Selenium
Part of antioxidant enzymes and needed to activate thyroid hormone; supports immunity.
If you are short of it
Possible signs
- Tiredness, low energy
- Hair thinning or loss
- Poor memory or concentration
- Muscle weakness
- Frequent infections
- Brittle or ridged nails
These signs are common and have many other causes. They are clues, not proof; a blood test and a doctor can tell.
Who is more at risk
People in regions with selenium-poor soil, dialysis patients, severe digestive disease, HIV, long-term tube or intravenous feeding.
Foods rich in Selenium
| Food | Serving | Amount | women 19–50 | men 19–50 |
|---|---|---|---|---|
| Brazil nut | 1 nut | 78 NIH | 142% | 142% |
| Tuna (canned, light) | 85 g, half a can | 68 | 124% | 124% |
| Mackerel | 100 g cooked | 52 | 95% | 95% |
| Sardines (canned, with bones) | 1 can (90 g drained) | 48 NIH | 87% | 87% |
| Couscous | 1 cup cooked | 43 | 78% | 78% |
| Shrimp | 85 g cooked | 42 NIH | 76% | 76% |
| Salmon | 100 g cooked | 41 | 75% | 75% |
| Whole-wheat pasta or noodles | 1 cup cooked | 36 NIH | 65% | 65% |
| Eggs | 2 large eggs | 31 NIH | 56% | 56% |
| Turkey breast | 100 g cooked | 30 NIH | 55% | 55% |
| Beef liver | 85 g cooked | 28 NIH | 51% | 51% |
| Cod or other white fish | 100 g cooked | 28 NIH | 51% | 51% |
| Chicken breast | 100 g cooked | 27 NIH | 49% | 49% |
| Lamb | 100 g cooked | 26 | 47% | 47% |
Unit: mcg. Share of the daily amount. Values marked NIH were checked against the food tables of the NIH Office of Dietary Supplements; the others are approximate and unchecked. Real foods vary with variety, brand, soil and cooking.
As a supplement
Selenomethionine or sodium selenite. One or two Brazil nuts a day can supply a day’s needs; a handful is too much.
Too much
Above 400 mcg a day: garlic breath, hair and nail loss, nerve problems (selenosis).
How much you need each day
| Group | Recommended | Upper limit |
|---|---|---|
| Infants 0–6 months | 15 | 45 |
| Infants 7–12 months | 20 | 60 |
| Children 1–3 years | 20 | 90 |
| Children 4–8 years | 30 | 150 |
| Children 9–13 years | 40 | 280 |
| Boys 14–18 years | 55 | 400 |
| Girls 14–18 years | 55 | 400 |
| Men 19–30 years | 55 | 400 |
| Women 19–30 years | 55 | 400 |
| Men 31–50 years | 55 | 400 |
| Women 31–50 years | 55 | 400 |
| Men 51–70 years | 55 | 400 |
| Women 51–70 years | 55 | 400 |
| Men over 70 | 55 | 400 |
| Women over 70 | 55 | 400 |
| Pregnant 14–18 years | 60 | 400 |
| Pregnant 19–30 years | 60 | 400 |
| Pregnant 31–50 years | 60 | 400 |
| Breastfeeding 14–18 years | 70 | 400 |
| Breastfeeding 19–30 years | 70 | 400 |
| Breastfeeding 31–50 years | 70 | 400 |
Unit: mcg. US/Canada Dietary Reference Intakes (National Academies), as summarised by the NIH Office of Dietary Supplements. Other countries’ values differ slightly. These are amounts for healthy people, not treatment doses.
Interactions
Take care · Iodine
Selenium is needed to turn thyroid hormone into its active form. Both iodine and selenium matter for the thyroid, and too much of either can upset it.
Page updated: 2026-10-08 · By Prof. E. Shalaan, Applied Sciences and AI (ASAI)