Selenium is an essential mineral found in the soil, it has health benefits due to the roll it plays in various metabolism processes in our body. The Recommended Daily Allowance (RDA) is as little as 55 micrograms per day in adults of 19 years and up, amount easily attainable in the diet. Brazil nuts is the food source with highest amount of the mineral reaching 95.8 micrograms per nut.

Health Benefits

Selenium is an antioxidant, these are compounds in foods that prevent cell damage caused by free radicals. Free radicals are normal byproducts of processes like metabolism that occur in our body daily. Even though there’s bad reputation about them, free radicals are essential for health. They perform important functions, including protecting the body from disease. However, things like smoking, alcohol use and stress can cause an excess of free radicals. This leads to oxidative stress, which damages healthy cells. Oxidative stress has been linked to chronic diseases like heart disease, Alzheimer’s disease and cancer, as well as premature aging and the risk of stroke.

In addition to decreasing oxidative stress in the body, selenium may help lower the risk of certain cancers. This has been attributed to selenium's ability to reduce DNA damage and oxidative stress, boost the immune system and destroy cancer cells. A review of 69 studies that included over 350,000 people found that having a high blood level of selenium defended against certain types of cancer, including breast, lung, colon and prostate cancers. It’s important to note that this effect was only associated with selenium obtained through foods, not supplements.

A diet rich in selenium may help keep your heart healthy, as low selenium levels have been linked to an increased risk of coronary artery disease. In an analysis of 25 observational studies, a 50% increase in blood selenium levels was associated with a 24% reduction in coronary artery disease. Selenium may also lower markers of inflammation in the body, one of the main risk factors for heart disease. Additionally, it increased levels of glutathione peroxidase, a powerful antioxidant. This indicates that selenium may help lower heart disease risk by reducing inflammation and oxidative stress in the body. Oxidative stress and inflammation have been linked to atherosclerosis, or the buildup of plaque in the arteries. Incorporating selenium-rich foods into your diet is a great way to keep levels of oxidative stress and inflammation to a minimum.

Oxidative stress is believed to be involved in both the onset and the progression of neurological diseases like Parkinson’s, multiple sclerosis and Alzheimer’s disease. Several studies have shown that patients with Alzheimer’s disease have lower blood levels of selenium. Additionally, some studies have shown that selenium in both food and supplements may improve memory in patients with Alzheimer’s disease. One small study found that supplementing with one selenium-rich Brazil nut per day improved verbal fluency and other mental functions in patients with mild cognitive impairment. What’s more, the Mediterranean diet, which is rich in high-selenium foods like seafood and nuts, has been associated with a lower risk of developing Alzheimer’s disease.

Selenium is important for the proper functioning of the thyroid gland. In fact, thyroid tissue contains a higher amount of selenium than any other organ in the human body. This powerful mineral helps protect the thyroid against oxidative damage, also plays an essential role in the production of thyroid hormones. A healthy thyroid gland is important because it regulates metabolism and controls growth and development in the body. Selenium deficiency has been associated with thyroid conditions like Hashimoto’s thyroiditis, a type of hypothyroidism in which the immune system attacks the thyroid gland. An observational study of over 6,000 people found that low serum levels of selenium were associated with an increased risk of autoimmune thyroiditis and hypothyroidism.

The immune system keeps the body healthy by identifying and fighting off potential threats. These include bacteria, viruses and parasites. Selenium plays an important role in the health of the immune system. This antioxidant helps lower oxidative stress in the body, which reduces inflammation and enhances immunity. Studies have demonstrated that increased blood levels of selenium are associated with enhanced immune response. On the other hand, deficiency has been shown to negatively impact immune cells and may lead to a slower immune response. Studies have also associated deficiency with an increased risk of death and disease progression in people with HIV, while supplements have been shown to lead to fewer hospitalizations and an improvement in symptoms for these patients.

Asthma is a chronic disease that affects the airways that carry air in and out of the lungs. These airways become inflamed and begin to narrow, causing symptoms like wheezing, shortness of breath, chest tightness and coughing. Due to selenium's ability to lower inflammation in the body, some studies suggest that this mineral may be effective in reducing asthma-related symptoms. Research suggests that people who have asthma have lower blood levels of selenium. In fact, one study showed that asthmatic patients with higher levels of blood selenium had better lung function than those with lower levels.

While selenium toxicity is rare, it is important to stay close to the recommended amount of 55 mcg per day and never exceed the tolerable upper limit of 400 mcg per day. Brazil nuts contain a very high amount of selenium. Consuming too many could lead to selenium toxicity. However, toxicity is more likely to happen from taking supplements rather than from eating selenium-containing foods.