The richest food source of selenium
Brazil nuts
Whole, raw or dry-roasted, unsalted
Big, creamy nuts with more selenium than any other common food. A single nut can carry more than a day's worth.
Evidence C
What it is
The seed of a tall Amazon rainforest tree, gathered from the wild rather than farmed. Brazil nuts are rich and creamy, with a lot of fat and some protein and magnesium. They're best known for selenium: the NIH lists about 544 mcg in an ounce (6 to 8 nuts), against an adult daily need of 55 mcg. Nuts from selenium-rich soils carry far more than nuts from poor soils, so any per-nut figure is an average.
How to choose
- Whole nuts, raw or dry-roasted, with no added oil.
- Unsalted, or lightly salted.
- Plump and pale inside; skip any that look shrivelled, dark or smell like paint.
- A small bag you'll finish: they're high in fat and go rancid. Keep them in the fridge once open.
How to use it
- As a snack alongside other nuts, rather than by the handful on their own.
- Chopped over yoghurt, porridge or salad.
- Blended into nut milk or pesto.
Watch out
- Tree nut allergy.
- Selenium builds up, and too much causes selenosis: garlic breath, hair and nail loss, nausea and nerve problems. The adult upper limit is 400 mcg a day from all sources, which a small handful of Brazil nuts can pass.
- If you take a multivitamin or supplement with selenium, count it too, and ask your doctor or pharmacist before adding Brazil nuts every day.
The evidence Grade C
Mostly mechanistic or observational. It's food, so that's fine; we just say so.
Brazil nuts reliably raise selenium levels: in a 12-week trial, two a day worked as well as a selenium supplement. Selenium is part of enzymes the body uses for DNA synthesis and to protect cells from oxidative damage. That doesn't make more of it better for cancer: a Cochrane review of trials and long-term studies found no evidence that getting more selenium, from food or supplements, means fewer cancers, and a large trial in people who'd had colon polyps removed found selenium didn't stop new ones forming and may have raised the risk of type 2 diabetes. How much selenium is in a nut depends on the soil it grew in, so the amount varies widely.
- NIH Office of Dietary Supplements: Selenium fact sheet
- Trial: Brazil nuts and selenium status (Thomson et al., 2008)
- Cochrane review: selenium and cancer (Vinceti et al., 2018)
- Trial: selenium and colon polyps after removal (Thompson et al., 2016)
- Selenium varies nut to nut by region (Silva Junior et al., 2017)
Last reviewed 2026-10-23.