One of your brain’s biggest enemies is oxidative stress – the buildup of toxic molecules called free radicals that can oxidize and destroy neurons and the network connections among brain cells. When free radicals overwhelm the brain’s antioxidant defenses, your memory and ability to think straight take a hit.

To keep this potential disaster under control — and your mental function at its peak — the brain especially depends on one mineral to produce the enzymes that help eliminate free radicals.

The crucial mineral in question – selenium.

Selenium is so important to the brain’s well-being that if it runs short it robs the rest of the body to get the selenium it needs.1

And researchers agree that having sufficient selenium in your diet is important during your entire life (it also plays an important role in cancer prevention). You can’t wait until you’re a senior citizen and then think you can quickly make up a selenium shortfall.

And you can’t take a whole lot at once to make up for years of deficiency. Too much at a time is as bad as too little, as I’ll explain in a moment.

Selenium is Vital from the First Days of Life

Research in Germany shows that even as the brain grows and develops right after birth, it depends on enzymes constructed with selenium to protect newly developed neurons. If baby doesn’t get enough selenium, those neurons are doomed.2

Other studies show that this selenium-dependent protection continues throughout life and into old age. The immune cells that roam the brain, according to European scientists, use enzymes containing selenium to help injured neurons recover.

The immune cells they’re talking about, called astrocytes, are better able to resist the oxidative stress that harms neurons. When injury occurs, the astrocytes arrive on the scene as first responders and deposit what are called “selenoproteins” to speed the healing process.3

Bad Mood, Failing Memory? Could be Your Selenium 

And a review study at Oklahoma State University confirms selenium’s importance in keeping memory intact and fighting off depression and other mood disorders.4 Although we think of these problems as mental or emotional, the researchers remind us that they’re often linked to oxidative stress, which is tempered by enzymes containing selenium. And they also add that selenium helps the thyroid function better. The thyroid supports healthy brain function.

Selenium’s role in staving off Alzheimer’s has been demonstrated in a large Asian study that shows selenium levels in the blood directly correlate with the risk for developing this type of dementia. Or, as the researchers point out in scientific jargon – selenium “had a consistent, dose-response relation with cognitive performance.”5

There’s more: An investigation in Brazil shows that folks with Alzheimer’s disease consistently have less selenium circulating in their blood than do people with normal brain function.6

When it comes to mood problems, a study in England found that older people who were depressed enjoyed significant mood improvements after taking 60 mcg of selenium for two months. Now, these were people whose blood levels of selenium were considered okay according to recognized guidelines. But the extra selenium still helped. In the tests, the participants took selenium as part of a multivitamin that also included 150 mcg of iodine.7

Take it Now to Prevent Future Problems

All that being said, if you want to be sure you have enough selenium, the sooner you look after getting this mineral into your diet the better. As I said before and as researchers in Germany have pointed out, there’s “no evidence for a role of Se in the treatment of AD.” No one is claiming it’s a “medicine” to treat Alzheimer’s disease.

But taking it before memory problems develop may keep your memory intact. As the German investigators put it, selenium has “a potential preventive relevance”8 against Alzheimer’s.

Brazil nuts are probably the richest food source of selenium. They’re also delicious and don’t require any preparation – my favorite qualities in a food! Organ meats and fish also are often rich in selenium.

Exercise caution if you take selenium supplements. Don’t megadose. The daily recommended amount for adults is 55 micrograms a day. This, of course, is merely the bare minimum. Nearly all standalone selenium supplements have 200 mcg. But don’t consume more than that.

If you overdo it, you may lose hair, suffer stomach pain, experience serious fatigue and develop spots on your nails. So be cautious with your intake.  It accumulates in the body so these symptoms may appear only after months or even years of overdosing. This means you won’t see the connection between the supplement and the changes in your body. Just keep things simple:  200 mcg a day is enough. If you eat a lot of Brazil nuts, you may need few or no selenium tablets.