According to Henderson, “Selenium is a vitamin that is good for peripheral conversion of thyroid hormone, so it’s good to help with the thyroid axis… It also is an antioxidant, so it helps with oxidative stress at the level of the thyroid.”
Meaning, it can fight free radicals and lower inflammation, which has been shown helpful for many people struggling with thyroid dysfunction. Brazil nuts, it turns out, are the highest known food source of selenium.
Sounds great! So why does Henderson mention the two- to three-nut limit? Well, Brazil nuts are so remarkably high in the trace element, that it’s actually quite easy to overdo it. The U.S. Department of Health & Human Services recommends 55 micrograms of selenium per day for adults, and just one Brazil nut can have between 68 and 91 micrograms—so just one nut already exceeds the recommendation.
Plus, overdoing the selenium can lead to some unfavorable symptoms (like rashes, dizziness, and nausea). So if you’re already getting selenium sources into your diet—think yellowfin tuna, halibut, sardines, and sunflower seeds—you might not want to add a whole bowl of Brazil nuts to the mix. According to research, eating just two Brazil nuts a day can help you get adequate levels of the nutrient. We repeat: Sometimes less truly is more.