Selenium May Prevent Alzheimer’s–But What Is It?

Prevent Alzheimer's
Dr. Geoffrey Harris, MD

Many researchers believe that Alzheimer’s is related to progressive oxidative damage to nerve cells by free radicals. A simple way to understand how brain cells can be injured by oxidation is to compare it to the oxidative damage of common metal wires which leads to rusting and poorer electrical transfer within the wire. Nerve cells, which act like wires in the brain, also become damaged by oxidation caused by free radicals. Over time, poor nerve cell functioning leads to memory difficulties and cognitive decline.

Selenium is a trace element that is beneficial in small amounts because it acts as an antioxidant in the body. Selenium combines with certain proteins to create enzymes that work with glutathione, one of the bodies’ main free radical scavengers. Glutathione works within cells to protect DNA and vital cell structures from free radical damage by absorbing high-energy electrons. Once glutathione absorbs a free radical, it must be regenerated by a group of enzymes called glutathione peroxidases–and this is where selenium comes in. Selenium empowers these peroxidase enzymes to regenerate the glutathione so that it can continue to protect the crucial parts of the cell. There’s hope that selenium may help prevent Alzheimer’s.

Two studies identified that selenium is crucial to preserving brain function and preventing age-related cognitive decline. One study of 2000 rural Chinese aged 65 and over found an association between low selenium levels and poorer performance on cognitive tests. This study, from the Indiana University Department of Medicine, looked at this group of Chinese individuals because over 70% of the study participants have lived in the same village since birth. By finding a group of people who have similar lifetime environmental exposures, the researchers found dietary variables that were associated with the development of cognitive decline. Another study from the University of Montpellier in France found that selenium levels tend to decrease with age in most people. However, the most important observation from this study was that individuals with the greatest drop in selenium levels also had the highest risk of cognitive decline.

Clearly, selenium is important for preserving brain health and promoting cognitive functioning. One of the richest sources of selenium is seafood and fish. Poultry is also a good source of this important antioxidant. Selenium can also be found in nuts and whole grains, but the plant levels of selenium depend on the soil content. For example, Brazil nuts grown in areas of Brazil with a high level of selenium can provide more than 100 micrograms of selenium in one nut, but Brazil nuts grown in selenium-poor soil can have ten times less. Grains grown in the United States are a good source of selenium, but fruits and vegetables tend to be poor sources.

The Recommended Daily Allowance (RDA) of selenium for adults is 55 micrograms (less than one Brazil nut grown in high-selenium soil). Selenium is available as a supplement, but selenium from food sources is better absorbed than selenium in supplements.

At SuperFoodsRx, we recommend taking a daily vitamin and mineral supplement that includes selenium at, or near, the RDA. We also recommend including whole grains, nuts, and fish in your regular diet. Furthermore, remember that antioxidants work in concert in the body. Many antioxidants, like vitamin C and E, also work with glutathione to protect cells. Try to eat a variety of fruits and vegetables, and include the SuperFoods in your diet to get a healthy mix of antioxidants.

Finally, while selenium is beneficial at levels near the RDA, high levels can be toxic and cause a condition called selenosis. Selenium toxicity can cause hair loss, stomach upset, brittle nails, irritability, nerve damage, and a garlic breath odor. The tolerable upper limit of selenium for adults is only 400 micrograms per day–so be careful with the Brazil nuts (if they are actually from Brazil). Remember, no antioxidant is a magic bullet, and the best approach to a healthy diet includes a variety of whole foods and SuperFoods that are rich in many antioxidants.

Sources: NCBI,

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