammation in the gastrointestinal tract.

Evidence for Selenium's Role in Specific Conditions

Autoimmune Thyroid Disease

For conditions like Hashimoto's thyroiditis, where the immune system attacks the thyroid gland, several studies have investigated selenium's role. Evidence suggests that supplementation may help reduce levels of anti-thyroid peroxidase (TPOAb) antibodies and improve overall well-being. However, this is primarily in cases where a pre-existing selenium deficiency is present, and high doses can be detrimental.

Rheumatoid Arthritis (RA)

Early research suggested potential benefits of selenium supplementation for RA patients. Some trials showed improvements in joint symptoms, but results have been inconsistent across studies. This highlights the complex nature of chronic inflammatory diseases and the need for more targeted research to understand which patient subgroups might benefit most.

Asthma

Since asthma is associated with inflammation and oxidative stress in the airways, researchers have explored selenium's potential benefit. Some studies show that asthmatic patients with higher blood selenium levels tend to have better lung function. However, as with RA, research into supplementation has yielded conflicting results, and its role is not yet fully understood.

Critical Illness and Sepsis

In critically ill patients, especially those with sepsis, low selenium levels are common. The administration of selenium, particularly intravenously in hospital settings, has shown some promise in reducing certain inflammatory markers. The effects vary depending on the dosage, route, and the patient's baseline status, indicating it is not a one-size-fits-all solution.

How to Get Enough Selenium

Rather than relying solely on supplements, a balanced diet is the best way to maintain healthy selenium levels. Key sources of this mineral include:

Brazil Nuts: Often cited as one of the best sources, a single Brazil nut can provide more than the daily recommended intake.
Seafood: Fish like tuna, halibut, and sardines are excellent sources.
Meat and Poultry: Chicken, turkey, and lean beef contribute significantly to selenium intake.
Eggs: The yolk, in particular, contains a good amount of selenium.
Grains: Rice, especially brown rice, and whole-grain bread and pasta provide selenium.

Comparison of Selenium Sources: Food vs. Supplements


Feature	Food Sources	Supplements
Natural Form	Organic forms like selenomethionine and selenocysteine, highly bioavailable.	Can be organic (selenomethionine, selenium yeast) or inorganic (sodium selenite, sodium selenate).
Risk of Excess	Extremely low risk from diet alone, though Brazil nuts require caution.	Higher risk of toxicity (selenosis) if taken at high doses or for extended periods.
Absorption	Can be influenced by soil quality and bioavailability, but generally well-absorbed.	Varies by form and individual; selenomethionine is generally well-absorbed.
Overall Health	Provides a synergistic blend of nutrients and fiber, supporting overall wellness.	Can provide a targeted dose to correct a deficiency, but lacks the broader nutritional benefits of food.

Conclusion

Selenium's ability to reduce inflammation is strongly supported by its crucial role as an antioxidant. By aiding in the production of key selenoproteins, it helps neutralize damaging free radicals and modulate the immune system, both of which are critical for controlling inflammatory responses. While it appears to offer significant benefits, particularly for individuals with documented deficiencies or specific autoimmune conditions like thyroiditis, it is not a cure-all. Adequate intake is best achieved through a balanced diet rich in selenium-containing foods like Brazil nuts and seafood. Supplementation should be approached with caution due to the risk of toxicity (selenosis) and should ideally be overseen by a healthcare professional. Ultimately, maintaining a sufficient selenium status is a key component of a healthy, anti-inflammatory lifestyle.

For further reading on the complex role of selenium in health and disease, you can explore detailed research available on the National Institutes of Health website at https://www.ncbi.nlm.nih.gov/.

Frequently Asked Questions

Selenium's primary anti-inflammatory mechanism is its role as a key component of selenoproteins, such as glutathione peroxidases (GPx). These enzymes are powerful antioxidants that neutralize harmful free radicals, thereby reducing the oxidative stress that drives inflammation.

While selenium supplementation has been shown to reduce thyroid antibody levels and improve symptoms in some individuals with autoimmune thyroiditis (Hashimoto's), particularly those with a deficiency, it is not a cure. High doses can be harmful, so supplementation should be managed by a healthcare provider.

For most people, getting selenium from food is safer and more beneficial. Whole foods offer a complex blend of nutrients, and the risk of toxicity from food is very low. Supplements carry a higher risk of overdose and should be used cautiously, primarily to correct a known deficiency.

Some of the best food sources of selenium include Brazil nuts, seafood (like tuna and halibut), lean meats, eggs, and whole grains. The selenium content in plant-based foods can vary depending on the soil's mineral content.

Excessive selenium intake can lead to a condition called selenosis. Symptoms include hair loss, brittle nails, gastrointestinal issues, and nervous system problems. Extremely high doses can be dangerous and potentially fatal.

Research suggests that low blood selenium levels are linked to increased oxidative stress in asthmatic patients, and some studies indicate a potential benefit from supplementation. However, the evidence is conflicting, and more research is needed to fully understand its role.

The recommended dietary allowance for selenium is generally around 55 micrograms (mcg) per day for adults, though it can vary. The tolerable upper limit is 400 mcg daily, and exceeding this significantly or for a long time increases toxicity risk.