Selenium is a trace mineral that is essential for various bodily functions. It acts as a cofactor for several important enzymes involved in antioxidant defense and thyroid hormone metabolism. Selenium has recently been linked to joint health with rheumatoid arthritis sufferers having been shown to have lower levels in their blood.
However, it should be noted that in clinical trials of selenium against a placebo, it has been shown to have no noticeable effect in reducing joint pain. There have been some trials that suggest it may increase the efficacy of certain pain medications, but this is limited at best.
There’s more evidence to suggest selenium could have a protective effect, rather than doing anything to impact arthritis pain or symptoms.
The Role of Selenium in Joint Health
Research has shown that selenium may play a role in maintaining joint health and reducing the risk of certain joint conditions. One study conducted at the University of North Carolina at Chapel Hill found that higher selenium levels were associated with a reduced risk of knee osteoarthritis. 
The researchers observed that for every additional tenth of a part per million of selenium in the body, there was a 15 to 20 percent reduction in the risk of knee osteoarthritis. This suggests that selenium may have a protective effect on joint health, particularly in relation to osteoarthritis.
How Does Selenium Work for Joint Health?
The exact mechanisms by which selenium exerts its benefits on joint health are not fully understood. However, it is believed that selenium's antioxidant properties play a crucial role. Oxidative stress and inflammation are known to contribute to joint damage and the development of conditions like osteoarthritis.  Selenium, as an antioxidant, helps neutralize harmful free radicals and reduce inflammation, potentially protecting the joints from damage.  Selenium also contributes to the proper functioning of the immune system by regulating inflammatory responses and modulating the activity of immune cells, in other words it can help with inflammation.
Clinical Evidence for Selenium and Joint Pain
While the research on selenium and joint health is promising, when combined with other treatment, it is important to note that the clinical evidence supporting the use of selenium for joint pain is still limited. And the evidence for using it as a stand alone ingredient is none existent.
In one trial involving 40 participants over six months, selenium supplementation did not significantly improve disease severity, including pain, morning stiffness, and joint swelling.  Similarly, another trial with 55 participants over three months showed no significant difference in pain reduction, morning stiffness, or joint swelling between the selenium and placebo groups. 
However, one trial did report that participants in the selenium group had better arm movement and perceived better general health. 
It's worth noting that some trials have shown potential benefits of selenium when combined with other treatments. For example, a study combining selenium supplementation with the drug methotrexate, commonly used to treat RA, demonstrated a greater reduction in disease activity compared to methotrexate alone. Further research is needed to explore the potential synergistic effects of selenium and traditional RA treatments. 
Other Potential Benefits of Selenium
While the focus of this article is on selenium's relevance to joint health, it is important to highlight that selenium has broader health implications. Studies have suggested that selenium may have a protective effect against certain types of cancer, cardiovascular disease, and cognitive decline.  However, more research is needed to fully understand these potential benefits and their underlying mechanisms.
Dietary Sources of Selenium
Selenium is naturally present in a variety of foods, but the selenium content in plants depends on the selenium content in the soil where they are grown. Good dietary sources of selenium include Brazil nuts, fish, shellfish, whole grains, eggs, and poultry. Including a variety of selenium-rich foods in your diet can help ensure adequate selenium intake.
It's important to note that the selenium content in food can vary widely depending on factors such as geographic location, soil composition, and food processing methods. Therefore, it may be challenging to determine precise selenium intake from diet alone.
Selenium Supplements for Joint Health
If you're considering taking selenium supplements for joint health, it's probably not going to do much by itself. If a supplement you’re looking at contains selenium it can be a fine additional ingredient, but remember it's important to note that excessive selenium intake can have adverse effects, so it's essential to follow the recommended dosage guidelines. 
Recommended Dosage of Selenium
The daily recommended dietary allowance of selenium is 80-200 micrograms (μg). Most trials on selenium for arthritis used a dose of 200 μg. It is essential to adhere to the recommended dosage and not exceed it without medical supervision.
Potential Side Effects and Interactions
When taken in low or moderate doses, selenium is generally well-tolerated and unlikely to interact with other medications. However, high doses of selenium can be toxic and may cause gastrointestinal symptoms, liver and kidney problems, skin changes, and hair loss.
High Dose Selenium and Toxicity
High doses of selenium can lead to selenium toxicity, known as selenosis. Symptoms of selenosis may include gastrointestinal disturbances, hair loss, nail changes, and even neurological abnormalities.
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