Selenium
Selenium supports antioxidant enzymes, thyroid function and immune support. Food-first intake is preferred; supplements should be matched to diet, health context, and safety considerations.
Overview
Biological role
Selenium supports antioxidant enzymes, thyroid function and immune support.
Mechanism of action
Selenium contributes to normal physiology through nutrient-specific enzyme, structural, signaling, transport, or regulatory roles described in authoritative nutrition references.
Chemical forms
Selenium may appear in foods and supplements in different chemical forms. Selection should consider the nutrient form, dose, tolerance, and health context.
Quick answers before choosing a supplement
Chemical forms and absorption
Common forms
Selenium may appear in foods and supplements in different chemical forms. Selection should consider the nutrient form, dose, tolerance, and health context.
Absorption context
Absorption can vary with food composition, supplement form, dose, and timing. Food-first intake is preferred when possible.
Clinical use
Established essential nutrient roles should be separated from supplement benefit claims. Supplement use is most appropriate when there is inadequate intake, increased need, deficiency risk, or a clinical indication.
Absorption and action pathway
What to take with, and what to avoid
Works Well With
Avoid / Use Caution
Best time to take
Frequently asked questions
When is the best time to take Selenium?
Use with meals if the supplement irritates the stomach; separate from medicines or competing minerals when needed.
Can Selenium be taken with coffee or milk?
Some minerals compete with foods, drinks, or medicines. Separate timing is useful when treating a deficiency.
Who should be careful with Selenium?
Pregnant or lactating people, older adults, children, people with chronic diseases, and people taking regular medicines should use supplements with professional guidance.
Food and Intake
| Age / group | Male | Female | Pregnancy | Lactation | Upper limit |
|---|---|---|---|---|---|
| 1-3 years | 20 | 20 | – | – | UL 90 |
| 4-8 years | 30 | 30 | – | – | UL 150 |
| 9-13 years | 40 | 40 | – | – | UL 280 |
| 14-18 years | 55 | 55 | 60 | 70 | UL 400 |
| 19+ years | 55 | 55 | 60 | 70 | UL 400 |
International reference intake comparison
| Country / authority | Common reference value |
|---|---|
| USA / NIH-FNB | RDA 55 mcg; pregnancy 60; lactation 70; UL 400 |
| Europe / EFSA | AI adults about 70 mcg; UL latest 255 mcg |
| Australia-New Zealand / NRV | RDI 70/60 mcg men/women |
| Thailand / Thai FDA | Thailand: use Thai RDI and Thai FDA / Ministry of Public Health regulations for labeling and supplement products. Do not interpret labeling values as therapeutic doses; product-specific limits must be checked against the latest notification and formula. |
This table compares reference-intake frameworks across authorities. Values may use different terms such as RDA, AI, PRI, or NRV and should not be merged into one universal dose.
Food source comparison for Selenium
| Food | Serving amount | Selenium | %DV | %DV bar | Servings to reach 55 mcg |
|---|---|---|---|---|---|
| Brazil nuts | 1 oz | 544 mcg | 989% | 0.1 | |
| tuna | 3 oz | 92 mcg | 167% | 0.6 | |
| halibut | 3 oz | 47 mcg | 85% | 1.2 | |
| sardines | 3 oz | 45 mcg | 82% | 1.2 | |
| ham | 3 oz | 42 mcg | 76% | 1.3 | |
| egg | 1 egg | 15 mcg | 27% | 4 |
Food values are practical comparison values. Actual content varies by variety, preparation, fortification, and serving size.
Safety
Deficiency
Inadequate Selenium intake or absorption may affect body systems related to antioxidant enzymes, thyroid function and immune support. Deficiency risk depends on diet, absorption, medical conditions, and life stage.
Excess and toxicity
High intake can cause selenium toxicity; Brazil nuts can be very high.
Precautions
High intake can cause selenium toxicity; Brazil nuts can be very high.
Special populations
Pregnant or lactating people, older adults, children, people with chronic diseases, and people taking regular medicines should use supplements with professional guidance.
Fast risk map
LOW: insufficient intake
Inadequate Selenium intake or absorption may affect body systems related to antioxidant enzymes, thyroid function and immune support. Deficiency risk depends on diet, absorption, medical conditions, and life stage.
UL: excess intake
High intake can cause selenium toxicity; Brazil nuts can be very high.
Precautions: interactions and timing
High intake can cause selenium toxicity; Brazil nuts can be very high.
SP: special populations
Pregnant or lactating people, older adults, children, people with chronic diseases, and people taking regular medicines should use supplements with professional guidance.
Interactions and Clinical Context
Drug interactions
Potential interactions depend on the nutrient, supplement dose, medicines used, and medical conditions. People using regular medicines should check interaction guidance from clinical sources or ask a clinician.
Food interactions
Absorption can vary with food composition, supplement form, dose, and timing. Food-first intake is preferred when possible.
Clinical notes
Established essential nutrient roles should be separated from supplement benefit claims. Supplement use is most appropriate when there is inadequate intake, increased need, deficiency risk, or a clinical indication.
Evidence level
High for essential nutrient role; nutrient-specific supplementation benefits depend on baseline status and clinical context.