Selenium Foods: Brazil Nuts, Eggs, Fish and the Too-Much Trap
Brazil nuts are a very concentrated source of selenium, and that same concentration is why they are an occasional food, not a daily one. Selenium is a trace mineral you need in small amounts, and most people get enough from ordinary meals. In the United States, true deficiency is rare, so the bigger practical question is how to avoid too much.
At a glance
- What it does: Helps make antioxidant enzymes and helps the enzymes that turn thyroid hormone into its active form.
- Richest foods: Organ meats and seafood, according to the Linus Pauling Institute.
- Brazil nuts: Very concentrated, and the amount depends on the soil where the tree grew.
- Deficiency: Rare with mixed diets in the United States.
- Too much: Hair and nail changes, nausea, irritability, fatigue and mild nerve effects.
Prefer to listen? This post as a 1 min video · Watch the video
Which foods have the most selenium?
The Linus Pauling Institute names organ meats and seafood as the richest food sources, followed by muscle meat from farmed animals. MedlinePlus lists fish, shellfish, red meat, chicken, eggs, grains and garlic as good sources, and calls Brazil nuts a very good source. Brazil nuts stand apart because their selenium depends on the soil where the tree grew.
A week of selenium-friendly eating
- Eat fish about twice a week, one of them oily, with a portion around 140 g. Prawns and other shellfish also supply selenium.
- Have one or two eggs on most days, cooked however you like them.
- Keep Brazil nuts to an occasional few, never a daily handful.
- Make lunch a mix of a katori of daal, a vegetable, a chapati and a little chicken, meat or egg when it suits you.
Why do Brazil nuts need a limit?
The nut is rich, and the amount swings. The Linus Pauling Institute notes that nuts grown on selenium-rich soil can carry roughly ten times the selenium of nuts from poorer soil. It also lists one ounce of Brazil nuts as above the adult upper limit for selenium. Because one ounce, about six kernels, from rich soil passes the adult limit on its own, keep the nut occasional and small. If you are comparing nuts more broadly, our almonds, walnuts and cashews comparison covers the everyday choices. Check your own country’s health service for the current upper limit.
What are the signs of too much selenium?
MedlinePlus lists hair loss, nail problems, nausea, irritability, fatigue and mild nerve damage as signs of selenosis, the condition caused by too much selenium. The Linus Pauling Institute adds digestive upset, skin rashes and a garlic-like breath odour, and it names hair and nail brittleness as the most common signs. Signs like these are a reason to keep Brazil nuts occasional rather than daily.
Does selenium matter for the thyroid?
In healthy people the thyroid is usually protected from changes in selenium supply, according to the Linus Pauling Institute. Selenium is needed for the enzymes that switch thyroid hormone into its active form, which is why it comes up in thyroid conversations. Trials in Hashimoto’s disease have measured antibody levels when selenium was given with thyroid hormone medicine. Some saw lower antibodies, but placebo-controlled evidence on symptoms is largely lacking. Food is not a treatment for a thyroid condition, so if you have one, talk to your doctor before changing how much Brazil nut or selenium-rich food you eat. For the separate iodine question, see our iodised salt guide.
The soil lottery check
Selenium in Brazil nuts depends on the soil the tree grew in, and a pack may not say where it came from. If the origin is printed, note it. If it is not, treat that bag as uncertain. Rotate the nut with fish, eggs and meat, so your week never depends on one unpredictable food.
See a doctor if you notice hair thinning or brittle nails, garlic-like breath, nausea, unusual tiredness or irritability, or numbness, especially after eating Brazil nuts often. Ask a doctor first if you are pregnant or breastfeeding, have a thyroid condition, or take regular medicines. If you have a nut allergy, skip Brazil nuts entirely.
Bottom line: Brazil nuts are a rich selenium food and an occasional one, not a daily staple. Fish, eggs and meat are usually enough for mixed diets, and deficiency is rare here. For selenium, variety beats a daily Brazil nut habit. More on minerals and food sits in our Vitamins and Minerals section.
Selenium foods: your questions answered
Which foods have the most selenium?
Organ meats and seafood are the richest sources named by the Linus Pauling Institute. Brazil nuts are very concentrated too, and their content depends on the soil. Eggs, chicken and red meat are steady everyday sources, according to MedlinePlus.
Are Brazil nuts good for the thyroid?
They contain selenium, but they do not treat a thyroid condition. The Linus Pauling Institute notes that trials in Hashimoto’s disease measured antibodies, and the evidence on symptoms is largely lacking. If you have a thyroid condition, ask your doctor before changing how often you eat them.
What are the signs of too much selenium?
The main signs are hair loss, brittle nails, nausea, irritability, fatigue and mild nerve effects, according to MedlinePlus. The Linus Pauling Institute also names garlic-like breath and skin rashes. If you notice these, see a doctor rather than guessing at the cause.
What are the signs of selenium deficiency?
Clear deficiency is rare in the United States, and the pages checked here do not list specific signs. MedlinePlus links it mainly to long-term intravenous feeding and to severe gut conditions that can affect absorption. Most people eating a mixed diet do not show it.
Is selenium from eggs and fish enough?
For most people eating a mixed diet, regular fish, eggs and meat are usually enough. Brazil nuts are a bonus for those who like them, not a requirement. If you are unsure, ask a dietitian to review your week.
Does selenium cause hair loss?
Too much selenium can cause hair loss, and MedlinePlus lists hair loss first among the signs of selenosis. Hair loss has many other causes, so a doctor should check it rather than assume food is to blame.
What are the side effects of Brazil nuts?
The main risk is too much selenium from eating them often, with garlic-like breath, nail and hair changes and nausea as warning signs. Anyone with a nut allergy should avoid them and read labels carefully.
Can Brazil nuts help Hashimoto’s?
Brazil nuts are not a treatment for Hashimoto’s. The trials gave added selenium and measured antibodies, and evidence on symptoms is largely lacking, so ask your doctor before changing anything.
Can vegetarians get enough selenium?
Eggs help lacto-ovo vegetarians. Anyone avoiding all animal foods should ask a doctor or dietitian about intake and whether a check is useful.
Should I take a multivitamin for selenium?
Food comes first for most people. For who might need a multivitamin, see our multivitamin verdict, and ask a doctor before starting one.