Found throughout most of the north-eastern regions of South America, Brazil nut trees are among the oldest and largest trees found in the Amazon rainforest. The trees are often over 30 meters tall and approximately 2 meters wide, with a lifespan of anything between 500 to 1000 years.
And the actual fruit is impressive too (see below). Weighing around 2kg and roughly the size of a coconut, the entire capsule has a woody outer shell containing within up to 24 individual wedge-shaped seeds. These seeds are what we know as Brazil nuts.
Having been discovered by Spanish rovers in the mid 16th century, the Brazil nut was introduced first to Europe and later to the United States during the 1800s. An excerpt from W.J. Young’s 1911 article entitled ‘The Brazil Nut’ includes a beautiful and quirky translation of the first documented description of Brazil nuts:
‘A compound nut the size of a child’s head…. Divided internally into four cells, each of which encloses several nuts… with a husk of green colour, smooth and shining.’
Hmmmm, I’m sure it sounded more poetic in its original Spanish.`
Brazil Nuts & Selenium
Everyone knows Brazil nuts are high in selenium, but how important really is selenium in the body? It’s actually crucially important throughout every life stage.
Like all minerals however, too much or too little can also be an issue. You’d think because selenium is a trace mineral, which means it’s required in only small amounts, that we’d be getting sufficient levels in our diet.
But the truth is that most U.S., Australian and New Zealand soils are depleted of selenium, as well as other important minerals due to the use of harsh agricultural methods over the last century.
The mineral content of a plant, fruit or vegetable depends entirely upon the soil in which in grows. Minerals are absorbed within the root system of the plant and help with various metabolic functions and defences. Selenium accumulates easily in cruciferous vegetables like broccoli and cabbage. It’s also found in garlic, but most abundantly in Brazil nuts.
The soil in regions that naturally product Brazil nuts are rich in selenium. The gentler farming methods as well as other environmental factors contribute to their replete mineral levels in the soil. This is why it’s important to source Brazil nuts from their native growing regions in South America.
Brazil Nuts and Thyroid Health
While iodine is the essential nutrient for thyroid health, what most people, including health professionals don’t always consider is the role of selenium. Selenium forms part of an enzyme which converts thyroxine (T4) to the biologically active thyroid hormone, triiodothyronine (T3). This is a major consideration in a naturopathic assessment of thyroid function, and ultimately means if you don’t have enough selenium, your body can’t convert T4 into T3.
A 2015 clinical trial evaluating the effects of Brazil nut consumption on thyroid hormones saw significant improvements in T3 levels in participants at the end of the study period. Thyroid hormones influence tissue growth, a healthy reproductive system, heart rate, body temperate and the nervous system.
Brain and Nervous System Health
Chronic inflammation is a process in the body which causes cell damage, tissue breakdown and eventually chronic disease. Humans have a unique and important innate ‘antioxidant system’ which recognises and resolves all the ‘little fires’ that continually occur within our body.
Areas of the body that are particularly sensitive to widespread inflammation (oxidative stress) are the brain and nervous system. Selenium is an essential mineral required for this antioxidant defence system to work properly.
A controlled trial examining a small group of elderly participants with mild cognitive impairment investigated the effects of Brazil nut consumption, with the intention of increasing selenium intake to support antioxidant function and brain health. One single Brazil nut was consumed daily for 6 months.
At the end of the study period, participants had vastly improved verbal fluency and motor function in the Brazil nut group compared to the control group.
Brazil Nuts and Cardiovascular Health
Other clinical trials have demonstrated that servings of 13g, 20g and 50g of Brazil nuts have cholesterol-lowering effects which benefit the cardiovascular systems in otherwise healthy adults. Interestingly, the results of these trials showed acute (6 hr post-prandial) and long term (30 days and 90 days) improvements in HDL cholesterol within blood results of participants following consumption of these nuts.
Brazil Nuts & Health Risks
While selenium is important and Brazil nuts are indeed the richest dietary source available, there are risks associated with consuming too many. The National Health and Medical Research Council’s nutrient reference values state the RDI for selenium for adults is around 60mcg per day, with an upper limit of 400mcg per day. For pregnancy, lactation, children and the elderly, as well as if you suffer from thyroid disease, the recommendations vary again.
Selenium toxicity is known as selenosis. In most cases, selenium toxicity occurs as a result of consuming excess amounts from synthetic sources. Coal mines are one example of extreme selenite and selenate exposure leading to selenosis. Symptoms of selenosis include dizziness, extreme gastrointestinal problems, irritability and nervousness and widespread joint pain.
It is unlikely to be experiencing symptoms such as these from Brazil nut consumption, however if you have concerns it’s always wise to check with your primary care provider.
Realistically Brazil nuts are considered safe to consume as a healthy, natural source of elemental selenium. Between 2-6 brazil nuts per day would qualify as enough selenium for a healthy adult.
How to eat more Brazil Nuts
I feel Brazil nuts have been known as the unwanted addition to the mixed nuts bowl. I’ve too often had a ‘why are you even here?’ look on my face when I’ve bypassed them to get to a cashew or almond. So, instead of suggesting Brazil nuts as a topping or afterthought, I’ve found a recipe that includes Brazil nuts – intentionally. Adapted from one of my favourite chefs, Yotam Ottolenghi. Here’s a classic granola recipe for you to enjoy!
40g Brazil nuts
40g cashew nuts
300g rolled oats
60g pumpkin seeds
60g sunflower seeds
100g dried apricots, roughly chopped
60g dried cranberries or dried cherries
60g dried blueberries
120ml raw honey
60ml maple syrup
3 tbsp. olive oil
2 tbsp. sunflower oil
¼ tsp. salt
- Preheat oven to 140 deg Celsius.
- Chop all the nuts and add to large mixing bowl. Mix in oats and seeds, set aside.
- In a small saucepan combine all syrup ingredients. Stir gentle and warm over a low heat.
- Pour syrup over granola mixture and stir well to combine.
- Line a large baking sheet with baking paper and spread the granola out evenly to 1cm thick.
- Bake for 40 minutes turning a few times to ensure it is evenly toasted.
- Finally, once granola is baked and slightly cooled, add the dried fruit and stir to combine.
- Once cooled, completed transfer to a container and store for up to 2 weeks.
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