Minerals

Selenium

A trace mineral with outsized impact on thyroid and immune health.

Selenium is critical for thyroid hormone metabolism, antioxidant defense via glutathione peroxidase, and DNA repair. Low selenium levels are linked to increased cancer risk, impaired immune function, and cognitive decline. The SU.VI.MAX trial found that selenium supplementation reduced cancer incidence in men by 31%.

Dosage

RDA: 55mcg for adults

Optimal for longevity: Researchers suggest 100-200mcg daily, though exceeding 400mcg can be toxic.

Deficiency signs

~15% of the global population is selenium-deficient; rates vary by region due to soil content

  • Weakened immune function
  • Thyroid problems or fatigue
  • Hair thinning or loss
  • Mental fog or difficulty concentrating

Top food sources

Brazil nuts (1 nut)96mcg
Yellowfin tuna (3 oz)92mcg
Halibut (3 oz)47mcg
Sardines (3 oz)45mcg
Turkey breast (3 oz)31mcg

Research

Rayman MP (2012). Selenium and human health. The Lancet, 379(9822), 1256-1268.

Track your selenium intake

Biohack logs selenium alongside 22 other longevity nutrients in every meal.

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