Selenium
Trace element with EFSA-authorised claims for thyroid and immune function; specific RCT signal for autoimmune thyroiditis.
Why
Selenium is an essential trace element with two EFSA-authorised health claims relevant here, for normal thyroid function and for normal immune function. Beyond baseline adequacy, several RCTs report reductions in thyroid peroxidase (TPO) antibody titres in Hashimoto's thyroiditis at 200 µg/day. The SELECT cancer-prevention trial in well-nourished adults showed no benefit and a non-significant prostate cancer signal, so supplementation above adequacy needs clinical context.
How it works
Cofactor for selenoproteins, glutathione peroxidase (antioxidant defence), thioredoxin reductase (redox balance), and iodothyronine deiodinases (conversion of T4 to active T3). In autoimmune thyroiditis, restoring selenoenzyme activity reduces oxidative thyrocyte damage that drives the antibody response.
Expected onset · TPO antibody reductions emerge over 3–6 months
How to take
Dosage
Maintenance: 55–100 µg/day. Hashimoto's RCTs: 200 µg/day for 3–6 months. Avoid sustained intake above 400 µg/day.
Timing
With food
On the label
Selenomethionine or selenium yeast (better retained than sodium selenite). Stated micrograms per serving.
Ideal for
Adults with autoimmune thyroiditis (Hashimoto's) and documented TPO antibodies; people with low selenium intake in low-selenium regions (parts of Europe and China).
Safety
Evidence
EFSA-authorised claims cover normal thyroid and immune function, the highest regulatory tier in EU food law. Wichman 2016 Thyroid meta-analysis (16 RCTs): 200 µg/day selenium reduced TPO antibodies at 3 and 6 months in autoimmune thyroiditis. Lippman 2009 SELECT (n=35,533): no cancer-prevention benefit in well-nourished men, narrow therapeutic window limits indefinite high-dose use.
- EFSA Reg 432/2012 authorised claims, 'Selenium contributes to normal thyroid function / normal function of the immune system'
- Wichman et al., Thyroid 2016, selenium supplementation significantly reduces TPO antibody concentrations in patients with chronic autoimmune thyroiditis: meta-analysis
- Lippman et al., JAMA 2009, SELECT: effect of selenium and vitamin E on prostate cancer (RCT)
Where to get it
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