Where to find selenium, from Brazil nuts to fish.

Quick answer. The NHS lists Brazil nuts, fish, meat and eggs as good sources of selenium. In UK government food data (CoFID 2021), Brazil nuts lead at 254µg per 100g, followed by canned tuna (69µg), cooked mussels (66µg), grilled sardines (65µg), grilled mackerel (60µg) and baked cod (44µg). The NHS says men need 75µg a day and women 60µg, and that "If you eat meat, fish or nuts, you should be able to get all the selenium you need from your daily diet."

Which foods are high in selenium?

The NHS page on other vitamins and minerals names four good sources of selenium:

• Brazil nuts.
• Fish.
• Meat.
• Eggs.

For the amounts, the reference is the Composition of Foods Integrated Dataset (CoFID), the UK government's food composition tables. Selenium is measured in micrograms (µg), a thousandth of a milligram.

What is on a high selenium foods list?

These are CoFID 2021 figures, per 100g of food as described, from highest to lowest.

Two patterns stand out. Fish and shellfish fill most of the top half, which matches the NHS's fish and shellfish page, where shellfish are described as "a source of selenium, zinc, iodine and copper". And nuts vary widely: Brazil nuts carry more than 60 times the selenium of almonds per 100g, by our calculation.

Red meat is not the main source.

Selenium does not follow the zinc pattern. Lean rump steak has 10µg per 100g, against 29µg for lean pork loin and 44µg for baked cod. Offal is the exception, with lamb's kidney at 209µg.

How much selenium is in Brazil nuts?

CoFID gives 254µg of selenium per 100g of Brazil nut kernels, the average of 10 samples analysed. Weighed with their shells, the figure is 117µg per 100g, because the shell adds weight but is not eaten.

Nobody eats 100g at a sitting, so smaller weights are more useful. By our calculation:

• 10g of Brazil nut kernels holds about 25µg of selenium.
• That is about a third of the NHS figure for men (75µg) and about two fifths of the figure for women (60µg).

Brazil nuts are also high in magnesium, at 410mg per 100g in the same data. Our guide to magnesium-rich foods puts them at the top of that list too.

How do I get more selenium in my diet?

The Department of Health and Social Care advice on the NHS page is: "You should be able to get all the selenium you need by eating a varied and balanced diet that includes meat, fish or nuts." In practice, fish does the most work. The NHS says "A healthy, balanced diet should include at least 2 portions of fish a week, including 1 of oily fish", and that "A portion is around 140g."

Using that 140g portion and the CoFID figures, we calculated:

• Canned tuna in brine: about 97µg a portion.
• Grilled sardines: about 91µg a portion.
• Grilled mackerel: about 84µg a portion.
• Baked cod: about 62µg a portion.

Between fish meals, small habits add up:

• Keep eggs in the week. Boiled eggs carry 27µg per 100g.
• Choose pork or chicken. Lean grilled pork loin has 29µg per 100g and grilled chicken breast 16µg.
• Add a few Brazil nuts or cashews. Cashews carry 29µg per 100g, Brazil nuts far more.
• Use lentils and mushrooms. Boiled green or brown lentils have 18µg per 100g and raw white mushrooms 17µg.

Selenium on a vegetarian or vegan diet.

Without meat and fish, the NHS's other two sources remain: eggs for vegetarians, and Brazil nuts for everyone. Sunflower seeds (49µg per 100g), cashews, lentils and mushrooms add more. Bread, cheese and milk are low in selenium in the UK data, so they do not make up the difference on their own. If you have questions about your own diet, a GP or a registered dietitian can help.

How much selenium do you need a day?

The NHS says the amount you need is "75μg a day for men (19 to 64 years)" and "60μg a day for women (19 to 64 years)". The UK Government Dietary Recommendations keep both figures at 65 and over. For supplements, the NHS says: "Taking 350μg or less a day of selenium supplements is unlikely to cause any harm." Our guide to how much selenium you need a day has the figures for every age and the label numbers.

What does selenium do?

Selenium holds these authorised health claims in Great Britain, in their set wording:

• Selenium contributes to the normal function of the immune system.
• Selenium contributes to normal thyroid function.
• Selenium contributes to the maintenance of normal hair and nails.
• Selenium contributes to the protection of cells from oxidative stress.

Where Immufix fits.

Food comes first, and two fish meals a week do a lot of the work. Immufix is one scoop (25g) in around 200ml of water, once a day. Each scoop provides 75µg of selenium, which is 136% of the NRV of 55µg. By our calculation that matches the NHS figure for men and is a quarter more than the figure for women, and it is around a fifth of the NHS's 350µg line for supplements. Selenium contributes to the normal function of the immune system and to normal thyroid function. Every amount in the formula is on the science page.

The short version.

• The NHS's sources of selenium are Brazil nuts, fish, meat and eggs.
• Per 100g, Brazil nuts (254µg), brown crab meat (225µg), canned tuna (69µg), mussels (66µg) and sardines (65µg) lead the UK data.
• 10g of Brazil nuts holds about 25µg, by our calculation.
• A 140g portion of tuna, sardines or mackerel provides more than the NHS daily figure for women, by our calculation.
• The NHS says men need 75µg a day and women 60µg, and 350µg or less a day from supplements is unlikely to cause any harm.

Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle. If you have a medical condition, are pregnant, breastfeeding or taking medication, speak to your GP or pharmacist before taking any food supplement.