Selenium (L-Selenomethionine)

Thyroid & immunity

Function & benefits

A trace mineral that is part of about 25 selenoproteins, including the antioxidant enzyme glutathione peroxidase and the enzymes that convert thyroid hormone T4 into T3; it contributes to normal immune and thyroid function and the protection of cells from oxidative stress (EFSA).

Dosage & how to use

Recommended dose	55–100 µg daily
Best time to take	With breakfast or lunch
Frequency	Once daily

Best forms to choose

L-selenomethionine or selenium yeast, with absorption above 90% compared with inorganic selenite and selenate.

Important warnings

Updated EFSA upper limit (2023): 255 µg a day from all sources for adults

Selenium toxicity causes garlic breath, hair loss and brittle nails

Avoid high doses over long periods without testing

Drug interactions

It may interfere with some chemotherapy drugs and with the statin–niacin combination; consult your doctor. There is no proven conflict with vitamin C at moderate doses.

View in the supplements guide

Related supplements

Scientific references

EFSA Scientific Opinion on the Tolerable Upper Intake Level for selenium (2023)
NIH Office of Dietary Supplements (ODS): Selenium Fact Sheet

📚 Published sources and research: European Food Safety Authority (EFSA) • National Institutes of Health (NIH - ODS) • PubMed / Cochrane databases

Content last updated: 17 October 2026 · Based on published sources and research (EFSA / NIH / PubMed)

⚖️ Medical disclaimer: The information and data provided here are for health education and nutritional guidance only. They are not a medical diagnosis and never replace a direct consultation with your doctor or pharmacist. Always consult your doctor before starting any supplement, especially during pregnancy or breastfeeding or when taking long-term medication.