Benefits of Selenium

Evidence-Based Benefits

• Thyroid support — selenium is essential for the deiodinase enzymes that convert T4 to active T3; a 2010 Cochrane review found selenium supplementation reduced TPO antibodies in Hashimoto's thyroiditis
• Antioxidant defense — selenoproteins including glutathione peroxidase and thioredoxin reductase protect cells from oxidative damage
• Immune enhancement — selenium deficiency impairs both innate and adaptive immunity; supplementation in deficient populations improves immune cell function and vaccine response
• Cancer research — the SELECT trial (n=35,533) found no benefit for prostate cancer prevention, but observational data suggests adequate selenium status is associated with lower cancer risk
• Mood support — a 1991 Benton & Cook RCT found 100mcg selenium daily improved mood scores in participants with low baseline selenium

What the Research Says

Selenium research highlights the importance of baseline status. The Nutritional Prevention of Cancer (NPC) trial (Clark et al., 1996, n=1,312) initially showed a 52% reduction in prostate cancer with 200mcg selenium yeast daily, but this was a secondary endpoint. The subsequent SELECT trial (Lippman et al., 2009, n=35,533) found no cancer prevention benefit with selenomethionine in a selenium-replete population, and even suggested possible diabetes risk at 200mcg/day. For thyroid autoimmunity, a systematic review by Wichman et al. (2016, 16 studies) confirmed selenium supplementation reduces TPO antibody levels in Hashimoto's thyroiditis, though clinical significance remains debated.

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