Updated: Jul 8, 2020
Nuts are often lauded as healthy, providing a variety of vitamins, minerals, protein, and fat. However, Brazil nuts stand out from the crowd because they not only contain important vitamins and minerals including magnesium, copper, and zinc, but they also provide an abundance of selenium, a mineral that is essential for health but is often lacking in the modern diet. In fact, Brazil nuts contain the highest concentration of selenium of any food!
Selenium is critical for health because it:
acts as an important antioxidant, helping to reduce oxidative stress in the body (1)
aids in reproduction
is important for thyroid health
plays a role in DNA synthesis
protects against infection (2)
is associated with lower levels of inflammation
helps ensure proper immune system functioning
may be associated with reduced cancer risk (3), and
reduces risk of developing diabetes (4)
Oxidative stress can cause a variety of problems in the body, including cognitive impairment. Brazil nuts have been shown to restore selenium deficiency, and thus can have positive effects on people who have mild cognitive impairments (5). Consuming only 2 brazil nuts every day is enough to increase selenium levels and enhance glutathione peroxidase activity, an antioxidant enzyme that scavenges free radicals (6), which are unstable molecules that can cause destruction to cells. The thyroid has the highest selenium concentration of all organs in the body, and one's selenium status impacts thyroid disease risk. Selenium supplementation is often used to help regulate autoimmune thyroid disorders (e.g. Hashimoto's disease) (7).
Many studies have shown the positive effects of Brazil nuts on health:
1. One study found that consuming only 1 Brazil nut per day improved selenium levels and lipid profiles in obese women, which in turn reduced their heart disease risk (8).
2. Another study showed that 6 hours after healthy volunteers ate a single serving of Brazil nuts their LDL (the "bad" cholesterol) levels were significantly lower, and their HDL ("good" cholesterol) was significantly higher, again showing that the consumption of these nuts greatly improves serum lipid profiles (9).
3. Studies have shown that low levels of selenium in the diet is associated with depression, anxiety, and fatigue. These symptoms have been shown to decrease after selenium supplementation was implemented (10).
4. Another study showed that supplementation with Brazil nuts increased the selenium levels in patients with reduced T3 levels, and this supplementation improved their thyroid hormone levels (11).
Think of Brazil nuts as a daily supplement - you only need a small amount (1-3 depending on needs), and be cautious to not eat too many to avoid potential selenium toxicity. They do spoil quickly so it is important to store them in a cool, dark, dry place so they do not oxidize.
In summary, if you'd like to maintain thyroid health, reduce inflammation, improve serum lipid levels, reduce your risk of heart disease, and improve your mood, make sure to include a couple Brazil nuts in your diet daily!