This pesto is rich in selenium, which your thyroid needs to work properly. Make one jar and use it across the week: on toast, with eggs, stirred through roast vegetables, or tossed through pasta for the whole family. It takes 10 minutes, it’s vegetarian, and it makes about 1 cup, or 8 serves of 2 tablespoons.
What selenium does
Selenium is a trace mineral, which means you only need a small amount. For adult women the RDI is 60 µg a day.
- Thyroid: your thyroid makes a hormone called T4, which your body converts into T3, the active form that helps regulate your metabolism. The enzymes that do that conversion need selenium.
- Cell protection: selenium is part of antioxidant enzymes that break down harmful peroxides. These form as a normal part of metabolism and can damage cells.
- Immune system: selenium is needed for your immune system to function normally.
National surveys show only about 6% of Australian women don’t get enough selenium from food. The richest sources are seafood, meat, eggs and grain foods, and Brazil nuts, which contain far more than any other food. That’s why a few go a long way.
Why just 6 Brazil nuts
Brazil nuts are one of the richest food sources of selenium. On average, 100g of Brazil nuts contains about 1,900 µg of selenium, which works out to roughly 55 to 60 µg a nut. The RDI for adult women is 60 µg a day, so 1 or 2 nuts can cover it. The amount varies a lot between nuts, depending on the soil they grew in, so treat these figures as a guide.
Selenium also has an upper limit: 400 µg a day for adults, which the NHMRC has proposed lowering to 330 µg. A standard pesto uses about half a cup of nuts. Made entirely with Brazil nuts, that would come to around 1,250 µg of selenium in one batch.
So this pesto uses 6 Brazil nuts, about 340 µg of selenium across the whole jar, or roughly 40 µg in each 2-tablespoon serve. The pepitas give it body and add magnesium and zinc.
Ingredients
- 6 Brazil nuts
- ⅓ cup pepitas (pumpkin seeds)
- 2 cups basil leaves, loosely packed
- 1 handful baby spinach
- 1 small clove garlic
- ¼ cup finely grated parmesan, or 2 tablespoons nutritional yeast
- Juice of ½ lemon
- ⅓ cup extra virgin olive oil, plus extra to cover
- A pinch of salt
Method
- Toast the Brazil nuts and pepitas in a dry frying pan over medium heat for 3 to 4 minutes, until the pepitas start to pop. Let them cool for a few minutes.
- Blitz the nuts and pepitas in a food processor until finely chopped.
- Add the basil, spinach, garlic, parmesan or nutritional yeast, lemon juice and salt. Pulse to combine.
- With the motor running, pour in the olive oil until the pesto is as smooth as you like it. Taste and add more lemon or salt if needed.
- Spoon into a clean jar and pour a thin layer of olive oil over the top to keep it green.
Ways to use it across the week
- On toast: spread on wholegrain toast and top with sliced tomato or avocado.
- With eggs: spoon over scrambled, fried or soft-boiled eggs.
- Through roast vegetables: toss through roast pumpkin, broccoli or potatoes straight from the oven.
- For the family: toss the whole jar through 400g of cooked pasta with a drained tin of cannellini beans and a few handfuls of baby spinach. Serves 4, with about 85 µg of selenium a bowl.
Storage
Keep the pesto in the fridge, covered with a thin layer of oil, for up to 5 days. To keep it longer, freeze it in an ice cube tray and use the cubes within 3 months.
Swaps
- No pepitas: use sunflower seeds.
- Dairy free: use nutritional yeast in place of parmesan.
- Strictly vegetarian: many parmesans are made with animal rennet, so choose a vegetarian hard cheese or use nutritional yeast.
The takeaway: 6 Brazil nuts give this whole jar plenty of selenium while keeping each serve well under the upper limit. Make it once and use it all week.
The science behind this post:
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- If I eat too many Brazil nuts, will I get too much selenium? Nuts for Life, citing the Australian Food Composition Database (FSANZ). Read it here
- Nutrient Reference Values for selenium, NHMRC 2006. Read it here
- Draft recommendations for selenium, including the proposed upper limit of 330 µg a day, NHMRC public consultation. Read it here
- Draft recommendations for selenium, on its roles in thyroid hormone metabolism, antioxidant defence and immune function, NHMRC. Read it here
- Usual Nutrient Intakes, Australian Bureau of Statistics, 2011–12 and 2023. Read it here