Selenium

硒

Place · Level 3

硒蛋白的活性中心 · 甲状腺脱碘酶 · 抗氧化系统的微量火花

Connected to · 5

synergy · 1

Vitamin E
GPx (a selenoenzyme) clears H₂O₂ in cytosol; α-tocopherol halts lipid peroxidation in membranes. Two phases, one ROS strategy.

cofactor · 4

Hashimoto's
Toulis 2010 meta: 200 µg/day × 6 months → anti-TPO ↓ ~30%. U-curve — don't megadose.
Iodine
Selenoprotein deiodinases (DIO1/2/3) are the sole T4→T3 converters; Se deficiency means tissue T3 is low even when T4 is adequate. Se also neutralizes H2O2 byproducts that would otherwise damage thyroid cells. Two pillars of thyroid function.
Immune
Selenocysteine sits at the active centre of glutathione peroxidase. When immune cells kill with an oxidative burst they oxidise themselves too — selenium is their self-protection kit.
Liver
Glutathione only neutralises peroxides through glutathione peroxidase (GPx), whose catalytic centre is a selenocysteine — there is a selenium atom embedded in the liver's busiest detox line.

Food · soil matters

Stop 1/5

食物 · 土壤决定

Selenium is the most typical case of 'soil geochemistry determines nutrition' — the same food can differ by tens of times in selenium content across regions. RDA 55 µg/day, UL 400 µg/day.

Main sources roughly:

Brazil nuts: average 70–90 µg / nut, but with huge variation (20–250 µg / nut even within the same bag, depending on the specific tree's soil) — a rare 'one nut affects your daily Se intake' foodSeafood (tuna, shrimp, sardines, salmon): 30–90 µg / 100 g, small batch variation, a stable sourceMeat + eggs: 10–40 µg / 100 g, depending on feedGrains: heavily dependent on local soil — US Great Plains wheat 50+ µg / 100 g, parts of China < 5 µg
From Heilongjiang to Yunnan in China, there is a low-selenium soil belt. Before the 1970s, Keshan disease (endemic cardiomyopathy) was rampant; after the government fortified table salt with selenium, incidence fell more than 90% — a modern example of a single trace element shaping regional health. Other global low-selenium regions include New Zealand (volcanic soil), parts of northern Europe, sub-Saharan Africa, and the US Northeast and Northwest.

In practice: diversifying food sources across regions is safer than fixing on a single staple; 1–2 Brazil nuts per day cover the RDA at low risk, but eating 10+ per day long-term is not advised (selenosis is real); people who regularly eat seafood, eggs, and meat are almost certainly not deficient.

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Educational content, not medical advice — consult a clinician.

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